Commit 6d3dfc3f authored by Alexandre Vassalotti's avatar Alexandre Vassalotti

Merged revisions...

Merged revisions 74074,74077,74111,74188,74192-74193,74200,74252-74253,74258-74261 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk

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  r74074 | georg.brandl | 2009-07-18 05:03:10 -0400 (Sat, 18 Jul 2009) | 1 line

  #6513: fix example code: warning categories are classes, not instances.
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  r74077 | georg.brandl | 2009-07-18 05:43:40 -0400 (Sat, 18 Jul 2009) | 1 line

  #6489: fix an ambiguity in getiterator() documentation.
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  r74111 | benjamin.peterson | 2009-07-20 09:30:10 -0400 (Mon, 20 Jul 2009) | 1 line

  remove docs for deprecated -p option
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  r74188 | benjamin.peterson | 2009-07-23 10:25:31 -0400 (Thu, 23 Jul 2009) | 1 line

  use bools
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  r74192 | georg.brandl | 2009-07-24 12:28:38 -0400 (Fri, 24 Jul 2009) | 1 line

  Fix arg types of et#.
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  r74193 | georg.brandl | 2009-07-24 12:46:38 -0400 (Fri, 24 Jul 2009) | 1 line

  Dont put "void" in signature for nullary functions.
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  r74200 | georg.brandl | 2009-07-25 09:02:15 -0400 (Sat, 25 Jul 2009) | 1 line

  #6571: add index entries for more operators.
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  r74252 | georg.brandl | 2009-07-29 12:06:31 -0400 (Wed, 29 Jul 2009) | 1 line

  #6593: fix link targets.
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  r74253 | georg.brandl | 2009-07-29 12:09:17 -0400 (Wed, 29 Jul 2009) | 1 line

  #6591: add reference to ioctl in fcntl module for platforms other than Windows.
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  r74258 | georg.brandl | 2009-07-29 12:57:05 -0400 (Wed, 29 Jul 2009) | 1 line

  Add a link to readline, and mention IPython and bpython.
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  r74259 | georg.brandl | 2009-07-29 13:07:21 -0400 (Wed, 29 Jul 2009) | 1 line

  Fix some markup and small factual glitches found by M. Markert.
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  r74260 | georg.brandl | 2009-07-29 13:15:20 -0400 (Wed, 29 Jul 2009) | 1 line

  Fix a few markup glitches.
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  r74261 | georg.brandl | 2009-07-29 13:50:25 -0400 (Wed, 29 Jul 2009) | 1 line

