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  r78576 | steven.bethard | 2010-03-02 00:38:09 -0800 (Tue, 02 Mar 2010) | 3 lines

  Initial commit of the argparse library, based on argparse 1.1.
  Docs still need some updating to make getopt and optparse match the wording promised in the PEP.
  There are also probably a number of :class:ArgumentParser etc. links that could be added to the argparse documentation.
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:mod:`argparse` -- Parser for command line options, arguments and sub-commands
==============================================================================
.. module:: argparse
:synopsis: Command-line option and argument parsing library.
.. moduleauthor:: Steven Bethard <steven.bethard@gmail.com>
.. versionadded:: 2.7
.. sectionauthor:: Steven Bethard <steven.bethard@gmail.com>
The :mod:`argparse` module makes it easy to write user friendly command line
interfaces. You define what arguments your program requires, and
:mod:`argparse` will figure out how to parse those out of ``sys.argv``. The
:mod:`argparse` module also automatically generates help and usage messages
based on the arguments you have defined, and issues errors when users give your
program invalid arguments.
Example
-------
As an example, the following code is a Python program that takes a list of
integers and produces either the sum or the max::
import argparse
parser = argparse.ArgumentParser(description='Process some integers.')
parser.add_argument('integers', metavar='N', type=int, nargs='+',
help='an integer for the accumulator')
parser.add_argument('--sum', dest='accumulate', action='store_const',
const=sum, default=max,
help='sum the integers (default: find the max)')
args = parser.parse_args()
print args.accumulate(args.integers)
Assuming the Python code above is saved into a file called ``prog.py``, it can
be run at the command line and provides useful help messages::
$ prog.py -h
usage: prog.py [-h] [--sum] N [N ...]
Process some integers.
positional arguments:
N an integer for the accumulator
optional arguments:
-h, --help show this help message and exit
--sum sum the integers (default: find the max)
When run with the appropriate arguments, it prints either the sum or the max of
the command-line integers::
$ prog.py 1 2 3 4
4
$ prog.py 1 2 3 4 --sum
10
If invalid arguments are passed in, it will issue an error::
$ prog.py a b c
usage: prog.py [-h] [--sum] N [N ...]
prog.py: error: argument N: invalid int value: 'a'
The following sections walk you through this example.
Creating a parser
^^^^^^^^^^^^^^^^^
Pretty much every script that uses the :mod:`argparse` module will start out by
creating an :class:`ArgumentParser` object::
>>> parser = argparse.ArgumentParser(description='Process some integers.')
The :class:`ArgumentParser` object will hold all the information necessary to
parse the command line into a more manageable form for your program.
Adding arguments
^^^^^^^^^^^^^^^^
Once you've created an :class:`ArgumentParser`, you'll want to fill it with
information about your program arguments. You typically do this by making calls
to the :meth:`add_argument` method. Generally, these calls tell the
:class:`ArgumentParser` how to take the strings on the command line and turn
them into objects for you. This information is stored and used when
:meth:`parse_args` is called. For example, if we add some arguments like this::
>>> parser.add_argument('integers', metavar='N', type=int, nargs='+',
... help='an integer for the accumulator')
>>> parser.add_argument('--sum', dest='accumulate', action='store_const',
... const=sum, default=max,
... help='sum the integers (default: find the max)')
when we later call :meth:`parse_args`, we can expect it to return an object
with two attributes, ``integers`` and ``accumulate``. The ``integers``
attribute will be a list of one or more ints, and the ``accumulate`` attribute
will be either the ``sum`` function, if ``--sum`` was specified at the command
line, or the ``max`` function if it was not.
Parsing arguments
^^^^^^^^^^^^^^^^^
Once an :class:`ArgumentParser` has been initialized with appropriate calls to
:meth:`add_argument`, it can be instructed to parse the command-line args by
calling the :meth:`parse_args` method. This will inspect the command-line,
convert each arg to the appropriate type and then invoke the appropriate
action. In most cases, this means a simple namespace object will be built up
from attributes parsed out of the command-line::
>>> parser.parse_args(['--sum', '7', '-1', '42'])
Namespace(accumulate=<built-in function sum>, integers=[7, -1, 42])
In a script, :meth:`parse_args` will typically be called with no arguments, and
the :class:`ArgumentParser` will automatically determine the command-line args
from ``sys.argv``. That's pretty much it. You're now ready to go write some
command line interfaces!
ArgumentParser objects
----------------------
.. class:: ArgumentParser([description], [epilog], [prog], [usage], [add_help], [argument_default], [parents], [prefix_chars], [conflict_handler], [formatter_class])
Create a new :class:`ArgumentParser` object. Each parameter has its own more
detailed description below, but in short they are:
* description_ - Text to display before the argument help.
* epilog_ - Text to display after the argument help.
* add_help_ - Add a -h/--help option to the parser. (default: True)
* argument_default_ - Set the global default value for arguments.
(default: None)
* parents_ - A list of :class:ArgumentParser objects whose arguments should
also be included.
* prefix_chars_ - The set of characters that prefix optional arguments.
(default: '-')
* fromfile_prefix_chars_ - The set of characters that prefix files from
which additional arguments should be read. (default: None)
* formatter_class_ - A class for customizing the help output.
* conflict_handler_ - Usually unnecessary, defines strategy for resolving
conflicting optionals.
* prog_ - Usually unnecessary, the name of the program
(default: ``sys.argv[0]``)
* usage_ - Usually unnecessary, the string describing the program usage
(default: generated)
The following sections describe how each of these are used.
description
^^^^^^^^^^^
Most calls to the ArgumentParser constructor will use the ``description=``
keyword argument. This argument gives a brief description of what the program
does and how it works. In help messages, the description is displayed between
the command-line usage string and the help messages for the various arguments::
>>> parser = argparse.ArgumentParser(description='A foo that bars')
>>> parser.print_help()
usage: argparse.py [-h]
A foo that bars
optional arguments:
-h, --help show this help message and exit
By default, the description will be line-wrapped so that it fits within the
given space. To change this behavior, see the formatter_class_ argument.
epilog
^^^^^^
Some programs like to display additional description of the program after the
description of the arguments. Such text can be specified using the ``epilog=``
argument to ArgumentParser::
>>> parser = argparse.ArgumentParser(
... description='A foo that bars',
... epilog="And that's how you'd foo a bar")
>>> parser.print_help()
usage: argparse.py [-h]
A foo that bars
optional arguments:
-h, --help show this help message and exit
And that's how you'd foo a bar
As with the description_ argument, the ``epilog=`` text is by default
line-wrapped, but this behavior can be adjusted with the formatter_class_
argument to ArgumentParser.
add_help
^^^^^^^^
By default, ArgumentParser objects add a ``-h/--help`` option which simply
displays the parser's help message. For example, consider a file named
``myprogram.py`` containing the following code::
import argparse
parser = argparse.ArgumentParser()
parser.add_argument('--foo', help='foo help')
args = parser.parse_args()
If ``-h`` or ``--help`` is supplied is at the command-line, the ArgumentParser
help will be printed::
$ python myprogram.py --help
usage: myprogram.py [-h] [--foo FOO]
optional arguments:
-h, --help show this help message and exit
--foo FOO foo help
Occasionally, it may be useful to disable the addition of this help option.
This can be achieved by passing ``False`` as the ``add_help=`` argument to
ArgumentParser::
>>> parser = argparse.ArgumentParser(prog='PROG', add_help=False)
>>> parser.add_argument('--foo', help='foo help')
>>> parser.print_help()
usage: PROG [--foo FOO]
optional arguments:
--foo FOO foo help
prefix_chars
^^^^^^^^^^^^
Most command-line options will use ``'-'`` as the prefix, e.g. ``-f/--foo``.
Parsers that need to support additional prefix characters, e.g. for options
like ``+f`` or ``/foo``, may specify them using the ``prefix_chars=`` argument
to the ArgumentParser constructor::
>>> parser = argparse.ArgumentParser(prog='PROG', prefix_chars='-+')
>>> parser.add_argument('+f')
>>> parser.add_argument('++bar')
>>> parser.parse_args('+f X ++bar Y'.split())
Namespace(bar='Y', f='X')
The ``prefix_chars=`` argument defaults to ``'-'``. Supplying a set of
characters that does not include ``'-'`` will cause ``-f/--foo`` options to be
disallowed.
fromfile_prefix_chars
^^^^^^^^^^^^^^^^^^^^^
Sometimes, e.g. for particularly long argument lists, it may make sense to
keep the list of arguments in a file rather than typing it out at the command
line. If the ``fromfile_prefix_chars=`` argument is given to the ArgumentParser
constructor, then arguments that start with any of the specified characters
will be treated as files, and will be replaced by the arguments they contain.
For example::
>>> open('args.txt', 'w').write('-f\nbar')
>>> parser = argparse.ArgumentParser(fromfile_prefix_chars='@')
>>> parser.add_argument('-f')
>>> parser.parse_args(['-f', 'foo', '@args.txt'])
Namespace(f='bar')
Arguments read from a file must by default be one per line (but see also
:meth:`convert_arg_line_to_args`) and are treated as if they were in the same
place as the original file referencing argument on the command line. So in the
example above, the expression ``['-f', 'foo', '@args.txt']`` is considered
equivalent to the expression ``['-f', 'foo', '-f', 'bar']``.
The ``fromfile_prefix_chars=`` argument defaults to ``None``, meaning that
arguments will never be treated as file references.
argument_default
^^^^^^^^^^^^^^^^
Generally, argument defaults are specified either by passing a default to
:meth:`add_argument` or by calling the :meth:`set_defaults` methods with a
specific set of name-value pairs. Sometimes however, it may be useful to
specify a single parser-wide default for arguments. This can be accomplished by
passing the ``argument_default=`` keyword argument to ArgumentParser. For
example, to globally suppress attribute creation on :meth:`parse_args` calls,
we supply ``argument_default=SUPPRESS``::
>>> parser = argparse.ArgumentParser(argument_default=argparse.SUPPRESS)
>>> parser.add_argument('--foo')
>>> parser.add_argument('bar', nargs='?')
>>> parser.parse_args(['--foo', '1', 'BAR'])
Namespace(bar='BAR', foo='1')
>>> parser.parse_args([])
Namespace()
parents
^^^^^^^
Sometimes, several parsers share a common set of arguments. Rather than
repeating the definitions of these arguments, you can define a single parser
with all the shared arguments and then use the ``parents=`` argument to
ArgumentParser to have these "inherited". The ``parents=`` argument takes a
list of ArgumentParser objects, collects all the positional and optional
actions from them, and adds these actions to the ArgumentParser object being
constructed::
>>> parent_parser = argparse.ArgumentParser(add_help=False)
>>> parent_parser.add_argument('--parent', type=int)
>>> foo_parser = argparse.ArgumentParser(parents=[parent_parser])
>>> foo_parser.add_argument('foo')
>>> foo_parser.parse_args(['--parent', '2', 'XXX'])
Namespace(foo='XXX', parent=2)
>>> bar_parser = argparse.ArgumentParser(parents=[parent_parser])
>>> bar_parser.add_argument('--bar')
>>> bar_parser.parse_args(['--bar', 'YYY'])
Namespace(bar='YYY', parent=None)
Note that most parent parsers will specify ``add_help=False``. Otherwise, the
ArgumentParser will see two ``-h/--help`` options (one in the parent and one in
the child) and raise an error.
formatter_class
^^^^^^^^^^^^^^^
ArgumentParser objects allow the help formatting to be customized by specifying
an alternate formatting class. Currently, there are three such classes:
``argparse.RawDescriptionHelpFormatter``, ``argparse.RawTextHelpFormatter`` and
``argparse.ArgumentDefaultsHelpFormatter``. The first two allow more control
over how textual descriptions are displayed, while the last automatically adds
information about argument default values.
By default, ArgumentParser objects line-wrap the description_ and epilog_ texts
in command-line help messages::
>>> parser = argparse.ArgumentParser(
... prog='PROG',
... description='''this description
... was indented weird
... but that is okay''',
... epilog='''
... likewise for this epilog whose whitespace will
... be cleaned up and whose words will be wrapped
... across a couple lines''')
>>> parser.print_help()
usage: PROG [-h]
this description was indented weird but that is okay
optional arguments:
-h, --help show this help message and exit
likewise for this epilog whose whitespace will be cleaned up and whose words
will be wrapped across a couple lines
When you have description_ and epilog_ that is already correctly formatted and
should not be line-wrapped, you can indicate this by passing
``argparse.RawDescriptionHelpFormatter`` as the ``formatter_class=`` argument
to ArgumentParser::
>>> parser = argparse.ArgumentParser(
... prog='PROG',
... formatter_class=argparse.RawDescriptionHelpFormatter,
... description=textwrap.dedent('''\
... Please do not mess up this text!
... --------------------------------
... I have indented it
... exactly the way
... I want it
... '''))
>>> parser.print_help()
usage: PROG [-h]
Please do not mess up this text!
--------------------------------
I have indented it
exactly the way
I want it
optional arguments:
-h, --help show this help message and exit
If you want to maintain whitespace for all sorts of help text (including
argument descriptions), you can use ``argparse.RawTextHelpFormatter``.
The other formatter class available,
``argparse.ArgumentDefaultsHelpFormatter``, will add information about the
default value of each of the arguments::
>>> parser = argparse.ArgumentParser(
... prog='PROG',
... formatter_class=argparse.ArgumentDefaultsHelpFormatter)
>>> parser.add_argument('--foo', type=int, default=42, help='FOO!')
>>> parser.add_argument('bar', nargs='*', default=[1, 2, 3], help='BAR!')
>>> parser.print_help()
usage: PROG [-h] [--foo FOO] [bar [bar ...]]
positional arguments:
bar BAR! (default: [1, 2, 3])
optional arguments:
-h, --help show this help message and exit
--foo FOO FOO! (default: 42)
conflict_handler
^^^^^^^^^^^^^^^^
ArgumentParser objects do not allow two actions with the same option string.
By default, ArgumentParser objects will raise an exception if you try to create
an argument with an option string that is already in use::
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-f', '--foo', help='old foo help')
>>> parser.add_argument('--foo', help='new foo help')
Traceback (most recent call last):
..
ArgumentError: argument --foo: conflicting option string(s): --foo
Sometimes (e.g. when using parents_) it may be useful to simply override any
older arguments with the same option string. To get this behavior, the value
``'resolve'`` can be supplied to the ``conflict_handler=`` argument of
ArgumentParser::
>>> parser = argparse.ArgumentParser(prog='PROG', conflict_handler='resolve')
>>> parser.add_argument('-f', '--foo', help='old foo help')
>>> parser.add_argument('--foo', help='new foo help')
>>> parser.print_help()
usage: PROG [-h] [-f FOO] [--foo FOO]
optional arguments:
-h, --help show this help message and exit
-f FOO old foo help
--foo FOO new foo help
Note that ArgumentParser objects only remove an action if all of its option
strings are overridden. So, in the example above, the old ``-f/--foo`` action
is retained as the ``-f`` action, because only the ``--foo`` option string was
overridden.
prog
^^^^
By default, ArgumentParser objects use ``sys.argv[0]`` to determine how to
display the name of the program in help messages. This default is almost always
what you want because it will make the help messages match what your users have
typed at the command line. For example, consider a file named ``myprogram.py``
with the following code::
import argparse
parser = argparse.ArgumentParser()
parser.add_argument('--foo', help='foo help')
args = parser.parse_args()
The help for this program will display ``myprogram.py`` as the program name
(regardless of where the program was invoked from)::
$ python myprogram.py --help
usage: myprogram.py [-h] [--foo FOO]
optional arguments:
-h, --help show this help message and exit
--foo FOO foo help
$ cd ..
$ python subdir\myprogram.py --help
usage: myprogram.py [-h] [--foo FOO]
optional arguments:
-h, --help show this help message and exit
--foo FOO foo help
To change this default behavior, another value can be supplied using the
``prog=`` argument to ArgumentParser::
>>> parser = argparse.ArgumentParser(prog='myprogram')
>>> parser.print_help()
usage: myprogram [-h]
optional arguments:
-h, --help show this help message and exit
Note that the program name, whether determined from ``sys.argv[0]`` or from the
``prog=`` argument, is available to help messages using the ``%(prog)s`` format
specifier.
::
>>> parser = argparse.ArgumentParser(prog='myprogram')
>>> parser.add_argument('--foo', help='foo of the %(prog)s program')
>>> parser.print_help()
usage: myprogram [-h] [--foo FOO]
optional arguments:
-h, --help show this help message and exit
--foo FOO foo of the myprogram program
usage
^^^^^
By default, ArgumentParser objects calculate the usage message from the
arguments it contains::
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('--foo', nargs='?', help='foo help')
>>> parser.add_argument('bar', nargs='+', help='bar help')
>>> parser.print_help()
usage: PROG [-h] [--foo [FOO]] bar [bar ...]
positional arguments:
bar bar help
optional arguments:
-h, --help show this help message and exit
--foo [FOO] foo help
If the default usage message is not appropriate for your application, you can
supply your own usage message using the ``usage=`` keyword argument to
ArgumentParser::
>>> parser = argparse.ArgumentParser(prog='PROG', usage='%(prog)s [options]')
>>> parser.add_argument('--foo', nargs='?', help='foo help')
>>> parser.add_argument('bar', nargs='+', help='bar help')
>>> parser.print_help()
usage: PROG [options]
positional arguments:
bar bar help
optional arguments:
-h, --help show this help message and exit
--foo [FOO] foo help
Note you can use the ``%(prog)s`` format specifier to fill in the program name
in your usage messages.
The add_argument() method
-------------------------
.. method:: add_argument(name or flags..., [action], [nargs], [const], [default], [type], [choices], [required], [help], [metavar], [dest])
Define how a single command line argument should be parsed. Each parameter
has its own more detailed description below, but in short they are:
* `name or flags`_ - Either a name or a list of option strings, e.g. ``foo``
or ``-f, --foo``
* action_ - The basic type of action to be taken when this argument is
encountered at the command-line.
* nargs_ - The number of command-line arguments that should be consumed.
* const_ - A constant value required by some action_ and nargs_ selections.
* default_ - The value produced if the argument is absent from the
command-line.
* type_ - The type to which the command-line arg should be converted.
* choices_ - A container of the allowable values for the argument.
* required_ - Whether or not the command-line option may be omitted
(optionals only).
* help_ - A brief description of what the argument does.
* metavar_ - A name for the argument in usage messages.
* dest_ - The name of the attribute to be added to the object returned by
:meth:`parse_args`.
The following sections describe how each of these are used.
name or flags
^^^^^^^^^^^^^
The :meth:`add_argument` method needs to know whether you're expecting an
optional argument, e.g. ``-f`` or ``--foo``, or a positional argument, e.g. a
list of filenames. The first arguments passed to :meth:`add_argument` must
therefore be either a series of flags, or a simple argument name. For example,
an optional argument could be created like::
>>> parser.add_argument('-f', '--foo')
while a positional argument could be created like::
>>> parser.add_argument('bar')
When :meth:`parse_args` is called, optional arguments will be identified by the
``-`` prefix, and the remaining arguments will be assumed to be positional::
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-f', '--foo')
>>> parser.add_argument('bar')
>>> parser.parse_args(['BAR'])
Namespace(bar='BAR', foo=None)
>>> parser.parse_args(['BAR', '--foo', 'FOO'])
Namespace(bar='BAR', foo='FOO')
>>> parser.parse_args(['--foo', 'FOO'])
usage: PROG [-h] [-f FOO] bar
PROG: error: too few arguments
action
^^^^^^
:class:`ArgumentParser` objects associate command-line args with actions. These
actions can do just about anything with the command-line args associated with
them, though most actions simply add an attribute to the object returned by
:meth:`parse_args`. When you specify a new argument using the
:meth:`add_argument` method, you can indicate how the command-line args should
be handled by specifying the ``action`` keyword argument. The supported actions
are:
* ``'store'`` - This just stores the argument's value. This is the default
action. For example::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo')
>>> parser.parse_args('--foo 1'.split())
Namespace(foo='1')
* ``'store_const'`` - This stores the value specified by the const_ keyword
argument. Note that the const_ keyword argument defaults to ``None``, so
you'll almost always need to provide a value for it. The ``'store_const'``
action is most commonly used with optional arguments that specify some sort
of flag. For example::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', action='store_const', const=42)
>>> parser.parse_args('--foo'.split())
Namespace(foo=42)
* ``'store_true'`` and ``'store_false'`` - These store the values ``True`` and
``False`` respectively. These are basically special cases of
``'store_const'``. For example::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', action='store_true')
>>> parser.add_argument('--bar', action='store_false')
>>> parser.parse_args('--foo --bar'.split())
Namespace(bar=False, foo=True)
* ``'append'`` - This stores a list, and appends each argument value to the
list. This is useful when you want to allow an option to be specified
multiple times. Example usage::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', action='append')
>>> parser.parse_args('--foo 1 --foo 2'.split())
Namespace(foo=['1', '2'])
* ``'append_const'`` - This stores a list, and appends the value specified by
the const_ keyword argument to the list. Note that the const_ keyword
argument defaults to ``None``, so you'll almost always need to provide a
value for it. The ``'append_const'`` action is typically useful when you
want multiple arguments to store constants to the same list, for example::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--str', dest='types', action='append_const', const=str)
>>> parser.add_argument('--int', dest='types', action='append_const', const=int)
>>> parser.parse_args('--str --int'.split())
Namespace(types=[<type 'str'>, <type 'int'>])
* ``'version'`` - This expects a ``version=`` keyword argument in the
:meth:`add_argument` call, and prints version information and exits when
invoked.
>>> import argparse
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-v', '--version', action='version', version='%(prog)s 2.0')
>>> parser.parse_args(['-v'])
PROG 2.0
You can also specify an arbitrary action by passing an object that implements
the Action API. The easiest way to do this is to extend ``argparse.Action``,
supplying an appropriate ``__call__`` method. The ``__call__`` method accepts
four parameters:
* ``parser`` - The ArgumentParser object which contains this action.
* ``namespace`` - The namespace object that will be returned by
:meth:`parse_args`. Most actions add an attribute to this object.
* ``values`` - The associated command-line args, with any type-conversions
applied. (Type-conversions are specified with the type_ keyword argument to
:meth:`add_argument`.
* ``option_string`` - The option string that was used to invoke this action.
The ``option_string`` argument is optional, and will be absent if the action
is associated with a positional argument.
So for example::
>>> class FooAction(argparse.Action):
... def __call__(self, parser, namespace, values, option_string=None):
... print '%r %r %r' % (namespace, values, option_string)
... setattr(namespace, self.dest, values)
...
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', action=FooAction)
>>> parser.add_argument('bar', action=FooAction)
>>> args = parser.parse_args('1 --foo 2'.split())
Namespace(bar=None, foo=None) '1' None
Namespace(bar='1', foo=None) '2' '--foo'
>>> args
Namespace(bar='1', foo='2')
nargs
^^^^^
ArgumentParser objects usually associate a single command-line argument with a
single action to be taken. In the situations where you'd like to associate a
different number of command-line arguments with a single action, you can use
the ``nargs`` keyword argument to :meth:`add_argument`. The supported values
are:
* N (an integer). N args from the command-line will be gathered together into
a list. For example::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', nargs=2)
>>> parser.add_argument('bar', nargs=1)
>>> parser.parse_args('c --foo a b'.split())
Namespace(bar=['c'], foo=['a', 'b'])
Note that ``nargs=1`` produces a list of one item. This is different from
the default, in which the item is produced by itself.
* ``'?'``. One arg will be consumed from the command-line if possible, and
produced as a single item. If no command-line arg is present, the value from
default_ will be produced. Note that for optional arguments, there is an
additional case - the option string is present but not followed by a
command-line arg. In this case the value from const_ will be produced. Some
examples to illustrate this::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', nargs='?', const='c', default='d')
>>> parser.add_argument('bar', nargs='?', default='d')
>>> parser.parse_args('XX --foo YY'.split())
Namespace(bar='XX', foo='YY')
>>> parser.parse_args('XX --foo'.split())
Namespace(bar='XX', foo='c')
>>> parser.parse_args(''.split())
Namespace(bar='d', foo='d')
One of the more common uses of ``nargs='?'`` is to allow optional input and
output files::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('infile', nargs='?', type=argparse.FileType('r'), default=sys.stdin)
>>> parser.add_argument('outfile', nargs='?', type=argparse.FileType('w'), default=sys.stdout)
>>> parser.parse_args(['input.txt', 'output.txt'])
Namespace(infile=<open file 'input.txt', mode 'r' at 0x...>, outfile=<open file 'output.txt', mode 'w' at 0x...>)
>>> parser.parse_args([])
Namespace(infile=<open file '<stdin>', mode 'r' at 0x...>, outfile=<open file '<stdout>', mode 'w' at 0x...>)
* ``'*'``. All command-line args present are gathered into a list. Note that
it generally doesn't make much sense to have more than one positional
argument with ``nargs='*'``, but multiple optional arguments with
``nargs='*'`` is possible. For example::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', nargs='*')
>>> parser.add_argument('--bar', nargs='*')
>>> parser.add_argument('baz', nargs='*')
>>> parser.parse_args('a b --foo x y --bar 1 2'.split())
Namespace(bar=['1', '2'], baz=['a', 'b'], foo=['x', 'y'])
* ``'+'``. Just like ``'*'``, all command-line args present are gathered into a
list. Additionally, an error message will be generated if there wasn't at
least one command-line arg present. For example::
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('foo', nargs='+')
>>> parser.parse_args('a b'.split())
Namespace(foo=['a', 'b'])
>>> parser.parse_args(''.split())
usage: PROG [-h] foo [foo ...]
PROG: error: too few arguments
If the ``nargs`` keyword argument is not provided, the number of args consumed
is determined by the action_. Generally this means a single command-line arg
will be consumed and a single item (not a list) will be produced.
const
^^^^^
The ``const`` argument of :meth:`add_argument` is used to hold constant values
that are not read from the command line but are required for the various
ArgumentParser actions. The two most common uses of it are:
* When :meth:`add_argument` is called with ``action='store_const'`` or
``action='append_const'``. These actions add the ``const`` value to one of
the attributes of the object returned by :meth:`parse_args`. See the action_
description for examples.
* When :meth:`add_argument` is called with option strings (like ``-f`` or
``--foo``) and ``nargs='?'``. This creates an optional argument that can be
followed by zero or one command-line args. When parsing the command-line, if
the option string is encountered with no command-line arg following it, the
value of ``const`` will be assumed instead. See the nargs_ description for
examples.
The ``const`` keyword argument defaults to ``None``.
default
^^^^^^^
All optional arguments and some positional arguments may be omitted at the
command-line. The ``default`` keyword argument of :meth:`add_argument`, whose
value defaults to ``None``, specifies what value should be used if the
command-line arg is not present. For optional arguments, the ``default`` value
is used when the option string was not present at the command line::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', default=42)
>>> parser.parse_args('--foo 2'.split())
Namespace(foo='2')
>>> parser.parse_args(''.split())
Namespace(foo=42)
For positional arguments with nargs_ ``='?'`` or ``'*'``, the ``default`` value
is used when no command-line arg was present::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('foo', nargs='?', default=42)
>>> parser.parse_args('a'.split())
Namespace(foo='a')
>>> parser.parse_args(''.split())
Namespace(foo=42)
If you don't want to see an attribute when an option was not present at the
command line, you can supply ``default=argparse.SUPPRESS``::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', default=argparse.SUPPRESS)
>>> parser.parse_args([])
Namespace()
>>> parser.parse_args(['--foo', '1'])
Namespace(foo='1')
type
^^^^
By default, ArgumentParser objects read command-line args in as simple strings.
However, quite often the command-line string should instead be interpreted as
another type, e.g. ``float``, ``int`` or ``file``. The ``type`` keyword
argument of :meth:`add_argument` allows any necessary type-checking and
type-conversions to be performed. Many common builtin types can be used
directly as the value of the ``type`` argument::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('foo', type=int)
>>> parser.add_argument('bar', type=file)
>>> parser.parse_args('2 temp.txt'.split())
Namespace(bar=<open file 'temp.txt', mode 'r' at 0x...>, foo=2)
To ease the use of various types of files, the argparse module provides the
factory FileType which takes the ``mode=`` and ``bufsize=`` arguments of the
``file`` object. For example, ``FileType('w')`` can be used to create a
writable file::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('bar', type=argparse.FileType('w'))
>>> parser.parse_args(['out.txt'])
Namespace(bar=<open file 'out.txt', mode 'w' at 0x...>)
If you need to do some special type-checking or type-conversions, you can
provide your own types by passing to ``type=`` a callable that takes a single
string argument and returns the type-converted value::
>>> def perfect_square(string):
... value = int(string)
... sqrt = math.sqrt(value)
... if sqrt != int(sqrt):
... msg = "%r is not a perfect square" % string
... raise argparse.ArgumentTypeError(msg)
... return value
...
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('foo', type=perfect_square)
>>> parser.parse_args('9'.split())
Namespace(foo=9)
>>> parser.parse_args('7'.split())
usage: PROG [-h] foo
PROG: error: argument foo: '7' is not a perfect square
Note that if your type-checking function is just checking for a particular set
of values, it may be more convenient to use the choices_ keyword argument::
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('foo', type=int, choices=xrange(5, 10))
>>> parser.parse_args('7'.split())
Namespace(foo=7)
>>> parser.parse_args('11'.split())
usage: PROG [-h] {5,6,7,8,9}
PROG: error: argument foo: invalid choice: 11 (choose from 5, 6, 7, 8, 9)
See the choices_ section for more details.
choices
^^^^^^^
Some command-line args should be selected from a restricted set of values.