  Rewrite the section about classes a bit; mostly tidbits, and a larger update to the section about "private" variables to reflect the Pythonic consensus better.
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parent fc230e8c
...@@ -160,7 +160,7 @@ variable(s) whose address should be passed. ...@@ -160,7 +160,7 @@ variable(s) whose address should be passed.
In both cases, *\*buffer_length* is set to the length of the encoded data In both cases, *\*buffer_length* is set to the length of the encoded data
without the trailing NUL byte. without the trailing NUL byte.
``et#`` (string, Unicode object or character buffer compatible object) [const char \*encoding, char \*\*buffer] ``et#`` (string, Unicode object or character buffer compatible object) [const char \*encoding, char \*\*buffer, int \*buffer_length]
Same as ``es#`` except that string objects are passed through without recoding Same as ``es#`` except that string objects are passed through without recoding
them. Instead, the implementation assumes that the string object uses the them. Instead, the implementation assumes that the string object uses the
encoding passed in as parameter. encoding passed in as parameter.
......
...@@ -64,16 +64,16 @@ Floating Point Objects ...@@ -64,16 +64,16 @@ Floating Point Objects
around the header file :file:`float.h`. around the header file :file:`float.h`.
.. cfunction:: double PyFloat_GetMax(void) .. cfunction:: double PyFloat_GetMax()
Return the maximum representable finite float *DBL_MAX* as C :ctype:`double`. Return the maximum representable finite float *DBL_MAX* as C :ctype:`double`.
.. cfunction:: double PyFloat_GetMin(void) .. cfunction:: double PyFloat_GetMin()
Return the minimum normalized positive float *DBL_MIN* as C :ctype:`double`. Return the minimum normalized positive float *DBL_MIN* as C :ctype:`double`.
.. cfunction:: int PyFloat_ClearFreeList(void) .. cfunction:: int PyFloat_ClearFreeList()
Clear the float free list. Return the number of items that could not Clear the float free list. Return the number of items that could not
be freed. be freed.
...@@ -94,7 +94,7 @@ no longer available. ...@@ -94,7 +94,7 @@ no longer available.
Macro version of :cfunc:`PyMethod_Self` which avoids error checking. Macro version of :cfunc:`PyMethod_Self` which avoids error checking.
.. cfunction:: int PyMethod_ClearFreeList(void) .. cfunction:: int PyMethod_ClearFreeList()
Clear the free list. Return the total number of freed items. Clear the free list. Return the total number of freed items.
...@@ -73,7 +73,7 @@ accessible to C code. They all work with the current interpreter thread's ...@@ -73,7 +73,7 @@ accessible to C code. They all work with the current interpreter thread's
case *name* is deleted from the sys module. Returns ``0`` on success, ``-1`` case *name* is deleted from the sys module. Returns ``0`` on success, ``-1``
on error. on error.
.. cfunction:: void PySys_ResetWarnOptions(void) .. cfunction:: void PySys_ResetWarnOptions()
Reset :data:`sys.warnoptions` to an empty list. Reset :data:`sys.warnoptions` to an empty list.
......
...@@ -107,6 +107,6 @@ Tuple Objects ...@@ -107,6 +107,6 @@ Tuple Objects
raises :exc:`MemoryError` or :exc:`SystemError`. raises :exc:`MemoryError` or :exc:`SystemError`.
.. cfunction:: int PyTuple_ClearFreeList(void) .. cfunction:: int PyTuple_ClearFreeList()
Clear the free list. Return the total number of freed items. Clear the free list. Return the total number of freed items.
...@@ -33,7 +33,7 @@ Type Objects ...@@ -33,7 +33,7 @@ Type Objects
standard type object. Return false in all other cases. standard type object. Return false in all other cases.
.. cfunction:: unsigned int PyType_ClearCache(void) .. cfunction:: unsigned int PyType_ClearCache()
Clear the internal lookup cache. Return the current version tag. Clear the internal lookup cache. Return the current version tag.
......
...@@ -84,10 +84,11 @@ access internal read-only data of Unicode objects: ...@@ -84,10 +84,11 @@ access internal read-only data of Unicode objects:
:ctype:`PyUnicodeObject` (not checked). :ctype:`PyUnicodeObject` (not checked).
.. cfunction:: int PyUnicode_ClearFreeList(void) .. cfunction:: int PyUnicode_ClearFreeList()
Clear the free list. Return the total number of freed items. Clear the free list. Return the total number of freed items.
Unicode provides many different character properties. The most often needed ones Unicode provides many different character properties. The most often needed ones
are available through these macros which are mapped to C functions depending on are available through these macros which are mapped to C functions depending on
the Python configuration. the Python configuration.
......
...@@ -86,13 +86,6 @@ document could also be refactored with this option. ...@@ -86,13 +86,6 @@ document could also be refactored with this option.
The :option:`-v` option enables output of more information on the translation The :option:`-v` option enables output of more information on the translation
process. process.
When the :option:`-p` is passed, the :2to3fixer:`print` fixer ``print`` as a
function instead of a statement. This is useful when ``from __future__ import
print_function`` is being used. If this option is not given, the print fixer
will surround print calls in an extra set of parentheses because it cannot
differentiate between the print statement with parentheses (such as ``print
("a" + "b" + "c")``) and a true function call.
.. _2to3-fixers: .. _2to3-fixers:
......
...@@ -194,7 +194,7 @@ class can also install themselves in the built-in namespace as the function ...@@ -194,7 +194,7 @@ class can also install themselves in the built-in namespace as the function
:func:`translation`. :func:`translation`.
For the *names* parameter, please see the description of the translation For the *names* parameter, please see the description of the translation
object's :meth:`install` method. object's :meth:`~NullTranslations.install` method.
As seen below, you usually mark the strings in your application that are As seen below, you usually mark the strings in your application that are
candidates for translation, by wrapping them in a call to the :func:`_` candidates for translation, by wrapping them in a call to the :func:`_`
......
...@@ -555,6 +555,8 @@ correspond to Unix system calls applicable to sockets. ...@@ -555,6 +555,8 @@ correspond to Unix system calls applicable to sockets.