ArgumentParser objects can be told about such sets of values by passing a
container object as the ``choices`` keyword argument to :meth:`add_argument`.
When the command-line is parsed with :meth:`parse_args`, arg values will be
checked, and an error message will be displayed if the arg was not one of the
acceptable values::
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('foo', choices='abc')
>>> parser.parse_args('c'.split())
Namespace(foo='c')
>>> parser.parse_args('X'.split())
usage: PROG [-h] {a,b,c}
PROG: error: argument foo: invalid choice: 'X' (choose from 'a', 'b', 'c')
Note that inclusion in the ``choices`` container is checked after any type_
conversions have been performed, so the type of the objects in the ``choices``
container should match the type_ specified::
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('foo', type=complex, choices=[1, 1j])
>>> parser.parse_args('1j'.split())
Namespace(foo=1j)
>>> parser.parse_args('-- -4'.split())
usage: PROG [-h] {1,1j}
PROG: error: argument foo: invalid choice: (-4+0j) (choose from 1, 1j)
Any object that supports the ``in`` operator can be passed as the ``choices``
value, so ``dict`` objects, ``set`` objects, custom containers, etc. are all
supported.
required
^^^^^^^^
In general, the argparse module assumes that flags like ``-f`` and ``--bar``
indicate *optional* arguments, which can always be omitted at the command-line.
To change this behavior, i.e. to make an option *required*, the value ``True``
should be specified for the ``required=`` keyword argument to
:meth:`add_argument`::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', required=True)
>>> parser.parse_args(['--foo', 'BAR'])
Namespace(foo='BAR')
>>> parser.parse_args([])
usage: argparse.py [-h] [--foo FOO]
argparse.py: error: option --foo is required
As the example shows, if an option is marked as ``required``, :meth:`parse_args`
will report an error if that option is not present at the command line.
**Warning:** Required options are generally considered bad form - normal users
expect *options* to be *optional*. You should avoid the use of required options
whenever possible.
help
^^^^
A great command-line interface isn't worth anything if your users can't figure
out which option does what. So for the end-users, ``help`` is probably the
most important argument to include in your :meth:`add_argument` calls. The
``help`` value should be a string containing a brief description of what the
argument specifies. When a user requests help (usually by using ``-h`` or
``--help`` at the command-line), these ``help`` descriptions will be displayed
with each argument::
>>> parser = argparse.ArgumentParser(prog='frobble')
>>> parser.add_argument('--foo', action='store_true',
... help='foo the bars before frobbling')
>>> parser.add_argument('bar', nargs='+',
... help='one of the bars to be frobbled')
>>> parser.parse_args('-h'.split())
usage: frobble [-h] [--foo] bar [bar ...]
positional arguments:
bar one of the bars to be frobbled
optional arguments:
-h, --help show this help message and exit
--foo foo the bars before frobbling
The ``help`` strings can include various format specifiers to avoid repetition
of things like the program name or the argument default_. The available
specifiers include the program name, ``%(prog)s`` and most keyword arguments to
:meth:`add_argument`, e.g. ``%(default)s``, ``%(type)s``, etc.::
>>> parser = argparse.ArgumentParser(prog='frobble')
>>> parser.add_argument('bar', nargs='?', type=int, default=42,
... help='the bar to %(prog)s (default: %(default)s)')
>>> parser.print_help()
usage: frobble [-h] [bar]
positional arguments:
bar the bar to frobble (default: 42)
optional arguments:
-h, --help show this help message and exit
metavar
^^^^^^^
When ArgumentParser objects generate help messages, they need some way to refer
to each expected argument. By default, ArgumentParser objects use the dest_
value as the "name" of each object. By default, for positional argument
actions, the dest_ value is used directly, and for optional argument actions,
the dest_ value is uppercased. So if we have a single positional argument with
``dest='bar'``, that argument will be referred to as ``bar``. And if we have a
single optional argument ``--foo`` that should be followed by a single
command-line arg, that arg will be referred to as ``FOO``. You can see this
behavior in the example below::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo')
>>> parser.add_argument('bar')
>>> parser.parse_args('X --foo Y'.split())
Namespace(bar='X', foo='Y')
>>> parser.print_help()
usage: [-h] [--foo FOO] bar
positional arguments:
bar
optional arguments:
-h, --help show this help message and exit
--foo FOO
If you would like to provide a different name for your argument in help
messages, you can supply a value for the ``metavar`` keyword argument to
:meth:`add_argument`::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', metavar='YYY')
>>> parser.add_argument('bar', metavar='XXX')
>>> parser.parse_args('X --foo Y'.split())
Namespace(bar='X', foo='Y')
>>> parser.print_help()
usage: [-h] [--foo YYY] XXX
positional arguments:
XXX
optional arguments:
-h, --help show this help message and exit
--foo YYY
Note that ``metavar`` only changes the *displayed* name - the name of the
attribute on the :meth:`parse_args` object is still determined by the dest_
value.
Different values of ``nargs`` may cause the metavar to be used multiple times.
If you'd like to specify a different display name for each of the arguments,
you can provide a tuple to ``metavar``::
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-x', nargs=2)
>>> parser.add_argument('--foo', nargs=2, metavar=('bar', 'baz'))
>>> parser.print_help()
usage: PROG [-h] [-x X X] [--foo bar baz]
optional arguments:
-h, --help show this help message and exit
-x X X
--foo bar baz
dest
^^^^
Most ArgumentParser actions add some value as an attribute of the object
returned by :meth:`parse_args`. The name of this attribute is determined by the
``dest`` keyword argument of :meth:`add_argument`. For positional argument
actions, ``dest`` is normally supplied as the first argument to
:meth:`add_argument`::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('bar')
>>> parser.parse_args('XXX'.split())
Namespace(bar='XXX')
For optional argument actions, the value of ``dest`` is normally inferred from
the option strings. ArgumentParser objects generate the value of ``dest`` by
taking the first long option string and stripping away the initial ``'--'``
string. If no long option strings were supplied, ``dest`` will be derived from
the first short option string by stripping the initial ``'-'`` character. Any
internal ``'-'`` characters will be converted to ``'_'`` characters to make
sure the string is a valid attribute name. The examples below illustrate this
behavior::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('-f', '--foo-bar', '--foo')
>>> parser.add_argument('-x', '-y')
>>> parser.parse_args('-f 1 -x 2'.split())
Namespace(foo_bar='1', x='2')
>>> parser.parse_args('--foo 1 -y 2'.split())
Namespace(foo_bar='1', x='2')
If you would like to use a different attribute name from the one automatically
inferred by the ArgumentParser, you can supply it with an explicit ``dest``
parameter::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', dest='bar')
>>> parser.parse_args('--foo XXX'.split())
Namespace(bar='XXX')
The parse_args() method
-----------------------
.. method:: parse_args([args], [namespace])
Convert the strings to objects and assign them as attributes of the
namespace. Return the populated namespace.
Previous calls to :meth:`add_argument` determine exactly what objects are
created and how they are assigned. See the documentation for
:meth:`add_argument` for details.
By default, the arg strings are taken from ``sys.argv``, and a new empty
``Namespace`` object is created for the attributes.
Option value syntax
^^^^^^^^^^^^^^^^^^^
The :meth:`parse_args` method supports several ways of specifying the value of
an option (if it takes one). In the simplest case, the option and its value are
passed as two separate arguments::
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-x')
>>> parser.add_argument('--foo')
>>> parser.parse_args('-x X'.split())
Namespace(foo=None, x='X')
>>> parser.parse_args('--foo FOO'.split())
Namespace(foo='FOO', x=None)
For long options (options with names longer than a single character), you may
also pass the option and value as a single command line argument, using ``=``
to separate them::
>>> parser.parse_args('--foo=FOO'.split())
Namespace(foo='FOO', x=None)
For short options (options only one character long), you may simply concatenate
the option and its value::
>>> parser.parse_args('-xX'.split())
Namespace(foo=None, x='X')
You can also combine several short options together, using only a single ``-``
prefix, as long as only the last option (or none of them) requires a value::
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-x', action='store_true')
>>> parser.add_argument('-y', action='store_true')
>>> parser.add_argument('-z')
>>> parser.parse_args('-xyzZ'.split())
Namespace(x=True, y=True, z='Z')
Invalid arguments
^^^^^^^^^^^^^^^^^
While parsing the command-line, ``parse_args`` checks for a variety of errors,
including ambiguous options, invalid types, invalid options, wrong number of
positional arguments, etc. When it encounters such an error, it exits and
prints the error along with a usage message::
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('--foo', type=int)
>>> parser.add_argument('bar', nargs='?')
>>> # invalid type
>>> parser.parse_args(['--foo', 'spam'])
usage: PROG [-h] [--foo FOO] [bar]
PROG: error: argument --foo: invalid int value: 'spam'
>>> # invalid option
>>> parser.parse_args(['--bar'])
usage: PROG [-h] [--foo FOO] [bar]
PROG: error: no such option: --bar
>>> # wrong number of arguments
>>> parser.parse_args(['spam', 'badger'])
usage: PROG [-h] [--foo FOO] [bar]
PROG: error: extra arguments found: badger
Arguments containing ``"-"``
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The ``parse_args`` method attempts to give errors whenever the user has clearly
made a mistake, but some situations are inherently ambiguous. For example, the
command-line arg ``'-1'`` could either be an attempt to specify an option or an
attempt to provide a positional argument. The ``parse_args`` method is cautious
here: positional arguments may only begin with ``'-'`` if they look like
negative numbers and there are no options in the parser that look like negative
numbers::
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-x')
>>> parser.add_argument('foo', nargs='?')
>>> # no negative number options, so -1 is a positional argument
>>> parser.parse_args(['-x', '-1'])
Namespace(foo=None, x='-1')
>>> # no negative number options, so -1 and -5 are positional arguments
>>> parser.parse_args(['-x', '-1', '-5'])
Namespace(foo='-5', x='-1')
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-1', dest='one')
>>> parser.add_argument('foo', nargs='?')
>>> # negative number options present, so -1 is an option
>>> parser.parse_args(['-1', 'X'])
Namespace(foo=None, one='X')
>>> # negative number options present, so -2 is an option
>>> parser.parse_args(['-2'])
usage: PROG [-h] [-1 ONE] [foo]
PROG: error: no such option: -2
>>> # negative number options present, so both -1s are options
>>> parser.parse_args(['-1', '-1'])
usage: PROG [-h] [-1 ONE] [foo]
PROG: error: argument -1: expected one argument
If you have positional arguments that must begin with ``'-'`` and don't look
like negative numbers, you can insert the pseudo-argument ``'--'`` which tells
``parse_args`` that everything after that is a positional argument::
>>> parser.parse_args(['--', '-f'])
Namespace(foo='-f', one=None)
Argument abbreviations
^^^^^^^^^^^^^^^^^^^^^^
The :meth:`parse_args` method allows you to abbreviate long options if the
abbreviation is unambiguous::
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('-bacon')
>>> parser.add_argument('-badger')
>>> parser.parse_args('-bac MMM'.split())
Namespace(bacon='MMM', badger=None)
>>> parser.parse_args('-bad WOOD'.split())
Namespace(bacon=None, badger='WOOD')
>>> parser.parse_args('-ba BA'.split())
usage: PROG [-h] [-bacon BACON] [-badger BADGER]
PROG: error: ambiguous option: -ba could match -badger, -bacon
As you can see above, you will get an error if you pick a prefix that could
refer to more than one option.
Beyond ``sys.argv``
^^^^^^^^^^^^^^^^^^^
Sometimes it may be useful to have an ArgumentParser parse args other than
those of ``sys.argv``. This can be accomplished by passing a list of strings
to ``parse_args``. You may have noticed that the examples in the argparse
documentation have made heavy use of this calling style - it is much easier
to use at the interactive prompt::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument(
... 'integers', metavar='int', type=int, choices=xrange(10),
... nargs='+', help='an integer in the range 0..9')
>>> parser.add_argument(
... '--sum', dest='accumulate', action='store_const', const=sum,
... default=max, help='sum the integers (default: find the max)')
>>> parser.parse_args(['1', '2', '3', '4'])
Namespace(accumulate=<built-in function max>, integers=[1, 2, 3, 4])
>>> parser.parse_args('1 2 3 4 --sum'.split())
Namespace(accumulate=<built-in function sum>, integers=[1, 2, 3, 4])
Custom namespaces
^^^^^^^^^^^^^^^^^
It may also be useful to have an ArgumentParser assign attributes to an already
existing object, rather than the newly-created Namespace object that is
normally used. This can be achieved by specifying the ``namespace=`` keyword
argument::
>>> class C(object):
... pass
...
>>> c = C()
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo')
>>> parser.parse_args(args=['--foo', 'BAR'], namespace=c)
>>> c.foo
'BAR'
Other utilities
---------------
Sub-commands
^^^^^^^^^^^^
.. method:: add_subparsers()
A lot of programs split up their functionality into a number of
sub-commands, for example, the ``svn`` program can invoke sub-commands like
``svn checkout``, ``svn update``, ``svn commit``, etc. Splitting up
functionality this way can be a particularly good idea when a program
performs several different functions which require different kinds of
command-line arguments. ArgumentParser objects support the creation of such
sub-commands with the :meth:`add_subparsers` method. The
:meth:`add_subparsers` method is normally called with no arguments and
returns an special action object. This object has a single method,
``add_parser``, which takes a command name and any ArgumentParser
constructor arguments, and returns an ArgumentParser object that can be
modified as usual.
Some example usage::
>>> # create the top-level parser
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> parser.add_argument('--foo', action='store_true', help='foo help')
>>> subparsers = parser.add_subparsers(help='sub-command help')
>>>
>>> # create the parser for the "a" command
>>> parser_a = subparsers.add_parser('a', help='a help')
>>> parser_a.add_argument('bar', type=int, help='bar help')
>>>
>>> # create the parser for the "b" command
>>> parser_b = subparsers.add_parser('b', help='b help')
>>> parser_b.add_argument('--baz', choices='XYZ', help='baz help')
>>>
>>> # parse some arg lists
>>> parser.parse_args(['a', '12'])
Namespace(bar=12, foo=False)
>>> parser.parse_args(['--foo', 'b', '--baz', 'Z'])
Namespace(baz='Z', foo=True)
Note that the object returned by :meth:`parse_args` will only contain
attributes for the main parser and the subparser that was selected by the
command line (and not any other subparsers). So in the example above, when
the ``"a"`` command is specified, only the ``foo`` and ``bar`` attributes
are present, and when the ``"b"`` command is specified, only the ``foo`` and
``baz`` attributes are present.
Similarly, when a help message is requested from a subparser, only the help
for that particular parser will be printed. The help message will not
include parent parser or sibling parser messages. (You can however supply a
help message for each subparser command by suppling the ``help=`` argument
to ``add_parser`` as above.)
::
>>> parser.parse_args(['--help'])
usage: PROG [-h] [--foo] {a,b} ...
positional arguments:
{a,b} sub-command help
a a help
b b help
optional arguments:
-h, --help show this help message and exit
--foo foo help
>>> parser.parse_args(['a', '--help'])
usage: PROG a [-h] bar
positional arguments:
bar bar help
optional arguments:
-h, --help show this help message and exit
>>> parser.parse_args(['b', '--help'])
usage: PROG b [-h] [--baz {X,Y,Z}]
optional arguments:
-h, --help show this help message and exit
--baz {X,Y,Z} baz help
The :meth:`add_subparsers` method also supports ``title`` and
``description`` keyword arguments. When either is present, the subparser's
commands will appear in their own group in the help output. For example::
>>> parser = argparse.ArgumentParser()
>>> subparsers = parser.add_subparsers(title='subcommands',
... description='valid subcommands',
... help='additional help')
>>> subparsers.add_parser('foo')
>>> subparsers.add_parser('bar')
>>> parser.parse_args(['-h'])
usage: [-h] {foo,bar} ...
optional arguments:
-h, --help show this help message and exit
subcommands:
valid subcommands
{foo,bar} additional help
One particularly effective way of handling sub-commands is to combine the
use of the :meth:`add_subparsers` method with calls to :meth:`set_defaults`
so that each subparser knows which Python function it should execute. For
example::
>>> # sub-command functions
>>> def foo(args):
... print args.x * args.y
...
>>> def bar(args):
... print '((%s))' % args.z
...
>>> # create the top-level parser
>>> parser = argparse.ArgumentParser()
>>> subparsers = parser.add_subparsers()
>>>
>>> # create the parser for the "foo" command
>>> parser_foo = subparsers.add_parser('foo')
>>> parser_foo.add_argument('-x', type=int, default=1)
>>> parser_foo.add_argument('y', type=float)
>>> parser_foo.set_defaults(func=foo)
>>>
>>> # create the parser for the "bar" command
>>> parser_bar = subparsers.add_parser('bar')
>>> parser_bar.add_argument('z')
>>> parser_bar.set_defaults(func=bar)
>>>
>>> # parse the args and call whatever function was selected
>>> args = parser.parse_args('foo 1 -x 2'.split())
>>> args.func(args)
2.0
>>>
>>> # parse the args and call whatever function was selected
>>> args = parser.parse_args('bar XYZYX'.split())
>>> args.func(args)
((XYZYX))
This way, you can let :meth:`parse_args` do all the work for you, and then
just call the appropriate function after the argument parsing is complete.
Associating functions with actions like this is typically the easiest way
to handle the different actions for each of your subparsers. However, if you
find it necessary to check the name of the subparser that was invoked, you
can always provide a ``dest`` keyword argument to the :meth:`add_subparsers`
call::
>>> parser = argparse.ArgumentParser()
>>> subparsers = parser.add_subparsers(dest='subparser_name')
>>> subparser1 = subparsers.add_parser('1')
>>> subparser1.add_argument('-x')
>>> subparser2 = subparsers.add_parser('2')
>>> subparser2.add_argument('y')
>>> parser.parse_args(['2', 'frobble'])
Namespace(subparser_name='2', y='frobble')
FileType objects
^^^^^^^^^^^^^^^^
.. class:: FileType(mode='r', bufsize=None)
The :class:`FileType` factory creates objects that can be passed to the type
argument of :meth:`add_argument`. Arguments that have :class:`FileType`
objects as their type will open command-line args as files with the
requested modes and buffer sizes:
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--output', type=argparse.FileType('wb', 0))
>>> parser.parse_args(['--output', 'out'])
Namespace(output=<open file 'out', mode 'wb' at 0x...>)
FileType objects understand the pseudo-argument ``'-'`` and automatically
convert this into ``sys.stdin`` for readable :class:`FileType` objects and
``sys.stdout`` for writable :class:`FileType` objects:
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('infile', type=argparse.FileType('r'))
>>> parser.parse_args(['-'])
Namespace(infile=<open file '<stdin>', mode 'r' at 0x...>)
Argument groups
^^^^^^^^^^^^^^^
.. method:: add_argument_group([title], [description])
By default, ArgumentParser objects group command-line arguments into
"positional arguments" and "optional arguments" when displaying help
messages. When there is a better conceptual grouping of arguments than this
default one, appropriate groups can be created using the
:meth:`add_argument_group` method::
>>> parser = argparse.ArgumentParser(prog='PROG', add_help=False)
>>> group = parser.add_argument_group('group')
>>> group.add_argument('--foo', help='foo help')
>>> group.add_argument('bar', help='bar help')
>>> parser.print_help()
usage: PROG [--foo FOO] bar
group:
bar bar help
--foo FOO foo help
The :meth:`add_argument_group` method returns an argument group object which
has an :meth:`add_argument` method just like a regular ArgumentParser
objects. When an argument is added to the group, the parser treats it just
like a normal argument, but displays the argument in a separate group for
help messages. The :meth:`add_argument_group` method accepts ``title`` and
``description`` arguments which can be used to customize this display::
>>> parser = argparse.ArgumentParser(prog='PROG', add_help=False)
>>> group1 = parser.add_argument_group('group1', 'group1 description')
>>> group1.add_argument('foo', help='foo help')
>>> group2 = parser.add_argument_group('group2', 'group2 description')
>>> group2.add_argument('--bar', help='bar help')
>>> parser.print_help()
usage: PROG [--bar BAR] foo
group1:
group1 description
foo foo help
group2:
group2 description
--bar BAR bar help
Note that any arguments not in your user defined groups will end up back in
the usual "positional arguments" and "optional arguments" sections.
Mutual exclusion
^^^^^^^^^^^^^^^^
.. method:: add_mutually_exclusive_group([required=False])
Sometimes, you need to make sure that only one of a couple different options
is specified on the command line. You can create groups of such mutually
exclusive arguments using the :meth:`add_mutually_exclusive_group` method.
When :func:`parse_args` is called, argparse will make sure that only one of
the arguments in the mutually exclusive group was present on the command
line::
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> group = parser.add_mutually_exclusive_group()
>>> group.add_argument('--foo', action='store_true')
>>> group.add_argument('--bar', action='store_false')
>>> parser.parse_args(['--foo'])
Namespace(bar=True, foo=True)
>>> parser.parse_args(['--bar'])
Namespace(bar=False, foo=False)
>>> parser.parse_args(['--foo', '--bar'])
usage: PROG [-h] [--foo | --bar]
PROG: error: argument --bar: not allowed with argument --foo
The :meth:`add_mutually_exclusive_group` method also accepts a ``required``
argument, to indicate that at least one of the mutually exclusive arguments
is required::
>>> parser = argparse.ArgumentParser(prog='PROG')
>>> group = parser.add_mutually_exclusive_group(required=True)
>>> group.add_argument('--foo', action='store_true')
>>> group.add_argument('--bar', action='store_false')
>>> parser.parse_args([])
usage: PROG [-h] (--foo | --bar)
PROG: error: one of the arguments --foo --bar is required
Note that currently mutually exclusive argument groups do not support the
``title`` and ``description`` arguments of :meth:`add_argument_group`. This
may change in the future however, so you are *strongly* recommended to
specify ``required`` as a keyword argument if you use it.
Parser defaults
^^^^^^^^^^^^^^^
.. method:: set_defaults(**kwargs)
Most of the time, the attributes of the object returned by
:meth:`parse_args` will be fully determined by inspecting the command-line
args and the argument actions described in your :meth:`add_argument` calls.
However, sometimes it may be useful to add some additional attributes that
are determined without any inspection of the command-line. The
:meth:`set_defaults` method allows you to do this::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('foo', type=int)
>>> parser.set_defaults(bar=42, baz='badger')
>>> parser.parse_args(['736'])
Namespace(bar=42, baz='badger', foo=736)
Note that parser-level defaults always override argument-level defaults. So
if you set a parser-level default for a name that matches an argument, the
old argument default will no longer be used::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', default='bar')
>>> parser.set_defaults(foo='spam')
>>> parser.parse_args([])
Namespace(foo='spam')
Parser-level defaults can be particularly useful when you're working with
multiple parsers. See the :meth:`add_subparsers` method for an example of
this type.
.. method:: get_default(dest)
Get the default value for a namespace attribute, as set by either
:meth:`add_argument` or by :meth:`set_defaults`::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', default='badger')
>>> parser.get_default('foo')
'badger'
Printing help
^^^^^^^^^^^^^
In most typical applications, :meth:`parse_args` will take care of formatting
and printing any usage or error messages. However, should you want to format or
print these on your own, several methods are available:
.. method:: print_usage([file]):
Print a brief description of how the :class:`ArgumentParser` should be
invoked on the command line. If ``file`` is not present, ``sys.stderr`` is
assumed.
.. method:: print_help([file]):
Print a help message, including the program usage and information about the
arguments registered with the :class:`ArgumentParser`. If ``file`` is not
present, ``sys.stderr`` is assumed.
There are also variants of these methods that simply return a string instead of
printing it:
.. method:: format_usage():
Return a string containing a brief description of how the
:class:`ArgumentParser` should be invoked on the command line.
.. method:: format_help():
Return a string containing a help message, including the program usage and
information about the arguments registered with the :class:`ArgumentParser`.
Partial parsing
^^^^^^^^^^^^^^^
.. method:: parse_known_args([args], [namespace])
Sometimes a script may only parse a few of the command line arguments, passing
the remaining arguments on to another script or program. In these cases, the
:meth:`parse_known_args` method can be useful. It works much like
:meth:`parse_args` except that it does not produce an error when extra
arguments are present. Instead, it returns a two item tuple containing the
populated namespace and the list of remaining argument strings.
::
>>> parser = argparse.ArgumentParser()
>>> parser.add_argument('--foo', action='store_true')
>>> parser.add_argument('bar')
>>> parser.parse_known_args(['--foo', '--badger', 'BAR', 'spam'])
(Namespace(bar='BAR', foo=True), ['--badger', 'spam'])
Customizing file parsing
^^^^^^^^^^^^^^^^^^^^^^^^
.. method:: convert_arg_line_to_args(arg_line)
Arguments that are read from a file (see the ``fromfile_prefix_chars``
keyword argument to the :class:`ArgumentParser` constructor) are read one
argument per line. If you need fancier parsing, then you can subclass the
:class:`ArgumentParser` and override the :meth:`convert_arg_line_to_args`
method.
This method takes a single argument ``arg_line`` which is a string read from
the argument file. It returns a list of arguments parsed from this string.
The method is called once per line read from the argument file, in order.
A useful override of this method is one that treats each space-separated
word as an argument::
def convert_arg_line_to_args(self, arg_line):
for arg in arg_line.split():
if not arg.strip():
continue
yield arg
Upgrading optparse code
-----------------------
Originally, the argparse module had attempted to maintain compatibility with
optparse. However, optparse was difficult to extend transparently,
particularly with the changes required to support the new ``nargs=``
specifiers and better usage messges. When most everything in optparse had
either been copy-pasted over or monkey-patched, it no longer seemed practical
to try to maintain the backwards compatibility.
A partial upgrade path from optparse to argparse:
* Replace all ``add_option()`` calls with :meth:`add_argument` calls.
* Replace ``options, args = parser.parse_args()`` with
``args = parser.parse_args()`` and add additional :meth:`add_argument` calls
for the positional arguments.
* Replace callback actions and the ``callback_*`` keyword arguments with
``type`` or ``action`` arguments.
* Replace string names for ``type`` keyword arguments with the corresponding
type objects (e.g. int, float, complex, etc).
* Replace ``Values`` with ``Namespace`` and ``OptionError/OptionValueError``
with ``ArgumentError``.
* Replace strings with implicit arguments such as ``%default`` or ``%prog``
with the standard python syntax to use dictionaries to format strings, that
is, ``%(default)s`` and ``%(prog)s``.
Doc/library/getopt.rst
View file @ 6d265699
:mod:`getopt` --- Parser for command line options
=================================================
:mod:`getopt` --- C-style parser for command line options
=========================================================
.. module:: getopt
:synopsis: Portable parser for command line options; support both short and
......
Doc/library/optparse.rst
View file @ 6d265699
:mod:`optparse` --- More powerful command line option parser
============================================================
:mod:`optparse` --- Parser for command line options
===================================================
.. module:: optparse
:synopsis: More convenient, flexible, and powerful command-line parsing library.
:synopsis: Command-line option parsing library.
.. moduleauthor:: Greg Ward <gward@python.net>
.. sectionauthor:: Greg Ward <gward@python.net>
......
Doc/tutorial/stdlib.rst
View file @ 6d265699
......@@ -72,7 +72,7 @@ three`` at the command line::
The :mod:`getopt` module processes *sys.argv* using the conventions of the Unix
:func:`getopt` function. More powerful and flexible command line processing is
provided by the :mod:`optparse` module.
provided by the :mod:`argparse` module.
.. _tut-stderr:
......
Lib/argparse.py 0 → 100644
View file @ 6d265699
# -*- coding: utf-8 -*-
# Copyright © 2006-2009 Steven J. Bethard <steven.bethard@gmail.com>.
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may not
# use this file except in compliance with the License. You may obtain a copy
# of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
"""Command-line parsing library
This module is an optparse-inspired command-line parsing library that:
- handles both optional and positional arguments
- produces highly informative usage messages
- supports parsers that dispatch to sub-parsers
The following is a simple usage example that sums integers from the
command-line and writes the result to a file::
parser = argparse.ArgumentParser(
description='sum the integers at the command line')
parser.add_argument(
'integers', metavar='int', nargs='+', type=int,
help='an integer to be summed')
parser.add_argument(
'--log', default=sys.stdout, type=argparse.FileType('w'),
help='the file where the sum should be written')
args = parser.parse_args()
args.log.write('%s' % sum(args.integers))
args.log.close()
The module contains the following public classes:
- ArgumentParser -- The main entry point for command-line parsing. As the
example above shows, the add_argument() method is used to populate
the parser with actions for optional and positional arguments. Then
the parse_args() method is invoked to convert the args at the
command-line into an object with attributes.
- ArgumentError -- The exception raised by ArgumentParser objects when
there are errors with the parser's actions. Errors raised while
parsing the command-line are caught by ArgumentParser and emitted
as command-line messages.
- FileType -- A factory for defining types of files to be created. As the
example above shows, instances of FileType are typically passed as
the type= argument of add_argument() calls.
- Action -- The base class for parser actions. Typically actions are
selected by passing strings like 'store_true' or 'append_const' to
the action= argument of add_argument(). However, for greater
customization of ArgumentParser actions, subclasses of Action may
be defined and passed as the action= argument.