The :meth:`ioctl` method is a limited interface to the WSAIoctl system The :meth:`ioctl` method is a limited interface to the WSAIoctl system
interface. Please refer to the MSDN documentation for more information. interface. Please refer to the MSDN documentation for more information.
On other platforms, the generic :func:`fcntl.fcntl` and :func:`fcntl.ioctl`
functions may be used; they accept a socket object as their first argument.
.. method:: socket.listen(backlog) .. method:: socket.listen(backlog)
......
...@@ -120,25 +120,24 @@ Notes: ...@@ -120,25 +120,24 @@ Notes:
Comparisons Comparisons
=========== ===========
.. index:: pair: chaining; comparisons
There are eight comparison operations in Python. They all have the same
priority (which is higher than that of the Boolean operations). Comparisons can
be chained arbitrarily; for example, ``x < y <= z`` is equivalent to ``x < y and
y <= z``, except that *y* is evaluated only once (but in both cases *z* is not
evaluated at all when ``x < y`` is found to be false).
.. index:: .. index::
pair: chaining; comparisons
pair: operator; comparison pair: operator; comparison
operator: == operator: ==
operator: < operator: <
operator: >
operator: <= operator: <=
operator: >
operator: >= operator: >=
operator: != operator: !=
operator: is operator: is
operator: is not operator: is not
There are eight comparison operations in Python. They all have the same
priority (which is higher than that of the Boolean operations). Comparisons can
be chained arbitrarily; for example, ``x < y <= z`` is equivalent to ``x < y and
y <= z``, except that *y* is evaluated only once (but in both cases *z* is not
evaluated at all when ``x < y`` is found to be false).
This table summarizes the comparison operations: This table summarizes the comparison operations:
+------------+-------------------------+ +------------+-------------------------+
...@@ -248,6 +247,13 @@ and imaginary parts. ...@@ -248,6 +247,13 @@ and imaginary parts.
builtin: int builtin: int
builtin: float builtin: float
builtin: complex builtin: complex
operator: +
operator: -
operator: *
operator: /
operator: //
operator: %
operator: **
Python fully supports mixed arithmetic: when a binary arithmetic operator has Python fully supports mixed arithmetic: when a binary arithmetic operator has
operands of different numeric types, the operand with the "narrower" type is operands of different numeric types, the operand with the "narrower" type is
...@@ -368,7 +374,15 @@ modules. ...@@ -368,7 +374,15 @@ modules.
Bit-string Operations on Integer Types Bit-string Operations on Integer Types
-------------------------------------- --------------------------------------
.. _bit-string-operations: .. index::
triple: operations on; integer; types
pair: bit-string; operations
pair: shifting; operations
pair: masking; operations
operator: ^
operator: &
operator: <<
operator: >>
Integers support additional operations that make sense only for bit-strings. Integers support additional operations that make sense only for bit-strings.
Negative numbers are treated as their 2's complement value (this assumes a Negative numbers are treated as their 2's complement value (this assumes a
...@@ -400,12 +414,6 @@ This table lists the bit-string operations sorted in ascending priority ...@@ -400,12 +414,6 @@ This table lists the bit-string operations sorted in ascending priority
| ``~x`` | the bits of *x* inverted | | | ``~x`` | the bits of *x* inverted | |
+------------+--------------------------------+----------+ +------------+--------------------------------+----------+
.. index::
triple: operations on; integer; types
pair: bit-string; operations
pair: shifting; operations
pair: masking; operations
Notes: Notes:
(1) (1)
......
...@@ -206,7 +206,7 @@ check:: ...@@ -206,7 +206,7 @@ check::
fxn() fxn()
# Verify some things # Verify some things
assert len(w) == 1 assert len(w) == 1
assert isinstance(w[-1].category, DeprecationWarning) assert issubclass(w[-1].category, DeprecationWarning)
assert "deprecated" in str(w[-1].message) assert "deprecated" in str(w[-1].message)
One can also cause all warnings to be exceptions by using ``error`` instead of One can also cause all warnings to be exceptions by using ``error`` instead of
......
...@@ -46,14 +46,14 @@ The following exception is defined: ...@@ -46,14 +46,14 @@ The following exception is defined:
The following functions are defined: The following functions are defined:
.. function:: open(url[, new=0[, autoraise=1]]) .. function:: open(url[, new=0[, autoraise=True]])
Display *url* using the default browser. If *new* is 0, the *url* is opened in Display *url* using the default browser. If *new* is 0, the *url* is opened
the same browser window if possible. If *new* is 1, a new browser window is in the same browser window if possible. If *new* is 1, a new browser window
opened if possible. If *new* is 2, a new browser page ("tab") is opened if is opened if possible. If *new* is 2, a new browser page ("tab") is opened
possible. If *autoraise* is true, the window is raised if possible (note that if possible. If *autoraise* is ``True``, the window is raised if possible
under many window managers this will occur regardless of the setting of this (note that under many window managers this will occur regardless of the
variable). setting of this variable).
Note that on some platforms, trying to open a filename using this function, Note that on some platforms, trying to open a filename using this function,
may work and start the operating system's associated program. However, this may work and start the operating system's associated program. However, this
...@@ -175,7 +175,7 @@ Browser controllers provide these methods which parallel three of the ...@@ -175,7 +175,7 @@ Browser controllers provide these methods which parallel three of the
module-level convenience functions: module-level convenience functions:
.. method:: controller.open(url[, new[, autoraise=1]]) .. method:: controller.open(url[, new[, autoraise=True]])
Display *url* using the browser handled by this controller. If *new* is 1, a new Display *url* using the browser handled by this controller. If *new* is 1, a new
browser window is opened if possible. If *new* is 2, a new browser page ("tab") browser window is opened if possible. If *new* is 2, a new browser page ("tab")
......