- HelpFormatter, RawDescriptionHelpFormatter, RawTextHelpFormatter,
ArgumentDefaultsHelpFormatter -- Formatter classes which
may be passed as the formatter_class= argument to the
ArgumentParser constructor. HelpFormatter is the default,
RawDescriptionHelpFormatter and RawTextHelpFormatter tell the parser
not to change the formatting for help text, and
ArgumentDefaultsHelpFormatter adds information about argument defaults
to the help.
All other classes in this module are considered implementation details.
(Also note that HelpFormatter and RawDescriptionHelpFormatter are only
considered public as object names -- the API of the formatter objects is
still considered an implementation detail.)
"""
__version__ = '1.1'
__all__ = [
'ArgumentParser',
'ArgumentError',
'Namespace',
'Action',
'FileType',
'HelpFormatter',
'RawDescriptionHelpFormatter',
'RawTextHelpFormatter',
'ArgumentDefaultsHelpFormatter',
]
import copy as _copy
import os as _os
import re as _re
import sys as _sys
import textwrap as _textwrap
from gettext import gettext as _
try:
_set = set
except NameError:
from sets import Set as _set
try:
_basestring = basestring
except NameError:
_basestring = str
try:
_sorted = sorted
except NameError:
def _sorted(iterable, reverse=False):
result = list(iterable)
result.sort()
if reverse:
result.reverse()
return result
def _callable(obj):
return hasattr(obj, '__call__') or hasattr(obj, '__bases__')
# silence Python 2.6 buggy warnings about Exception.message
if _sys.version_info[:2] == (2, 6):
import warnings
warnings.filterwarnings(
action='ignore',
message='BaseException.message has been deprecated as of Python 2.6',
category=DeprecationWarning,
module='argparse')
SUPPRESS = '==SUPPRESS=='
OPTIONAL = '?'
ZERO_OR_MORE = '*'
ONE_OR_MORE = '+'
PARSER = 'A...'
REMAINDER = '...'
# =============================
# Utility functions and classes
# =============================
class _AttributeHolder(object):
"""Abstract base class that provides __repr__.
The __repr__ method returns a string in the format::
ClassName(attr=name, attr=name, ...)
The attributes are determined either by a class-level attribute,
'_kwarg_names', or by inspecting the instance __dict__.
"""
def __repr__(self):
type_name = type(self).__name__
arg_strings = []
for arg in self._get_args():
arg_strings.append(repr(arg))
for name, value in self._get_kwargs():
arg_strings.append('%s=%r' % (name, value))
return '%s(%s)' % (type_name, ', '.join(arg_strings))
def _get_kwargs(self):
return _sorted(self.__dict__.items())
def _get_args(self):
return []
def _ensure_value(namespace, name, value):
if getattr(namespace, name, None) is None:
setattr(namespace, name, value)
return getattr(namespace, name)
# ===============
# Formatting Help
# ===============
class HelpFormatter(object):
"""Formatter for generating usage messages and argument help strings.
Only the name of this class is considered a public API. All the methods
provided by the class are considered an implementation detail.
"""
def __init__(self,
prog,
indent_increment=2,
max_help_position=24,
width=None):
# default setting for width
if width is None:
try:
width = int(_os.environ['COLUMNS'])
except (KeyError, ValueError):
width = 80
width -= 2
self._prog = prog
self._indent_increment = indent_increment
self._max_help_position = max_help_position
self._width = width
self._current_indent = 0
self._level = 0
self._action_max_length = 0
self._root_section = self._Section(self, None)
self._current_section = self._root_section
self._whitespace_matcher = _re.compile(r'\s+')
self._long_break_matcher = _re.compile(r'\n\n\n+')
# ===============================
# Section and indentation methods
# ===============================
def _indent(self):
self._current_indent += self._indent_increment
self._level += 1
def _dedent(self):
self._current_indent -= self._indent_increment
assert self._current_indent >= 0, 'Indent decreased below 0.'
self._level -= 1
class _Section(object):
def __init__(self, formatter, parent, heading=None):
self.formatter = formatter
self.parent = parent
self.heading = heading
self.items = []
def format_help(self):
# format the indented section
if self.parent is not None:
self.formatter._indent()
join = self.formatter._join_parts
for func, args in self.items:
func(*args)
item_help = join([func(*args) for func, args in self.items])
if self.parent is not None:
self.formatter._dedent()
# return nothing if the section was empty
if not item_help:
return ''
# add the heading if the section was non-empty
if self.heading is not SUPPRESS and self.heading is not None:
current_indent = self.formatter._current_indent
heading = '%*s%s:\n' % (current_indent, '', self.heading)
else:
heading = ''
# join the section-initial newline, the heading and the help
return join(['\n', heading, item_help, '\n'])
def _add_item(self, func, args):
self._current_section.items.append((func, args))
# ========================
# Message building methods
# ========================
def start_section(self, heading):
self._indent()
section = self._Section(self, self._current_section, heading)
self._add_item(section.format_help, [])
self._current_section = section
def end_section(self):
self._current_section = self._current_section.parent
self._dedent()
def add_text(self, text):
if text is not SUPPRESS and text is not None:
self._add_item(self._format_text, [text])
def add_usage(self, usage, actions, groups, prefix=None):
if usage is not SUPPRESS:
args = usage, actions, groups, prefix
self._add_item(self._format_usage, args)
def add_argument(self, action):
if action.help is not SUPPRESS:
# find all invocations
get_invocation = self._format_action_invocation
invocations = [get_invocation(action)]
for subaction in self._iter_indented_subactions(action):
invocations.append(get_invocation(subaction))
# update the maximum item length
invocation_length = max([len(s) for s in invocations])
action_length = invocation_length + self._current_indent
self._action_max_length = max(self._action_max_length,
action_length)
# add the item to the list
self._add_item(self._format_action, [action])
def add_arguments(self, actions):
for action in actions:
self.add_argument(action)
# =======================
# Help-formatting methods
# =======================
def format_help(self):
help = self._root_section.format_help()
if help:
help = self._long_break_matcher.sub('\n\n', help)
help = help.strip('\n') + '\n'
return help
def _join_parts(self, part_strings):
return ''.join([part
for part in part_strings
if part and part is not SUPPRESS])
def _format_usage(self, usage, actions, groups, prefix):
if prefix is None:
prefix = _('usage: ')
# if usage is specified, use that
if usage is not None:
usage = usage % dict(prog=self._prog)
# if no optionals or positionals are available, usage is just prog
elif usage is None and not actions:
usage = '%(prog)s' % dict(prog=self._prog)
# if optionals and positionals are available, calculate usage
elif usage is None:
prog = '%(prog)s' % dict(prog=self._prog)
# split optionals from positionals
optionals = []
positionals = []
for action in actions:
if action.option_strings:
optionals.append(action)
else:
positionals.append(action)
# build full usage string
format = self._format_actions_usage
action_usage = format(optionals + positionals, groups)
usage = ' '.join([s for s in [prog, action_usage] if s])
# wrap the usage parts if it's too long
text_width = self._width - self._current_indent
if len(prefix) + len(usage) > text_width:
# break usage into wrappable parts
part_regexp = r'\(.*?\)+|\[.*?\]+|\S+'
opt_usage = format(optionals, groups)
pos_usage = format(positionals, groups)
opt_parts = _re.findall(part_regexp, opt_usage)
pos_parts = _re.findall(part_regexp, pos_usage)
assert ' '.join(opt_parts) == opt_usage
assert ' '.join(pos_parts) == pos_usage
# helper for wrapping lines
def get_lines(parts, indent, prefix=None):
lines = []
line = []
if prefix is not None:
line_len = len(prefix) - 1
else:
line_len = len(indent) - 1
for part in parts:
if line_len + 1 + len(part) > text_width:
lines.append(indent + ' '.join(line))
line = []
line_len = len(indent) - 1
line.append(part)
line_len += len(part) + 1
if line:
lines.append(indent + ' '.join(line))
if prefix is not None:
lines[0] = lines[0][len(indent):]
return lines
# if prog is short, follow it with optionals or positionals
if len(prefix) + len(prog) <= 0.75 * text_width:
indent = ' ' * (len(prefix) + len(prog) + 1)
if opt_parts:
lines = get_lines([prog] + opt_parts, indent, prefix)
lines.extend(get_lines(pos_parts, indent))
elif pos_parts:
lines = get_lines([prog] + pos_parts, indent, prefix)
else:
lines = [prog]
# if prog is long, put it on its own line
else:
indent = ' ' * len(prefix)
parts = opt_parts + pos_parts
lines = get_lines(parts, indent)
if len(lines) > 1:
lines = []
lines.extend(get_lines(opt_parts, indent))
lines.extend(get_lines(pos_parts, indent))
lines = [prog] + lines
# join lines into usage
usage = '\n'.join(lines)
# prefix with 'usage:'
return '%s%s\n\n' % (prefix, usage)
def _format_actions_usage(self, actions, groups):
# find group indices and identify actions in groups
group_actions = _set()
inserts = {}
for group in groups:
try:
start = actions.index(group._group_actions[0])
except ValueError:
continue
else:
end = start + len(group._group_actions)
if actions[start:end] == group._group_actions:
for action in group._group_actions:
group_actions.add(action)
if not group.required:
inserts[start] = '['
inserts[end] = ']'
else:
inserts[start] = '('
inserts[end] = ')'
for i in range(start + 1, end):
inserts[i] = '|'
# collect all actions format strings
parts = []
for i, action in enumerate(actions):
# suppressed arguments are marked with None
# remove | separators for suppressed arguments
if action.help is SUPPRESS:
parts.append(None)
if inserts.get(i) == '|':
inserts.pop(i)
elif inserts.get(i + 1) == '|':
inserts.pop(i + 1)
# produce all arg strings
elif not action.option_strings:
part = self._format_args(action, action.dest)
# if it's in a group, strip the outer []
if action in group_actions:
if part[0] == '[' and part[-1] == ']':
part = part[1:-1]
# add the action string to the list
parts.append(part)
# produce the first way to invoke the option in brackets
else:
option_string = action.option_strings[0]
# if the Optional doesn't take a value, format is:
# -s or --long
if action.nargs == 0:
part = '%s' % option_string
# if the Optional takes a value, format is:
# -s ARGS or --long ARGS
else:
default = action.dest.upper()
args_string = self._format_args(action, default)
part = '%s %s' % (option_string, args_string)
# make it look optional if it's not required or in a group
if not action.required and action not in group_actions:
part = '[%s]' % part
# add the action string to the list
parts.append(part)
# insert things at the necessary indices
for i in _sorted(inserts, reverse=True):
parts[i:i] = [inserts[i]]
# join all the action items with spaces
text = ' '.join([item for item in parts if item is not None])
# clean up separators for mutually exclusive groups
open = r'[\[(]'
close = r'[\])]'
text = _re.sub(r'(%s) ' % open, r'\1', text)
text = _re.sub(r' (%s)' % close, r'\1', text)
text = _re.sub(r'%s *%s' % (open, close), r'', text)
text = _re.sub(r'\(([^|]*)\)', r'\1', text)
text = text.strip()
# return the text
return text
def _format_text(self, text):
if '%(prog)' in text:
text = text % dict(prog=self._prog)
text_width = self._width - self._current_indent
indent = ' ' * self._current_indent
return self._fill_text(text, text_width, indent) + '\n\n'
def _format_action(self, action):
# determine the required width and the entry label
help_position = min(self._action_max_length + 2,
self._max_help_position)
help_width = self._width - help_position
action_width = help_position - self._current_indent - 2
action_header = self._format_action_invocation(action)
# ho nelp; start on same line and add a final newline
if not action.help:
tup = self._current_indent, '', action_header
action_header = '%*s%s\n' % tup
# short action name; start on the same line and pad two spaces
elif len(action_header) <= action_width:
tup = self._current_indent, '', action_width, action_header
action_header = '%*s%-*s ' % tup
indent_first = 0
# long action name; start on the next line
else:
tup = self._current_indent, '', action_header
action_header = '%*s%s\n' % tup
indent_first = help_position
# collect the pieces of the action help
parts = [action_header]
# if there was help for the action, add lines of help text
if action.help:
help_text = self._expand_help(action)
help_lines = self._split_lines(help_text, help_width)
parts.append('%*s%s\n' % (indent_first, '', help_lines[0]))
for line in help_lines[1:]:
parts.append('%*s%s\n' % (help_position, '', line))
# or add a newline if the description doesn't end with one
elif not action_header.endswith('\n'):
parts.append('\n')
# if there are any sub-actions, add their help as well
for subaction in self._iter_indented_subactions(action):
parts.append(self._format_action(subaction))
# return a single string
return self._join_parts(parts)
def _format_action_invocation(self, action):
if not action.option_strings:
metavar, = self._metavar_formatter(action, action.dest)(1)
return metavar
else:
parts = []
# if the Optional doesn't take a value, format is:
# -s, --long
if action.nargs == 0:
parts.extend(action.option_strings)
# if the Optional takes a value, format is:
# -s ARGS, --long ARGS
else:
default = action.dest.upper()
args_string = self._format_args(action, default)
for option_string in action.option_strings:
parts.append('%s %s' % (option_string, args_string))
return ', '.join(parts)
def _metavar_formatter(self, action, default_metavar):
if action.metavar is not None:
result = action.metavar
elif action.choices is not None:
choice_strs = [str(choice) for choice in action.choices]
result = '{%s}' % ','.join(choice_strs)
else:
result = default_metavar
def format(tuple_size):
if isinstance(result, tuple):
return result
else:
return (result, ) * tuple_size
return format
def _format_args(self, action, default_metavar):
get_metavar = self._metavar_formatter(action, default_metavar)
if action.nargs is None:
result = '%s' % get_metavar(1)
elif action.nargs == OPTIONAL:
result = '[%s]' % get_metavar(1)
elif action.nargs == ZERO_OR_MORE:
result = '[%s [%s ...]]' % get_metavar(2)
elif action.nargs == ONE_OR_MORE:
result = '%s [%s ...]' % get_metavar(2)
elif action.nargs == REMAINDER:
result = '...'
elif action.nargs == PARSER:
result = '%s ...' % get_metavar(1)
else:
formats = ['%s' for _ in range(action.nargs)]
result = ' '.join(formats) % get_metavar(action.nargs)
return result
def _expand_help(self, action):
params = dict(vars(action), prog=self._prog)
for name in list(params):
if params[name] is SUPPRESS:
del params[name]
for name in list(params):
if hasattr(params[name], '__name__'):
params[name] = params[name].__name__
if params.get('choices') is not None:
choices_str = ', '.join([str(c) for c in params['choices']])
params['choices'] = choices_str
return self._get_help_string(action) % params
def _iter_indented_subactions(self, action):
try:
get_subactions = action._get_subactions
except AttributeError:
pass
else:
self._indent()
for subaction in get_subactions():
yield subaction
self._dedent()
def _split_lines(self, text, width):
text = self._whitespace_matcher.sub(' ', text).strip()
return _textwrap.wrap(text, width)
def _fill_text(self, text, width, indent):
text = self._whitespace_matcher.sub(' ', text).strip()
return _textwrap.fill(text, width, initial_indent=indent,
subsequent_indent=indent)
def _get_help_string(self, action):
return action.help
class RawDescriptionHelpFormatter(HelpFormatter):
"""Help message formatter which retains any formatting in descriptions.
Only the name of this class is considered a public API. All the methods
provided by the class are considered an implementation detail.
"""
def _fill_text(self, text, width, indent):
return ''.join([indent + line for line in text.splitlines(True)])
class RawTextHelpFormatter(RawDescriptionHelpFormatter):
"""Help message formatter which retains formatting of all help text.
Only the name of this class is considered a public API. All the methods
provided by the class are considered an implementation detail.
"""
def _split_lines(self, text, width):
return text.splitlines()
class ArgumentDefaultsHelpFormatter(HelpFormatter):
"""Help message formatter which adds default values to argument help.
Only the name of this class is considered a public API. All the methods
provided by the class are considered an implementation detail.
"""
def _get_help_string(self, action):
help = action.help
if '%(default)' not in action.help:
if action.default is not SUPPRESS:
defaulting_nargs = [OPTIONAL, ZERO_OR_MORE]
if action.option_strings or action.nargs in defaulting_nargs:
help += ' (default: %(default)s)'
return help
# =====================
# Options and Arguments
# =====================
def _get_action_name(argument):
if argument is None:
return None
elif argument.option_strings:
return '/'.join(argument.option_strings)
elif argument.metavar not in (None, SUPPRESS):
return argument.metavar
elif argument.dest not in (None, SUPPRESS):
return argument.dest
else:
return None
class ArgumentError(Exception):
"""An error from creating or using an argument (optional or positional).
The string value of this exception is the message, augmented with
information about the argument that caused it.
"""
def __init__(self, argument, message):
self.argument_name = _get_action_name(argument)
self.message = message
def __str__(self):
if self.argument_name is None:
format = '%(message)s'
else:
format = 'argument %(argument_name)s: %(message)s'
return format % dict(message=self.message,
argument_name=self.argument_name)
class ArgumentTypeError(Exception):
"""An error from trying to convert a command line string to a type."""
pass
# ==============
# Action classes
# ==============
class Action(_AttributeHolder):
"""Information about how to convert command line strings to Python objects.
Action objects are used by an ArgumentParser to represent the information
needed to parse a single argument from one or more strings from the
command line. The keyword arguments to the Action constructor are also
all attributes of Action instances.
Keyword Arguments:
- option_strings -- A list of command-line option strings which
should be associated with this action.
- dest -- The name of the attribute to hold the created object(s)
- nargs -- The number of command-line arguments that should be
consumed. By default, one argument will be consumed and a single
value will be produced. Other values include:
- N (an integer) consumes N arguments (and produces a list)
- '?' consumes zero or one arguments
- '*' consumes zero or more arguments (and produces a list)
- '+' consumes one or more arguments (and produces a list)
Note that the difference between the default and nargs=1 is that
with the default, a single value will be produced, while with
nargs=1, a list containing a single value will be produced.
- const -- The value to be produced if the option is specified and the
option uses an action that takes no values.
- default -- The value to be produced if the option is not specified.
- type -- The type which the command-line arguments should be converted
to, should be one of 'string', 'int', 'float', 'complex' or a
callable object that accepts a single string argument. If None,
'string' is assumed.
- choices -- A container of values that should be allowed. If not None,
after a command-line argument has been converted to the appropriate
type, an exception will be raised if it is not a member of this
collection.
- required -- True if the action must always be specified at the
command line. This is only meaningful for optional command-line
arguments.
- help -- The help string describing the argument.
- metavar -- The name to be used for the option's argument with the
help string. If None, the 'dest' value will be used as the name.
"""
def __init__(self,
option_strings,
dest,
nargs=None,
const=None,
default=None,
type=None,
choices=None,
required=False,
help=None,
metavar=None):
self.option_strings = option_strings
self.dest = dest
self.nargs = nargs
self.const = const
self.default = default
self.type = type
self.choices = choices
self.required = required
self.help = help
self.metavar = metavar
def _get_kwargs(self):
names = [
'option_strings',
'dest',
'nargs',
'const',
'default',
'type',
'choices',
'help',
'metavar',
]
return [(name, getattr(self, name)) for name in names]
def __call__(self, parser, namespace, values, option_string=None):
raise NotImplementedError(_('.__call__() not defined'))
class _StoreAction(Action):
def __init__(self,
option_strings,
dest,
nargs=None,
const=None,
default=None,
type=None,
choices=None,
required=False,
help=None,
metavar=None):
if nargs == 0:
raise ValueError('nargs for store actions must be > 0; if you '
'have nothing to store, actions such as store '
'true or store const may be more appropriate')
if const is not None and nargs != OPTIONAL:
raise ValueError('nargs must be %r to supply const' % OPTIONAL)
super(_StoreAction, self).__init__(
option_strings=option_strings,
dest=dest,
nargs=nargs,
const=const,
default=default,
type=type,
choices=choices,
required=required,
help=help,
metavar=metavar)
def __call__(self, parser, namespace, values, option_string=None):
setattr(namespace, self.dest, values)
class _StoreConstAction(Action):
def __init__(self,
option_strings,
dest,
const,
default=None,
required=False,
help=None,
metavar=None):
super(_StoreConstAction, self).__init__(
option_strings=option_strings,
dest=dest,
nargs=0,
const=const,
default=default,
required=required,
help=help)
def __call__(self, parser, namespace, values, option_string=None):
setattr(namespace, self.dest, self.const)
class _StoreTrueAction(_StoreConstAction):
def __init__(self,
option_strings,
dest,
default=False,
required=False,
help=None):
super(_StoreTrueAction, self).__init__(
option_strings=option_strings,
dest=dest,
const=True,
default=default,
required=required,
help=help)
class _StoreFalseAction(_StoreConstAction):
def __init__(self,
option_strings,
dest,
default=True,
required=False,
help=None):
super(_StoreFalseAction, self).__init__(
option_strings=option_strings,
dest=dest,
const=False,
default=default,
required=required,
help=help)
class _AppendAction(Action):
def __init__(self,
option_strings,
dest,
nargs=None,
const=None,
default=None,
type=None,
choices=None,
required=False,
help=None,
metavar=None):
if nargs == 0:
raise ValueError('nargs for append actions must be > 0; if arg '
'strings are not supplying the value to append, '
'the append const action may be more appropriate')
if const is not None and nargs != OPTIONAL:
raise ValueError('nargs must be %r to supply const' % OPTIONAL)
super(_AppendAction, self).__init__(
option_strings=option_strings,
dest=dest,
nargs=nargs,
const=const,
default=default,
type=type,
choices=choices,
required=required,
help=help,
metavar=metavar)
def __call__(self, parser, namespace, values, option_string=None):
items = _copy.copy(_ensure_value(namespace, self.dest, []))
items.append(values)
setattr(namespace, self.dest, items)
class _AppendConstAction(Action):
def __init__(self,
option_strings,
dest,
const,
default=None,
required=False,
help=None,
metavar=None):
super(_AppendConstAction, self).__init__(
option_strings=option_strings,
dest=dest,
nargs=0,
const=const,
default=default,
required=required,
help=help,
metavar=metavar)
def __call__(self, parser, namespace, values, option_string=None):
items = _copy.copy(_ensure_value(namespace, self.dest, []))
items.append(self.const)
setattr(namespace, self.dest, items)
class _CountAction(Action):
def __init__(self,
option_strings,
dest,
default=None,
required=False,
help=None):
super(_CountAction, self).__init__(
option_strings=option_strings,
dest=dest,
nargs=0,
default=default,
required=required,
help=help)
def __call__(self, parser, namespace, values, option_string=None):
new_count = _ensure_value(namespace, self.dest, 0) + 1
setattr(namespace, self.dest, new_count)
class _HelpAction(Action):
def __init__(self,
option_strings,
dest=SUPPRESS,
default=SUPPRESS,
help=None):
super(_HelpAction, self).__init__(
option_strings=option_strings,
dest=dest,
default=default,
nargs=0,
help=help)
def __call__(self, parser, namespace, values, option_string=None):
parser.print_help()
parser.exit()
class _VersionAction(Action):
def __init__(self,
option_strings,
version=None,
dest=SUPPRESS,
default=SUPPRESS,
help=None):
super(_VersionAction, self).__init__(
option_strings=option_strings,
dest=dest,
default=default,
nargs=0,
help=help)
self.version = version
def __call__(self, parser, namespace, values, option_string=None):
version = self.version
if version is None:
version = parser.version
formatter = parser._get_formatter()
formatter.add_text(version)
parser.exit(message=formatter.format_help())
class _SubParsersAction(Action):
class _ChoicesPseudoAction(Action):
def __init__(self, name, help):
sup = super(_SubParsersAction._ChoicesPseudoAction, self)
sup.__init__(option_strings=[], dest=name, help=help)
def __init__(self,
option_strings,
prog,
parser_class,
dest=SUPPRESS,
help=None,
metavar=None):
self._prog_prefix = prog
self._parser_class = parser_class
self._name_parser_map = {}
self._choices_actions = []
super(_SubParsersAction, self).__init__(
option_strings=option_strings,
dest=dest,
nargs=PARSER,
choices=self._name_parser_map,
help=help,
metavar=metavar)
def add_parser(self, name, **kwargs):
# set prog from the existing prefix
if kwargs.get('prog') is None:
kwargs['prog'] = '%s %s' % (self._prog_prefix, name)
# create a pseudo-action to hold the choice help
if 'help' in kwargs:
help = kwargs.pop('help')
choice_action = self._ChoicesPseudoAction(name, help)
self._choices_actions.append(choice_action)
# create the parser and add it to the map
parser = self._parser_class(**kwargs)
self._name_parser_map[name] = parser
return parser
def _get_subactions(self):
return self._choices_actions
def __call__(self, parser, namespace, values, option_string=None):
parser_name = values[0]
arg_strings = values[1:]
# set the parser name if requested
if self.dest is not SUPPRESS:
setattr(namespace, self.dest, parser_name)
# select the parser
try:
parser = self._name_parser_map[parser_name]
except KeyError:
tup = parser_name, ', '.join(self._name_parser_map)
msg = _('unknown parser %r (choices: %s)' % tup)
raise ArgumentError(self, msg)
# parse all the remaining options into the namespace
parser.parse_args(arg_strings, namespace)
# ==============
# Type classes
# ==============
class FileType(object):
"""Factory for creating file object types
Instances of FileType are typically passed as type= arguments to the
ArgumentParser add_argument() method.
Keyword Arguments:
- mode -- A string indicating how the file is to be opened. Accepts the
same values as the builtin open() function.
- bufsize -- The file's desired buffer size. Accepts the same values as
the builtin open() function.
"""
def __init__(self, mode='r', bufsize=None):
self._mode = mode
self._bufsize = bufsize
def __call__(self, string):
# the special argument "-" means sys.std{in,out}
if string == '-':
if 'r' in self._mode:
return _sys.stdin
elif 'w' in self._mode:
return _sys.stdout
else:
msg = _('argument "-" with mode %r' % self._mode)
raise ValueError(msg)
# all other arguments are used as file names
if self._bufsize:
return open(string, self._mode, self._bufsize)
else:
return open(string, self._mode)
def __repr__(self):
args = [self._mode, self._bufsize]
args_str = ', '.join([repr(arg) for arg in args if arg is not None])
return '%s(%s)' % (type(self).__name__, args_str)
# ===========================
# Optional and Positional Parsing
# ===========================
class Namespace(_AttributeHolder):
"""Simple object for storing attributes.
Implements equality by attribute names and values, and provides a simple
string representation.
"""
def __init__(self, **kwargs):
for name in kwargs:
setattr(self, name, kwargs[name])
def __eq__(self, other):
return vars(self) == vars(other)
def __ne__(self, other):
return not (self == other)
def __contains__(self, key):
return key in self.__dict__
class _ActionsContainer(object):
def __init__(self,
description,
prefix_chars,
argument_default,
conflict_handler):
super(_ActionsContainer, self).__init__()
self.description = description
self.argument_default = argument_default
self.prefix_chars = prefix_chars
self.conflict_handler = conflict_handler
# set up registries
self._registries = {}
# register actions
self.register('action', None, _StoreAction)
self.register('action', 'store', _StoreAction)
self.register('action', 'store_const', _StoreConstAction)
self.register('action', 'store_true', _StoreTrueAction)
self.register('action', 'store_false', _StoreFalseAction)
self.register('action', 'append', _AppendAction)
self.register('action', 'append_const', _AppendConstAction)
self.register('action', 'count', _CountAction)
self.register('action', 'help', _HelpAction)
self.register('action', 'version', _VersionAction)
self.register('action', 'parsers', _SubParsersAction)
# raise an exception if the conflict handler is invalid
self._get_handler()
# action storage
self._actions = []
self._option_string_actions = {}
# groups
self._action_groups = []
self._mutually_exclusive_groups = []
# defaults storage
self._defaults = {}
# determines whether an "option" looks like a negative number
self._negative_number_matcher = _re.compile(r'^-\d+$|^-\d*\.\d+$')
# whether or not there are any optionals that look like negative
# numbers -- uses a list so it can be shared and edited
self._has_negative_number_optionals = []
# ====================
# Registration methods
# ====================
def register(self, registry_name, value, object):
registry = self._registries.setdefault(registry_name, {})
registry[value] = object
def _registry_get(self, registry_name, value, default=None):
return self._registries[registry_name].get(value, default)
# ==================================
# Namespace default accessor methods
# ==================================
def set_defaults(self, **kwargs):
self._defaults.update(kwargs)
# if these defaults match any existing arguments, replace
# the previous default on the object with the new one
for action in self._actions:
if action.dest in kwargs:
action.default = kwargs[action.dest]
def get_default(self, dest):
for action in self._actions:
if action.dest == dest and action.default is not None:
return action.default
return self._defaults.get(dest, None)
# =======================
# Adding argument actions
# =======================
def add_argument(self, *args, **kwargs):
"""
add_argument(dest, ..., name=value, ...)
add_argument(option_string, option_string, ..., name=value, ...)