...@@ -262,9 +262,9 @@ The following methods work on the element's children (subelements). ...@@ -262,9 +262,9 @@ The following methods work on the element's children (subelements).
.. method:: Element.getiterator([tag=None]) .. method:: Element.getiterator([tag=None])
Creates a tree iterator with the current element as the root. The iterator Creates a tree iterator with the current element as the root. The iterator
iterates over this element and all elements below it that match the given tag. iterates over this element and all elements below it, in document (depth first)
If tag is ``None`` or ``'*'`` then all elements are iterated over. Returns an order. If *tag* is not ``None`` or ``'*'``, only elements whose tag equals
iterable that provides element objects in document (depth first) order. *tag* are returned from the iterator.
.. method:: Element.insert(index, element) .. method:: Element.insert(index, element)
......
...@@ -12,44 +12,41 @@ user not to "break into the definition." The most important features of classes ...@@ -12,44 +12,41 @@ user not to "break into the definition." The most important features of classes
are retained with full power, however: the class inheritance mechanism allows are retained with full power, however: the class inheritance mechanism allows
multiple base classes, a derived class can override any methods of its base multiple base classes, a derived class can override any methods of its base
class or classes, and a method can call the method of a base class with the same class or classes, and a method can call the method of a base class with the same
name. Objects can contain an arbitrary amount of private data. name. Objects can contain an arbitrary amount of data.
In C++ terminology, normally class members (including the data members) are In C++ terminology, normally class members (including the data members) are
*public* (except see below :ref:`tut-private`), *public* (except see below :ref:`tut-private`),
and all member functions are *virtual*. There are no special constructors or and all member functions are *virtual*. As in Modula-3, there are no shorthands
destructors. As in Modula-3, there are no shorthands for referencing the for referencing the object's members from its methods: the method function is
object's members from its methods: the method function is declared with an declared with an explicit first argument representing the object, which is
explicit first argument representing the object, which is provided implicitly by provided implicitly by the call. As in Smalltalk, classes themselves are
the call. As in Smalltalk, classes themselves are objects, albeit in the wider objects. This provides semantics for importing and renaming. Unlike C++ and
sense of the word: in Python, all data types are objects. This provides Modula-3, built-in types can be used as base classes for extension by the user.
semantics for importing and renaming. Unlike C++ and Modula-3, built-in types Also, like in C++, most built-in operators with special syntax (arithmetic
can be used as base classes for extension by the user. Also, like in C++ but
unlike in Modula-3, most built-in operators with special syntax (arithmetic
operators, subscripting etc.) can be redefined for class instances. operators, subscripting etc.) can be redefined for class instances.
(Lacking universally accepted terminology to talk about classes, I will make
occasional use of Smalltalk and C++ terms. I would use Modula-3 terms, since
its object-oriented semantics are closer to those of Python than C++, but I
expect that few readers have heard of it.)
.. _tut-terminology:
A Word About Terminology .. _tut-object:
========================
Lacking universally accepted terminology to talk about classes, I will make A Word About Names and Objects
occasional use of Smalltalk and C++ terms. (I would use Modula-3 terms, since ==============================
its object-oriented semantics are closer to those of Python than C++, but I
expect that few readers have heard of it.)
Objects have individuality, and multiple names (in multiple scopes) can be bound Objects have individuality, and multiple names (in multiple scopes) can be bound
to the same object. This is known as aliasing in other languages. This is to the same object. This is known as aliasing in other languages. This is
usually not appreciated on a first glance at Python, and can be safely ignored usually not appreciated on a first glance at Python, and can be safely ignored
when dealing with immutable basic types (numbers, strings, tuples). However, when dealing with immutable basic types (numbers, strings, tuples). However,
aliasing has an (intended!) effect on the semantics of Python code involving aliasing has a possibly surprising effect on the semantics of Python code
mutable objects such as lists, dictionaries, and most types representing involving mutable objects such as lists, dictionaries, and most other types.
entities outside the program (files, windows, etc.). This is usually used to This is usually used to the benefit of the program, since aliases behave like
the benefit of the program, since aliases behave like pointers in some respects. pointers in some respects. For example, passing an object is cheap since only a
For example, passing an object is cheap since only a pointer is passed by the pointer is passed by the implementation; and if a function modifies an object
implementation; and if a function modifies an object passed as an argument, the passed as an argument, the caller will see the change --- this eliminates the
caller will see the change --- this eliminates the need for two different need for two different argument passing mechanisms as in Pascal.
argument passing mechanisms as in Pascal.
.. _tut-scopes: .. _tut-scopes:
...@@ -73,7 +70,7 @@ built-in exception names); the global names in a module; and the local names in ...@@ -73,7 +70,7 @@ built-in exception names); the global names in a module; and the local names in
a function invocation. In a sense the set of attributes of an object also form a function invocation. In a sense the set of attributes of an object also form
a namespace. The important thing to know about namespaces is that there is a namespace. The important thing to know about namespaces is that there is
absolutely no relation between names in different namespaces; for instance, two absolutely no relation between names in different namespaces; for instance, two