"""
# if no positional args are supplied or only one is supplied and
# it doesn't look like an option string, parse a positional
# argument
chars = self.prefix_chars
if not args or len(args) == 1 and args[0][0] not in chars:
if args and 'dest' in kwargs:
raise ValueError('dest supplied twice for positional argument')
kwargs = self._get_positional_kwargs(*args, **kwargs)
# otherwise, we're adding an optional argument
else:
kwargs = self._get_optional_kwargs(*args, **kwargs)
# if no default was supplied, use the parser-level default
if 'default' not in kwargs:
dest = kwargs['dest']
if dest in self._defaults:
kwargs['default'] = self._defaults[dest]
elif self.argument_default is not None:
kwargs['default'] = self.argument_default
# create the action object, and add it to the parser
action_class = self._pop_action_class(kwargs)
if not _callable(action_class):
raise ValueError('unknown action "%s"' % action_class)
action = action_class(**kwargs)
# raise an error if the action type is not callable
type_func = self._registry_get('type', action.type, action.type)
if not _callable(type_func):
raise ValueError('%r is not callable' % type_func)
return self._add_action(action)
def add_argument_group(self, *args, **kwargs):
group = _ArgumentGroup(self, *args, **kwargs)
self._action_groups.append(group)
return group
def add_mutually_exclusive_group(self, **kwargs):
group = _MutuallyExclusiveGroup(self, **kwargs)
self._mutually_exclusive_groups.append(group)
return group
def _add_action(self, action):
# resolve any conflicts
self._check_conflict(action)
# add to actions list
self._actions.append(action)
action.container = self
# index the action by any option strings it has
for option_string in action.option_strings:
self._option_string_actions[option_string] = action
# set the flag if any option strings look like negative numbers
for option_string in action.option_strings:
if self._negative_number_matcher.match(option_string):
if not self._has_negative_number_optionals:
self._has_negative_number_optionals.append(True)
# return the created action
return action
def _remove_action(self, action):
self._actions.remove(action)
def _add_container_actions(self, container):
# collect groups by titles
title_group_map = {}
for group in self._action_groups:
if group.title in title_group_map:
msg = _('cannot merge actions - two groups are named %r')
raise ValueError(msg % (group.title))
title_group_map[group.title] = group
# map each action to its group
group_map = {}
for group in container._action_groups:
# if a group with the title exists, use that, otherwise
# create a new group matching the container's group
if group.title not in title_group_map:
title_group_map[group.title] = self.add_argument_group(
title=group.title,
description=group.description,
conflict_handler=group.conflict_handler)
# map the actions to their new group
for action in group._group_actions:
group_map[action] = title_group_map[group.title]
# add container's mutually exclusive groups
# NOTE: if add_mutually_exclusive_group ever gains title= and
# description= then this code will need to be expanded as above
for group in container._mutually_exclusive_groups:
mutex_group = self.add_mutually_exclusive_group(
required=group.required)
# map the actions to their new mutex group
for action in group._group_actions:
group_map[action] = mutex_group
# add all actions to this container or their group
for action in container._actions:
group_map.get(action, self)._add_action(action)
def _get_positional_kwargs(self, dest, **kwargs):
# make sure required is not specified
if 'required' in kwargs:
msg = _("'required' is an invalid argument for positionals")
raise TypeError(msg)
# mark positional arguments as required if at least one is
# always required
if kwargs.get('nargs') not in [OPTIONAL, ZERO_OR_MORE]:
kwargs['required'] = True
if kwargs.get('nargs') == ZERO_OR_MORE and 'default' not in kwargs:
kwargs['required'] = True
# return the keyword arguments with no option strings
return dict(kwargs, dest=dest, option_strings=[])
def _get_optional_kwargs(self, *args, **kwargs):
# determine short and long option strings
option_strings = []
long_option_strings = []
for option_string in args:
# error on strings that don't start with an appropriate prefix
if not option_string[0] in self.prefix_chars:
msg = _('invalid option string %r: '
'must start with a character %r')
tup = option_string, self.prefix_chars
raise ValueError(msg % tup)
# strings starting with two prefix characters are long options
option_strings.append(option_string)
if option_string[0] in self.prefix_chars:
if len(option_string) > 1:
if option_string[1] in self.prefix_chars:
long_option_strings.append(option_string)
# infer destination, '--foo-bar' -> 'foo_bar' and '-x' -> 'x'
dest = kwargs.pop('dest', None)
if dest is None:
if long_option_strings:
dest_option_string = long_option_strings[0]
else:
dest_option_string = option_strings[0]
dest = dest_option_string.lstrip(self.prefix_chars)
if not dest:
msg = _('dest= is required for options like %r')
raise ValueError(msg % option_string)
dest = dest.replace('-', '_')
# return the updated keyword arguments
return dict(kwargs, dest=dest, option_strings=option_strings)
def _pop_action_class(self, kwargs, default=None):
action = kwargs.pop('action', default)
return self._registry_get('action', action, action)
def _get_handler(self):
# determine function from conflict handler string
handler_func_name = '_handle_conflict_%s' % self.conflict_handler
try:
return getattr(self, handler_func_name)
except AttributeError:
msg = _('invalid conflict_resolution value: %r')
raise ValueError(msg % self.conflict_handler)
def _check_conflict(self, action):
# find all options that conflict with this option
confl_optionals = []
for option_string in action.option_strings:
if option_string in self._option_string_actions:
confl_optional = self._option_string_actions[option_string]
confl_optionals.append((option_string, confl_optional))
# resolve any conflicts
if confl_optionals:
conflict_handler = self._get_handler()
conflict_handler(action, confl_optionals)
def _handle_conflict_error(self, action, conflicting_actions):
message = _('conflicting option string(s): %s')
conflict_string = ', '.join([option_string
for option_string, action
in conflicting_actions])
raise ArgumentError(action, message % conflict_string)
def _handle_conflict_resolve(self, action, conflicting_actions):
# remove all conflicting options
for option_string, action in conflicting_actions:
# remove the conflicting option
action.option_strings.remove(option_string)
self._option_string_actions.pop(option_string, None)
# if the option now has no option string, remove it from the
# container holding it
if not action.option_strings:
action.container._remove_action(action)
class _ArgumentGroup(_ActionsContainer):
def __init__(self, container, title=None, description=None, **kwargs):
# add any missing keyword arguments by checking the container
update = kwargs.setdefault
update('conflict_handler', container.conflict_handler)
update('prefix_chars', container.prefix_chars)
update('argument_default', container.argument_default)
super_init = super(_ArgumentGroup, self).__init__
super_init(description=description, **kwargs)
# group attributes
self.title = title
self._group_actions = []
# share most attributes with the container
self._registries = container._registries
self._actions = container._actions
self._option_string_actions = container._option_string_actions
self._defaults = container._defaults
self._has_negative_number_optionals = \
container._has_negative_number_optionals
def _add_action(self, action):
action = super(_ArgumentGroup, self)._add_action(action)
self._group_actions.append(action)
return action
def _remove_action(self, action):
super(_ArgumentGroup, self)._remove_action(action)
self._group_actions.remove(action)
class _MutuallyExclusiveGroup(_ArgumentGroup):
def __init__(self, container, required=False):
super(_MutuallyExclusiveGroup, self).__init__(container)
self.required = required
self._container = container
def _add_action(self, action):
if action.required:
msg = _('mutually exclusive arguments must be optional')
raise ValueError(msg)
action = self._container._add_action(action)
self._group_actions.append(action)
return action
def _remove_action(self, action):
self._container._remove_action(action)
self._group_actions.remove(action)
class ArgumentParser(_AttributeHolder, _ActionsContainer):
"""Object for parsing command line strings into Python objects.
Keyword Arguments:
- prog -- The name of the program (default: sys.argv[0])
- usage -- A usage message (default: auto-generated from arguments)
- description -- A description of what the program does
- epilog -- Text following the argument descriptions
- parents -- Parsers whose arguments should be copied into this one
- formatter_class -- HelpFormatter class for printing help messages
- prefix_chars -- Characters that prefix optional arguments
- fromfile_prefix_chars -- Characters that prefix files containing
additional arguments
- argument_default -- The default value for all arguments
- conflict_handler -- String indicating how to handle conflicts
- add_help -- Add a -h/-help option
"""
def __init__(self,
prog=None,
usage=None,
description=None,
epilog=None,
version=None,
parents=[],
formatter_class=HelpFormatter,
prefix_chars='-',
fromfile_prefix_chars=None,
argument_default=None,
conflict_handler='error',
add_help=True):
if version is not None:
import warnings
warnings.warn(
"""The "version" argument to ArgumentParser is deprecated. """
"""Please use """
""""add_argument(..., action='version', version="N", ...)" """
"""instead""", DeprecationWarning)
superinit = super(ArgumentParser, self).__init__
superinit(description=description,
prefix_chars=prefix_chars,
argument_default=argument_default,
conflict_handler=conflict_handler)
# default setting for prog
if prog is None:
prog = _os.path.basename(_sys.argv[0])
self.prog = prog
self.usage = usage
self.epilog = epilog
self.version = version
self.formatter_class = formatter_class
self.fromfile_prefix_chars = fromfile_prefix_chars
self.add_help = add_help
add_group = self.add_argument_group
self._positionals = add_group(_('positional arguments'))
self._optionals = add_group(_('optional arguments'))
self._subparsers = None
# register types
def identity(string):
return string
self.register('type', None, identity)
# add help and version arguments if necessary
# (using explicit default to override global argument_default)
if self.add_help:
self.add_argument(
'-h', '--help', action='help', default=SUPPRESS,
help=_('show this help message and exit'))
if self.version:
self.add_argument(
'-v', '--version', action='version', default=SUPPRESS,
version=self.version,
help=_("show program's version number and exit"))
# add parent arguments and defaults
for parent in parents:
self._add_container_actions(parent)
try:
defaults = parent._defaults
except AttributeError:
pass
else:
self._defaults.update(defaults)
# =======================
# Pretty __repr__ methods
# =======================
def _get_kwargs(self):
names = [
'prog',
'usage',
'description',
'version',
'formatter_class',
'conflict_handler',
'add_help',
]
return [(name, getattr(self, name)) for name in names]
# ==================================
# Optional/Positional adding methods
# ==================================
def add_subparsers(self, **kwargs):
if self._subparsers is not None:
self.error(_('cannot have multiple subparser arguments'))
# add the parser class to the arguments if it's not present
kwargs.setdefault('parser_class', type(self))
if 'title' in kwargs or 'description' in kwargs:
title = _(kwargs.pop('title', 'subcommands'))
description = _(kwargs.pop('description', None))
self._subparsers = self.add_argument_group(title, description)
else:
self._subparsers = self._positionals
# prog defaults to the usage message of this parser, skipping
# optional arguments and with no "usage:" prefix
if kwargs.get('prog') is None:
formatter = self._get_formatter()
positionals = self._get_positional_actions()
groups = self._mutually_exclusive_groups
formatter.add_usage(self.usage, positionals, groups, '')
kwargs['prog'] = formatter.format_help().strip()
# create the parsers action and add it to the positionals list
parsers_class = self._pop_action_class(kwargs, 'parsers')
action = parsers_class(option_strings=[], **kwargs)
self._subparsers._add_action(action)
# return the created parsers action
return action
def _add_action(self, action):
if action.option_strings:
self._optionals._add_action(action)
else:
self._positionals._add_action(action)
return action
def _get_optional_actions(self):
return [action
for action in self._actions
if action.option_strings]
def _get_positional_actions(self):
return [action
for action in self._actions
if not action.option_strings]
# =====================================
# Command line argument parsing methods
# =====================================
def parse_args(self, args=None, namespace=None):
args, argv = self.parse_known_args(args, namespace)
if argv:
msg = _('unrecognized arguments: %s')
self.error(msg % ' '.join(argv))
return args
def parse_known_args(self, args=None, namespace=None):
# args default to the system args
if args is None:
args = _sys.argv[1:]
# default Namespace built from parser defaults
if namespace is None:
namespace = Namespace()
# add any action defaults that aren't present
for action in self._actions:
if action.dest is not SUPPRESS:
if not hasattr(namespace, action.dest):
if action.default is not SUPPRESS:
default = action.default
if isinstance(action.default, _basestring):
default = self._get_value(action, default)
setattr(namespace, action.dest, default)
# add any parser defaults that aren't present
for dest in self._defaults:
if not hasattr(namespace, dest):
setattr(namespace, dest, self._defaults[dest])
# parse the arguments and exit if there are any errors
try:
return self._parse_known_args(args, namespace)
except ArgumentError:
err = _sys.exc_info()[1]
self.error(str(err))
def _parse_known_args(self, arg_strings, namespace):
# replace arg strings that are file references
if self.fromfile_prefix_chars is not None:
arg_strings = self._read_args_from_files(arg_strings)
# map all mutually exclusive arguments to the other arguments
# they can't occur with
action_conflicts = {}
for mutex_group in self._mutually_exclusive_groups:
group_actions = mutex_group._group_actions
for i, mutex_action in enumerate(mutex_group._group_actions):
conflicts = action_conflicts.setdefault(mutex_action, [])
conflicts.extend(group_actions[:i])
conflicts.extend(group_actions[i + 1:])
# find all option indices, and determine the arg_string_pattern
# which has an 'O' if there is an option at an index,
# an 'A' if there is an argument, or a '-' if there is a '--'
option_string_indices = {}
arg_string_pattern_parts = []
arg_strings_iter = iter(arg_strings)
for i, arg_string in enumerate(arg_strings_iter):
# all args after -- are non-options
if arg_string == '--':
arg_string_pattern_parts.append('-')
for arg_string in arg_strings_iter:
arg_string_pattern_parts.append('A')
# otherwise, add the arg to the arg strings
# and note the index if it was an option
else:
option_tuple = self._parse_optional(arg_string)
if option_tuple is None:
pattern = 'A'
else:
option_string_indices[i] = option_tuple
pattern = 'O'
arg_string_pattern_parts.append(pattern)
# join the pieces together to form the pattern
arg_strings_pattern = ''.join(arg_string_pattern_parts)
# converts arg strings to the appropriate and then takes the action
seen_actions = _set()
seen_non_default_actions = _set()
def take_action(action, argument_strings, option_string=None):
seen_actions.add(action)
argument_values = self._get_values(action, argument_strings)
# error if this argument is not allowed with other previously
# seen arguments, assuming that actions that use the default
# value don't really count as "present"
if argument_values is not action.default:
seen_non_default_actions.add(action)
for conflict_action in action_conflicts.get(action, []):
if conflict_action in seen_non_default_actions:
msg = _('not allowed with argument %s')
action_name = _get_action_name(conflict_action)
raise ArgumentError(action, msg % action_name)
# take the action if we didn't receive a SUPPRESS value
# (e.g. from a default)
if argument_values is not SUPPRESS:
action(self, namespace, argument_values, option_string)
# function to convert arg_strings into an optional action
def consume_optional(start_index):
# get the optional identified at this index
option_tuple = option_string_indices[start_index]
action, option_string, explicit_arg = option_tuple
# identify additional optionals in the same arg string
# (e.g. -xyz is the same as -x -y -z if no args are required)
match_argument = self._match_argument
action_tuples = []
while True:
# if we found no optional action, skip it
if action is None:
extras.append(arg_strings[start_index])
return start_index + 1
# if there is an explicit argument, try to match the
# optional's string arguments to only this
if explicit_arg is not None:
arg_count = match_argument(action, 'A')
# if the action is a single-dash option and takes no
# arguments, try to parse more single-dash options out
# of the tail of the option string
chars = self.prefix_chars
if arg_count == 0 and option_string[1] not in chars:
action_tuples.append((action, [], option_string))
for char in self.prefix_chars:
option_string = char + explicit_arg[0]
explicit_arg = explicit_arg[1:] or None
optionals_map = self._option_string_actions
if option_string in optionals_map:
action = optionals_map[option_string]
break
else:
msg = _('ignored explicit argument %r')
raise ArgumentError(action, msg % explicit_arg)
# if the action expect exactly one argument, we've
# successfully matched the option; exit the loop
elif arg_count == 1:
stop = start_index + 1
args = [explicit_arg]
action_tuples.append((action, args, option_string))
break
# error if a double-dash option did not use the
# explicit argument
else:
msg = _('ignored explicit argument %r')
raise ArgumentError(action, msg % explicit_arg)
# if there is no explicit argument, try to match the
# optional's string arguments with the following strings
# if successful, exit the loop
else:
start = start_index + 1
selected_patterns = arg_strings_pattern[start:]
arg_count = match_argument(action, selected_patterns)
stop = start + arg_count
args = arg_strings[start:stop]
action_tuples.append((action, args, option_string))
break
# add the Optional to the list and return the index at which
# the Optional's string args stopped
assert action_tuples
for action, args, option_string in action_tuples:
take_action(action, args, option_string)
return stop
# the list of Positionals left to be parsed; this is modified
# by consume_positionals()
positionals = self._get_positional_actions()
# function to convert arg_strings into positional actions
def consume_positionals(start_index):
# match as many Positionals as possible
match_partial = self._match_arguments_partial
selected_pattern = arg_strings_pattern[start_index:]
arg_counts = match_partial(positionals, selected_pattern)
# slice off the appropriate arg strings for each Positional
# and add the Positional and its args to the list
for action, arg_count in zip(positionals, arg_counts):
args = arg_strings[start_index: start_index + arg_count]
start_index += arg_count
take_action(action, args)
# slice off the Positionals that we just parsed and return the
# index at which the Positionals' string args stopped
positionals[:] = positionals[len(arg_counts):]
return start_index
# consume Positionals and Optionals alternately, until we have
# passed the last option string
extras = []
start_index = 0
if option_string_indices:
max_option_string_index = max(option_string_indices)
else:
max_option_string_index = -1
while start_index <= max_option_string_index:
# consume any Positionals preceding the next option
next_option_string_index = min([
index
for index in option_string_indices
if index >= start_index])
if start_index != next_option_string_index:
positionals_end_index = consume_positionals(start_index)
# only try to parse the next optional if we didn't consume
# the option string during the positionals parsing
if positionals_end_index > start_index:
start_index = positionals_end_index
continue
else:
start_index = positionals_end_index
# if we consumed all the positionals we could and we're not
# at the index of an option string, there were extra arguments
if start_index not in option_string_indices:
strings = arg_strings[start_index:next_option_string_index]
extras.extend(strings)
start_index = next_option_string_index
# consume the next optional and any arguments for it
start_index = consume_optional(start_index)
# consume any positionals following the last Optional
stop_index = consume_positionals(start_index)
# if we didn't consume all the argument strings, there were extras
extras.extend(arg_strings[stop_index:])