different modules may both define a function "maximize" without confusion --- different modules may both define a function ``maximize`` without confusion ---
users of the modules must prefix it with the module name. users of the modules must prefix it with the module name.
By the way, I use the word *attribute* for any name following a dot --- for By the way, I use the word *attribute* for any name following a dot --- for
...@@ -112,11 +109,13 @@ name attempts to find the name in the namespace. ...@@ -112,11 +109,13 @@ name attempts to find the name in the namespace.
Although scopes are determined statically, they are used dynamically. At any Although scopes are determined statically, they are used dynamically. At any
time during execution, there are at least three nested scopes whose namespaces time during execution, there are at least three nested scopes whose namespaces
are directly accessible: the innermost scope, which is searched first, contains are directly accessible:
the local names; the namespaces of any enclosing functions, which are searched
starting with the nearest enclosing scope; the middle scope, searched next, * the innermost scope, which is searched first, contains the local names
contains the current module's global names; and the outermost scope (searched * the scopes of any enclosing functions, which are searched starting with the
last) is the namespace containing built-in names. nearest enclosing scope, contains non-local, but also non-global names
* the next-to-last scope contains the current module's global names
* the outermost scope (searched last) is the namespace containing built-in names
If a name is declared global, then all references and assignments go directly to If a name is declared global, then all references and assignments go directly to
the middle scope containing the module's global names. To rebind variables the middle scope containing the module's global names. To rebind variables
...@@ -138,15 +137,15 @@ language definition is evolving towards static name resolution, at "compile" ...@@ -138,15 +137,15 @@ language definition is evolving towards static name resolution, at "compile"
time, so don't rely on dynamic name resolution! (In fact, local variables are time, so don't rely on dynamic name resolution! (In fact, local variables are
already determined statically.) already determined statically.)
A special quirk of Python is that -- if no :keyword:`global` or A special quirk of Python is that -- if no :keyword:`global` statement is in
:keyword:`nonlocal` statement is in effect -- assignments to names always go effect -- assignments to names always go into the innermost scope. Assignments
into the innermost scope. Assignments do not copy data --- they just bind names do not copy data --- they just bind names to objects. The same is true for
to objects. The same is true for deletions: the statement ``del x`` removes the deletions: the statement ``del x`` removes the binding of ``x`` from the
binding of ``x`` from the namespace referenced by the local scope. In fact, all namespace referenced by the local scope. In fact, all operations that introduce
operations that introduce new names use the local scope: in particular, import new names use the local scope: in particular, :keyword:`import` statements and
statements and function definitions bind the module or function name in the function definitions bind the module or function name in the local scope. (The
local scope. (The :keyword:`global` statement can be used to indicate that :keyword:`global` statement can be used to indicate that particular variables
particular variables live in the global scope.) live in the global scope.)
The :keyword:`global` statement can be used to indicate that particular The :keyword:`global` statement can be used to indicate that particular
variables live in the global scope and should be rebound there; the variables live in the global scope and should be rebound there; the
...@@ -424,9 +423,9 @@ glancing through a method. ...@@ -424,9 +423,9 @@ glancing through a method.
Often, the first argument of a method is called ``self``. This is nothing more Often, the first argument of a method is called ``self``. This is nothing more
than a convention: the name ``self`` has absolutely no special meaning to than a convention: the name ``self`` has absolutely no special meaning to
Python. (Note, however, that by not following the convention your code may be Python. Note, however, that by not following the convention your code may be
less readable to other Python programmers, and it is also conceivable that a less readable to other Python programmers, and it is also conceivable that a
*class browser* program might be written that relies upon such a convention.) *class browser* program might be written that relies upon such a convention.
Any function object that is a class attribute defines a method for instances of Any function object that is a class attribute defines a method for instances of
that class. It is not necessary that the function definition is textually that class. It is not necessary that the function definition is textually
...@@ -462,13 +461,13 @@ argument:: ...@@ -462,13 +461,13 @@ argument::
Methods may reference global names in the same way as ordinary functions. The Methods may reference global names in the same way as ordinary functions. The
global scope associated with a method is the module containing the class global scope associated with a method is the module containing the class
definition. (The class itself is never used as a global scope!) While one definition. (The class itself is never used as a global scope.) While one
rarely encounters a good reason for using global data in a method, there are rarely encounters a good reason for using global data in a method, there are
many legitimate uses of the global scope: for one thing, functions and modules many legitimate uses of the global scope: for one thing, functions and modules
imported into the global scope can be used by methods, as well as functions and imported into the global scope can be used by methods, as well as functions and
classes defined in it. Usually, the class containing the method is itself classes defined in it. Usually, the class containing the method is itself
defined in this global scope, and in the next section we'll find some good defined in this global scope, and in the next section we'll find some good
reasons why a method would want to reference its own class! reasons why a method would want to reference its own class.
Each value is an object, and therefore has a *class* (also called its *type*). Each value is an object, and therefore has a *class* (also called its *type*).
It is stored as ``object.__class__``. It is stored as ``object.__class__``.
...@@ -519,12 +518,12 @@ An overriding method in a derived class may in fact want to extend rather than ...@@ -519,12 +518,12 @@ An overriding method in a derived class may in fact want to extend rather than
simply replace the base class method of the same name. There is a simple way to simply replace the base class method of the same name. There is a simple way to
call the base class method directly: just call ``BaseClassName.methodname(self, call the base class method directly: just call ``BaseClassName.methodname(self,
arguments)``. This is occasionally useful to clients as well. (Note that this arguments)``. This is occasionally useful to clients as well. (Note that this
only works if the base class is defined or imported directly in the global only works if the base class is accessible as ``BaseClassName`` in the global
scope.) scope.)
Python has two built-in functions that work with inheritance: Python has two built-in functions that work with inheritance:
* Use :func:`isinstance` to check an object's type: ``isinstance(obj, int)`` * Use :func:`isinstance` to check an instance's type: ``isinstance(obj, int)``
will be ``True`` only if ``obj.__class__`` is :class:`int` or some class will be ``True`` only if ``obj.__class__`` is :class:`int` or some class
derived from :class:`int`. derived from :class:`int`.
...@@ -582,28 +581,30 @@ http://www.python.org/download/releases/2.3/mro/. ...@@ -582,28 +581,30 @@ http://www.python.org/download/releases/2.3/mro/.
Private Variables Private Variables
================= =================
There is limited support for class-private identifiers. Any identifier of the "Private" instance variables that cannot be accessed except from inside an
form ``__spam`` (at least two leading underscores, at most one trailing object, don't exist in Python. However, there is a convention that is followed
underscore) is textually replaced with ``_classname__spam``, where ``classname`` by most Python code: a name prefixed with an underscore (e.g. ``_spam``) should
is the current class name with leading underscore(s) stripped. This mangling is be treated as a non-public part of the API (whether it is a function, a method
done without regard to the syntactic position of the identifier, so it can be or a data member). It should be considered an implementation detail and subject
used to define class-private instance and class variables, methods, variables to change without notice.
stored in globals, and even variables stored in instances. private to this class
on instances of *other* classes. Truncation may occur when the mangled name Since there is a valid use-case for class-private members (namely to avoid name
would be longer than 255 characters. Outside classes, or when the class name clashes of names with names defined by subclasses), there is limited support for
consists of only underscores, no mangling occurs. such a mechanism, called :dfn:`name mangling`. Any identifier of the form
``__spam`` (at least two leading underscores, at most one trailing underscore)
Name mangling is intended to give classes an easy way to define "private" is textually replaced with ``_classname__spam``, where ``classname`` is the
instance variables and methods, without having to worry about instance variables current class name with leading underscore(s) stripped. This mangling is done
defined by derived classes, or mucking with instance variables by code outside without regard to the syntactic position of the identifier, so it can be used to
the class. Note that the mangling rules are designed mostly to avoid accidents; define class-private instance and class variables, methods, variables stored in
it still is possible for a determined soul to access or modify a variable that globals, and even variables stored in instances. Truncation may occur when the
is considered private. This can even be useful in special circumstances, such mangled name would be longer than 255 characters. Outside classes, or when the
as in the debugger, and that's one reason why this loophole is not closed. class name consists of only underscores, no mangling occurs.
(Buglet: derivation of a class with the same name as the base class makes use of
private variables of the base class possible.) Note that the mangling rules are designed mostly to avoid accidents; it still is
possible to access or modify a variable that is considered private. This can
Notice that code passed to ``exec()`` or ``eval()`` does not even be useful in special circumstances, such as in the debugger.
Notice that code passed to ``exec()``, ``eval()`` or ``execfile()`` does not
consider the classname of the invoking class to be the current class; this is consider the classname of the invoking class to be the current class; this is
similar to the effect of the ``global`` statement, the effect of which is similar to the effect of the ``global`` statement, the effect of which is
likewise restricted to code that is byte-compiled together. The same likewise restricted to code that is byte-compiled together. The same
...@@ -654,7 +655,7 @@ Exceptions Are Classes Too ...@@ -654,7 +655,7 @@ Exceptions Are Classes Too
User-defined exceptions are identified by classes as well. Using this mechanism User-defined exceptions are identified by classes as well. Using this mechanism
it is possible to create extensible hierarchies of exceptions. it is possible to create extensible hierarchies of exceptions.
There are two valid (semantic) forms for the raise statement:: There are two new valid (semantic) forms for the :keyword:`raise` statement::
raise Class raise Class
...@@ -665,10 +666,10 @@ class derived from it. The first form is a shorthand for:: ...@@ -665,10 +666,10 @@ class derived from it. The first form is a shorthand for::
raise Class() raise Class()
A class in an except clause is compatible with an exception if it is the same A class in an :keyword:`except` clause is compatible with an exception if it is