# if we didn't use all the Positional objects, there were too few
# arg strings supplied.
if positionals:
self.error(_('too few arguments'))
# make sure all required actions were present
for action in self._actions:
if action.required:
if action not in seen_actions:
name = _get_action_name(action)
self.error(_('argument %s is required') % name)
# make sure all required groups had one option present
for group in self._mutually_exclusive_groups:
if group.required:
for action in group._group_actions:
if action in seen_non_default_actions:
break
# if no actions were used, report the error
else:
names = [_get_action_name(action)
for action in group._group_actions
if action.help is not SUPPRESS]
msg = _('one of the arguments %s is required')
self.error(msg % ' '.join(names))
# return the updated namespace and the extra arguments
return namespace, extras
def _read_args_from_files(self, arg_strings):
# expand arguments referencing files
new_arg_strings = []
for arg_string in arg_strings:
# for regular arguments, just add them back into the list
if arg_string[0] not in self.fromfile_prefix_chars:
new_arg_strings.append(arg_string)
# replace arguments referencing files with the file content
else:
try:
args_file = open(arg_string[1:])
try:
arg_strings = []
for arg_line in args_file.read().splitlines():
for arg in self.convert_arg_line_to_args(arg_line):
arg_strings.append(arg)
arg_strings = self._read_args_from_files(arg_strings)
new_arg_strings.extend(arg_strings)
finally:
args_file.close()
except IOError:
err = _sys.exc_info()[1]
self.error(str(err))
# return the modified argument list
return new_arg_strings
def convert_arg_line_to_args(self, arg_line):
return [arg_line]
def _match_argument(self, action, arg_strings_pattern):
# match the pattern for this action to the arg strings
nargs_pattern = self._get_nargs_pattern(action)
match = _re.match(nargs_pattern, arg_strings_pattern)
# raise an exception if we weren't able to find a match
if match is None:
nargs_errors = {
None: _('expected one argument'),
OPTIONAL: _('expected at most one argument'),
ONE_OR_MORE: _('expected at least one argument'),
}
default = _('expected %s argument(s)') % action.nargs
msg = nargs_errors.get(action.nargs, default)
raise ArgumentError(action, msg)
# return the number of arguments matched
return len(match.group(1))
def _match_arguments_partial(self, actions, arg_strings_pattern):
# progressively shorten the actions list by slicing off the
# final actions until we find a match
result = []
for i in range(len(actions), 0, -1):
actions_slice = actions[:i]
pattern = ''.join([self._get_nargs_pattern(action)
for action in actions_slice])
match = _re.match(pattern, arg_strings_pattern)
if match is not None:
result.extend([len(string) for string in match.groups()])
break
# return the list of arg string counts
return result
def _parse_optional(self, arg_string):
# if it's an empty string, it was meant to be a positional
if not arg_string:
return None
# if it doesn't start with a prefix, it was meant to be positional
if not arg_string[0] in self.prefix_chars:
return None
# if the option string is present in the parser, return the action
if arg_string in self._option_string_actions:
action = self._option_string_actions[arg_string]
return action, arg_string, None
# if it's just a single character, it was meant to be positional
if len(arg_string) == 1:
return None
# if the option string before the "=" is present, return the action
if '=' in arg_string:
option_string, explicit_arg = arg_string.split('=', 1)
if option_string in self._option_string_actions:
action = self._option_string_actions[option_string]
return action, option_string, explicit_arg
# search through all possible prefixes of the option string
# and all actions in the parser for possible interpretations
option_tuples = self._get_option_tuples(arg_string)
# if multiple actions match, the option string was ambiguous
if len(option_tuples) > 1:
options = ', '.join([option_string
for action, option_string, explicit_arg in option_tuples])
tup = arg_string, options
self.error(_('ambiguous option: %s could match %s') % tup)
# if exactly one action matched, this segmentation is good,
# so return the parsed action
elif len(option_tuples) == 1:
option_tuple, = option_tuples
return option_tuple
# if it was not found as an option, but it looks like a negative
# number, it was meant to be positional
# unless there are negative-number-like options
if self._negative_number_matcher.match(arg_string):
if not self._has_negative_number_optionals:
return None
# if it contains a space, it was meant to be a positional
if ' ' in arg_string:
return None
# it was meant to be an optional but there is no such option
# in this parser (though it might be a valid option in a subparser)
return None, arg_string, None
def _get_option_tuples(self, option_string):
result = []
# option strings starting with two prefix characters are only
# split at the '='
chars = self.prefix_chars
if option_string[0] in chars and option_string[1] in chars:
if '=' in option_string:
option_prefix, explicit_arg = option_string.split('=', 1)
else:
option_prefix = option_string
explicit_arg = None
for option_string in self._option_string_actions:
if option_string.startswith(option_prefix):
action = self._option_string_actions[option_string]
tup = action, option_string, explicit_arg
result.append(tup)
# single character options can be concatenated with their arguments
# but multiple character options always have to have their argument
# separate
elif option_string[0] in chars and option_string[1] not in chars:
option_prefix = option_string
explicit_arg = None
short_option_prefix = option_string[:2]
short_explicit_arg = option_string[2:]
for option_string in self._option_string_actions:
if option_string == short_option_prefix:
action = self._option_string_actions[option_string]
tup = action, option_string, short_explicit_arg
result.append(tup)
elif option_string.startswith(option_prefix):
action = self._option_string_actions[option_string]
tup = action, option_string, explicit_arg
result.append(tup)
# shouldn't ever get here
else:
self.error(_('unexpected option string: %s') % option_string)
# return the collected option tuples
return result
def _get_nargs_pattern(self, action):
# in all examples below, we have to allow for '--' args
# which are represented as '-' in the pattern
nargs = action.nargs
# the default (None) is assumed to be a single argument
if nargs is None:
nargs_pattern = '(-*A-*)'
# allow zero or one arguments
elif nargs == OPTIONAL:
nargs_pattern = '(-*A?-*)'
# allow zero or more arguments
elif nargs == ZERO_OR_MORE:
nargs_pattern = '(-*[A-]*)'
# allow one or more arguments
elif nargs == ONE_OR_MORE:
nargs_pattern = '(-*A[A-]*)'
# allow any number of options or arguments
elif nargs == REMAINDER:
nargs_pattern = '([-AO]*)'
# allow one argument followed by any number of options or arguments
elif nargs == PARSER:
nargs_pattern = '(-*A[-AO]*)'
# all others should be integers
else:
nargs_pattern = '(-*%s-*)' % '-*'.join('A' * nargs)
# if this is an optional action, -- is not allowed
if action.option_strings:
nargs_pattern = nargs_pattern.replace('-*', '')
nargs_pattern = nargs_pattern.replace('-', '')
# return the pattern
return nargs_pattern
# ========================
# Value conversion methods
# ========================
def _get_values(self, action, arg_strings):
# for everything but PARSER args, strip out '--'
if action.nargs not in [PARSER, REMAINDER]:
arg_strings = [s for s in arg_strings if s != '--']
# optional argument produces a default when not present
if not arg_strings and action.nargs == OPTIONAL:
if action.option_strings:
value = action.const
else:
value = action.default
if isinstance(value, _basestring):
value = self._get_value(action, value)
self._check_value(action, value)
# when nargs='*' on a positional, if there were no command-line
# args, use the default if it is anything other than None
elif (not arg_strings and action.nargs == ZERO_OR_MORE and
not action.option_strings):
if action.default is not None:
value = action.default
else:
value = arg_strings
self._check_value(action, value)
# single argument or optional argument produces a single value
elif len(arg_strings) == 1 and action.nargs in [None, OPTIONAL]:
arg_string, = arg_strings
value = self._get_value(action, arg_string)
self._check_value(action, value)
# REMAINDER arguments convert all values, checking none
elif action.nargs == REMAINDER:
value = [self._get_value(action, v) for v in arg_strings]
# PARSER arguments convert all values, but check only the first
elif action.nargs == PARSER:
value = [self._get_value(action, v) for v in arg_strings]
self._check_value(action, value[0])
# all other types of nargs produce a list
else:
value = [self._get_value(action, v) for v in arg_strings]
for v in value:
self._check_value(action, v)
# return the converted value
return value
def _get_value(self, action, arg_string):
type_func = self._registry_get('type', action.type, action.type)
if not _callable(type_func):
msg = _('%r is not callable')
raise ArgumentError(action, msg % type_func)
# convert the value to the appropriate type
try:
result = type_func(arg_string)
# ArgumentTypeErrors indicate errors
except ArgumentTypeError:
name = getattr(action.type, '__name__', repr(action.type))
msg = str(_sys.exc_info()[1])
raise ArgumentError(action, msg)
# TypeErrors or ValueErrors also indicate errors
except (TypeError, ValueError):
name = getattr(action.type, '__name__', repr(action.type))
msg = _('invalid %s value: %r')
raise ArgumentError(action, msg % (name, arg_string))
# return the converted value
return result
def _check_value(self, action, value):
# converted value must be one of the choices (if specified)
if action.choices is not None and value not in action.choices:
tup = value, ', '.join(map(repr, action.choices))
msg = _('invalid choice: %r (choose from %s)') % tup
raise ArgumentError(action, msg)
# =======================
# Help-formatting methods
# =======================
def format_usage(self):
formatter = self._get_formatter()
formatter.add_usage(self.usage, self._actions,
self._mutually_exclusive_groups)
return formatter.format_help()
def format_help(self):
formatter = self._get_formatter()
# usage
formatter.add_usage(self.usage, self._actions,
self._mutually_exclusive_groups)
# description
formatter.add_text(self.description)
# positionals, optionals and user-defined groups
for action_group in self._action_groups:
formatter.start_section(action_group.title)
formatter.add_text(action_group.description)
formatter.add_arguments(action_group._group_actions)
formatter.end_section()
# epilog
formatter.add_text(self.epilog)
# determine help from format above
return formatter.format_help()
def format_version(self):
import warnings
warnings.warn(
'The format_version method is deprecated -- the "version" '
'argument to ArgumentParser is no longer supported.',
DeprecationWarning)
formatter = self._get_formatter()
formatter.add_text(self.version)
return formatter.format_help()
def _get_formatter(self):
return self.formatter_class(prog=self.prog)
# =====================
# Help-printing methods
# =====================
def print_usage(self, file=None):
if file is None:
file = _sys.stdout
self._print_message(self.format_usage(), file)
def print_help(self, file=None):
if file is None:
file = _sys.stdout
self._print_message(self.format_help(), file)
def print_version(self, file=None):
import warnings
warnings.warn(
'The print_version method is deprecated -- the "version" '
'argument to ArgumentParser is no longer supported.',
DeprecationWarning)
self._print_message(self.format_version(), file)
def _print_message(self, message, file=None):
if message:
if file is None:
file = _sys.stderr
file.write(message)
# ===============
# Exiting methods
# ===============
def exit(self, status=0, message=None):
if message:
self._print_message(message, _sys.stderr)
_sys.exit(status)
def error(self, message):
"""error(message: string)
Prints a usage message incorporating the message to stderr and
exits.
If you override this in a subclass, it should not return -- it
should either exit or raise an exception.
"""
self.print_usage(_sys.stderr)
self.exit(2, _('%s: error: %s\n') % (self.prog, message))
Lib/test/test_argparse.py 0 → 100644
View file @ 6d265699
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Misc/NEWS
View file @ 6d265699
......@@ -722,6 +722,8 @@ Library
- Issue #6729: Added ctypes.c_ssize_t to represent ssize_t.
- Issue #6247: The argparse module has been added to the standard library.
Extension Modules
-----------------
......
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