class or a base class thereof (but not the other way around --- an except clause the same class or a base class thereof (but not the other way around --- an
listing a derived class is not compatible with a base class). For example, the except clause listing a derived class is not compatible with a base class). For
following code will print B, C, D in that order:: example, the following code will print B, C, D in that order::
class B(Exception): class B(Exception):
pass pass
......
...@@ -130,16 +130,17 @@ Basic usage of the :meth:`str.format` method looks like this:: ...@@ -130,16 +130,17 @@ Basic usage of the :meth:`str.format` method looks like this::
We are the knights who say "Ni!" We are the knights who say "Ni!"
The brackets and characters within them (called format fields) are replaced with The brackets and characters within them (called format fields) are replaced with
the objects passed into the format method. The number in the brackets refers to the objects passed into the :meth:`~str.format` method. The number in the
the position of the object passed into the format method. :: brackets refers to the position of the object passed into the
:meth:`~str.format` method. ::
>>> print('{0} and {1}'.format('spam', 'eggs')) >>> print('{0} and {1}'.format('spam', 'eggs'))
spam and eggs spam and eggs
>>> print('{1} and {0}'.format('spam', 'eggs')) >>> print('{1} and {0}'.format('spam', 'eggs'))
eggs and spam eggs and spam
If keyword arguments are used in the format method, their values are referred to If keyword arguments are used in the :meth:`~str.format` method, their values
by using the name of the argument. :: are referred to by using the name of the argument. ::
>>> print('This {food} is {adjective}.'.format( >>> print('This {food} is {adjective}.'.format(
... food='spam', adjective='absolutely horrible')) ... food='spam', adjective='absolutely horrible'))
...@@ -160,7 +161,7 @@ truncates the Pi to three places after the decimal. ...@@ -160,7 +161,7 @@ truncates the Pi to three places after the decimal.
The value of PI is approximately 3.142. The value of PI is approximately 3.142.
Passing an integer after the ``':'`` will cause that field to be a minimum Passing an integer after the ``':'`` will cause that field to be a minimum
number of characters wide. This is useful for making tables pretty.:: number of characters wide. This is useful for making tables pretty. ::
>>> table = {'Sjoerd': 4127, 'Jack': 4098, 'Dcab': 7678} >>> table = {'Sjoerd': 4127, 'Jack': 4098, 'Dcab': 7678}
>>> for name, phone in table.items(): >>> for name, phone in table.items():
...@@ -181,7 +182,7 @@ square brackets ``'[]'`` to access the keys :: ...@@ -181,7 +182,7 @@ square brackets ``'[]'`` to access the keys ::
Jack: 4098; Sjoerd: 4127; Dcab: 8637678 Jack: 4098; Sjoerd: 4127; Dcab: 8637678
This could also be done by passing the table as keyword arguments with the '**' This could also be done by passing the table as keyword arguments with the '**'
notation.:: notation. ::
>>> table = {'Sjoerd': 4127, 'Jack': 4098, 'Dcab': 8637678} >>> table = {'Sjoerd': 4127, 'Jack': 4098, 'Dcab': 8637678}
>>> print('Jack: {Jack:d}; Sjoerd: {Sjoerd:d}; Dcab: {Dcab:d}'.format(**table)) >>> print('Jack: {Jack:d}; Sjoerd: {Sjoerd:d}; Dcab: {Dcab:d}'.format(**table))
...@@ -374,9 +375,9 @@ shorter than writing equivalent :keyword:`try`\ -\ :keyword:`finally` blocks:: ...@@ -374,9 +375,9 @@ shorter than writing equivalent :keyword:`try`\ -\ :keyword:`finally` blocks::
>>> f.closed >>> f.closed
True True
File objects have some additional methods, such as :meth:`isatty` and File objects have some additional methods, such as :meth:`~file.isatty` and
:meth:`truncate` which are less frequently used; consult the Library Reference :meth:`~file.truncate` which are less frequently used; consult the Library
for a complete guide to file objects. Reference for a complete guide to file objects.
.. _tut-pickle: .. _tut-pickle:
......
...@@ -6,8 +6,8 @@ Interactive Input Editing and History Substitution ...@@ -6,8 +6,8 @@ Interactive Input Editing and History Substitution
Some versions of the Python interpreter support editing of the current input Some versions of the Python interpreter support editing of the current input
line and history substitution, similar to facilities found in the Korn shell and line and history substitution, similar to facilities found in the Korn shell and
the GNU Bash shell. This is implemented using the *GNU Readline* library, which the GNU Bash shell. This is implemented using the `GNU Readline`_ library,
supports Emacs-style and vi-style editing. This library has its own which supports Emacs-style and vi-style editing. This library has its own
documentation which I won't duplicate here; however, the basics are easily documentation which I won't duplicate here; however, the basics are easily
explained. The interactive editing and history described here are optionally explained. The interactive editing and history described here are optionally
available in the Unix and Cygwin versions of the interpreter. available in the Unix and Cygwin versions of the interpreter.
...@@ -148,8 +148,8 @@ interpreter. :: ...@@ -148,8 +148,8 @@ interpreter. ::
.. _tut-commentary: .. _tut-commentary:
Commentary Alternatives to the Interactive Interpreter
========== ===========================================
This facility is an enormous step forward compared to earlier versions of the This facility is an enormous step forward compared to earlier versions of the
interpreter; however, some wishes are left: It would be nice if the proper interpreter; however, some wishes are left: It would be nice if the proper
...@@ -158,8 +158,12 @@ token is required next). The completion mechanism might use the interpreter's ...@@ -158,8 +158,12 @@ token is required next). The completion mechanism might use the interpreter's
symbol table. A command to check (or even suggest) matching parentheses, symbol table. A command to check (or even suggest) matching parentheses,
quotes, etc., would also be useful. quotes, etc., would also be useful.
.. % One alternative enhanced interactive interpreter that has been around for quite
Do we mention IPython? DUBOIS some time is `IPython`_, which features tab completion, object exploration and
advanced history management. It can also be thoroughly customized and embedded
into other applications. Another similar enhanced interactive environment is
`bpython`_.
.. rubric:: Footnotes .. rubric:: Footnotes
...@@ -167,3 +171,7 @@ quotes, etc., would also be useful. ...@@ -167,3 +171,7 @@ quotes, etc., would also be useful.
:envvar:`PYTHONSTARTUP` environment variable when you start an interactive :envvar:`PYTHONSTARTUP` environment variable when you start an interactive
interpreter. interpreter.
.. _GNU Readline: http://tiswww.case.edu/php/chet/readline/rltop.html
.. _IPython: http://ipython.scipy.org/
.. _bpython: http://www.bpython-interpreter.org/
...@@ -448,14 +448,14 @@ one would hope that this somehow goes out to the filesystem, finds which ...@@ -448,14 +448,14 @@ one would hope that this somehow goes out to the filesystem, finds which
submodules are present in the package, and imports them all. Unfortunately, submodules are present in the package, and imports them all. Unfortunately,
this operation does not work very well on Windows platforms, where the this operation does not work very well on Windows platforms, where the
filesystem does not always have accurate information about the case of a filesystem does not always have accurate information about the case of a
filename! On these platforms, there is no guaranteed way to know whether a file filename. On these platforms, there is no guaranteed way to know whether a file
:file:`ECHO.PY` should be imported as a module :mod:`echo`, :mod:`Echo` or :file:`ECHO.PY` should be imported as a module :mod:`echo`, :mod:`Echo` or
:mod:`ECHO`. (For example, Windows 95 has the annoying practice of showing all :mod:`ECHO`. (For example, Windows 95 has the annoying practice of showing all
file names with a capitalized first letter.) The DOS 8+3 filename restriction file names with a capitalized first letter.) The DOS 8+3 filename restriction
adds another interesting problem for long module names. adds another interesting problem for long module names.
The only solution is for the package author to provide an explicit index of the The only solution is for the package author to provide an explicit index of the
package. The import statement uses the following convention: if a package's package. The :keyword:`import` statement uses the following convention: if a package's
:file:`__init__.py` code defines a list named ``__all__``, it is taken to be the :file:`__init__.py` code defines a list named ``__all__``, it is taken to be the
list of module names that should be imported when ``from package import *`` is list of module names that should be imported when ``from package import *`` is
encountered. It is up to the package author to keep this list up-to-date when a encountered. It is up to the package author to keep this list up-to-date when a
...@@ -476,16 +476,16 @@ been imported (possibly running any initialization code in :file:`__init__.py`) ...@@ -476,16 +476,16 @@ been imported (possibly running any initialization code in :file:`__init__.py`)
and then imports whatever names are defined in the package. This includes any and then imports whatever names are defined in the package. This includes any
names defined (and submodules explicitly loaded) by :file:`__init__.py`. It names defined (and submodules explicitly loaded) by :file:`__init__.py`. It
also includes any submodules of the package that were explicitly loaded by also includes any submodules of the package that were explicitly loaded by
previous import statements. Consider this code:: previous :keyword:`import` statements. Consider this code::
import sound.effects.echo import sound.effects.echo
import sound.effects.surround import sound.effects.surround
from sound.effects import * from sound.effects import *
In this example, the echo and surround modules are imported in the current In this example, the :mod:`echo` and :mod:`surround` modules are imported in the
namespace because they are defined in the :mod:`sound.effects` package when the current namespace because they are defined in the :mod:`sound.effects` package
``from...import`` statement is executed. (This also works when ``__all__`` is when the ``from...import`` statement is executed. (This also works when
defined.) ``__all__`` is defined.)
Note that in general the practice of importing ``*`` from a module or package is Note that in general the practice of importing ``*`` from a module or package is
frowned upon, since it often causes poorly readable code. However, it is okay to frowned upon, since it often causes poorly readable code. However, it is okay to
...@@ -537,5 +537,6 @@ modules found in a package. ...@@ -537,5 +537,6 @@ modules found in a package.
.. rubric:: Footnotes .. rubric:: Footnotes
.. [#] In fact function definitions are also 'statements' that are 'executed'; the .. [#] In fact function definitions are also 'statements' that are 'executed'; the
execution enters the function name in the module's global symbol table. execution of a module-level function enters the function name in the module's
global symbol table.
...@@ -347,12 +347,15 @@ Decimal Floating Point Arithmetic ...@@ -347,12 +347,15 @@ Decimal Floating Point Arithmetic
The :mod:`decimal` module offers a :class:`Decimal` datatype for decimal The :mod:`decimal` module offers a :class:`Decimal` datatype for decimal
floating point arithmetic. Compared to the built-in :class:`float` floating point arithmetic. Compared to the built-in :class:`float`
implementation of binary floating point, the new class is especially helpful for implementation of binary floating point, the class is especially helpful for
financial applications and other uses which require exact decimal
representation, control over precision, control over rounding to meet legal or * financial applications and other uses which require exact decimal
regulatory requirements, tracking of significant decimal places, or for representation,
applications where the user expects the results to match calculations done by * control over precision,
hand. * control over rounding to meet legal or regulatory requirements,
* tracking of significant decimal places, or
* applications where the user expects the results to match calculations done by
hand.
For example, calculating a 5% tax on a 70 cent phone charge gives different For example, calculating a 5% tax on a 70 cent phone charge gives different
results in decimal floating point and binary floating point. The difference results in decimal floating point and binary floating point. The difference
......
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