Issue #16827: Make Interpreter introduction section of the tutorial more

focussed and move advanced section and customization information to a separate
file called appendix.

Patch credits: Jamayla Wiley, Ya-Ting Huang and James Brewer.

Doc/tutorial/appendix.rst

+.. _tut-appendix:
+
+********
+Appendix
+********
+
+
+.. _tut-interac:
+
+Interactive Mode
+================
+
+.. _tut-error:
+
+Error Handling
+--------------
+
+When an error occurs, the interpreter prints an error message and a stack trace.
+In interactive mode, it then returns to the primary prompt; when input came from
+a file, it exits with a nonzero exit status after printing the stack trace.
+(Exceptions handled by an :keyword:`except` clause in a :keyword:`try` statement
+are not errors in this context.)  Some errors are unconditionally fatal and
+cause an exit with a nonzero exit; this applies to internal inconsistencies and
+some cases of running out of memory.  All error messages are written to the
+standard error stream; normal output from executed commands is written to
+standard output.
+
+Typing the interrupt character (usually Control-C or DEL) to the primary or
+secondary prompt cancels the input and returns to the primary prompt. [#]_
+Typing an interrupt while a command is executing raises the
+:exc:`KeyboardInterrupt` exception, which may be handled by a :keyword:`try`
+statement.
+
+
+.. _tut-scripts:
+
+Executable Python Scripts
+-------------------------
+
+On BSD'ish Unix systems, Python scripts can be made directly executable, like
+shell scripts, by putting the line ::
+
+   #!/usr/bin/env python
+
+(assuming that the interpreter is on the user's :envvar:`PATH`) at the beginning
+of the script and giving the file an executable mode.  The ``#!`` must be the
+first two characters of the file.  On some platforms, this first line must end
+with a Unix-style line ending (``'\n'``), not a Windows (``'\r\n'``) line
+ending.  Note that the hash, or pound, character, ``'#'``, is used to start a
+comment in Python.
+
+The script can be given an executable mode, or permission, using the
+:program:`chmod` command.
+
+.. code-block:: bash
+
+   $ chmod +x myscript.py
+
+On Windows systems, there is no notion of an "executable mode".  The Python
+installer automatically associates ``.py`` files with ``python.exe`` so that
+a double-click on a Python file will run it as a script.  The extension can
+also be ``.pyw``, in that case, the console window that normally appears is
+suppressed.
+
+
+.. _tut-startup:
+
+The Interactive Startup File
+----------------------------
+
+When you use Python interactively, it is frequently handy to have some standard
+commands executed every time the interpreter is started.  You can do this by
+setting an environment variable named :envvar:`PYTHONSTARTUP` to the name of a
+file containing your start-up commands.  This is similar to the :file:`.profile`
+feature of the Unix shells.
+
+This file is only read in interactive sessions, not when Python reads commands
+from a script, and not when :file:`/dev/tty` is given as the explicit source of
+commands (which otherwise behaves like an interactive session).  It is executed
+in the same namespace where interactive commands are executed, so that objects
+that it defines or imports can be used without qualification in the interactive
+session. You can also change the prompts ``sys.ps1`` and ``sys.ps2`` in this
+file.
+
+If you want to read an additional start-up file from the current directory, you
+can program this in the global start-up file using code like ``if
+os.path.isfile('.pythonrc.py'): exec(open('.pythonrc.py').read())``.
+If you want to use the startup file in a script, you must do this explicitly
+in the script::
+
+   import os
+   filename = os.environ.get('PYTHONSTARTUP')
+   if filename and os.path.isfile(filename):
+       with open(filename) as fobj:
+          startup_file = fobj.read()
+       exec(startup_file)
+
+
+.. _tut-customize:
+
+The Customization Modules
+-------------------------
+
+Python provides two hooks to let you customize it: :mod:`sitecustomize` and
+:mod:`usercustomize`.  To see how it works, you need first to find the location
+of your user site-packages directory.  Start Python and run this code::
+
+   >>> import site
+   >>> site.getusersitepackages()
+   '/home/user/.local/lib/python2.7/site-packages'
+
+Now you can create a file named :file:`usercustomize.py` in that directory and
+put anything you want in it.  It will affect every invocation of Python, unless
+it is started with the :option:`-s` option to disable the automatic import.
+
+:mod:`sitecustomize` works in the same way, but is typically created by an
+administrator of the computer in the global site-packages directory, and is
+imported before :mod:`usercustomize`.  See the documentation of the :mod:`site`
+module for more details.
+
+
+.. rubric:: Footnotes
+
+.. [#] A problem with the GNU Readline package may prevent this.

Doc/tutorial/index.rst

@@ -56,3 +56,4 @@ The :ref:`glossary` is also worth going through.
    whatnow.rst
    interactive.rst
    floatingpoint.rst
+   appendix.rst

Doc/tutorial/interpreter.rst

@@ -108,63 +108,15 @@ example, take a look at this :keyword:`if` statement::
    Be careful not to fall off!
 
 
+For more on interactive mode, see :ref:`tut-interac`.
+
+
 .. _tut-interp:
 
 The Interpreter and Its Environment
 ===================================
 
 
-.. _tut-error:
-
-Error Handling
---------------
-
-When an error occurs, the interpreter prints an error message and a stack trace.
-In interactive mode, it then returns to the primary prompt; when input came from
-a file, it exits with a nonzero exit status after printing the stack trace.
-(Exceptions handled by an :keyword:`except` clause in a :keyword:`try` statement
-are not errors in this context.)  Some errors are unconditionally fatal and
-cause an exit with a nonzero exit; this applies to internal inconsistencies and
-some cases of running out of memory.  All error messages are written to the
-standard error stream; normal output from executed commands is written to
-standard output.
-
-Typing the interrupt character (usually Control-C or DEL) to the primary or
-secondary prompt cancels the input and returns to the primary prompt. [#]_
-Typing an interrupt while a command is executing raises the
-:exc:`KeyboardInterrupt` exception, which may be handled by a :keyword:`try`
-statement.
-
-
-.. _tut-scripts:
-
-Executable Python Scripts
--------------------------
-
-On BSD'ish Unix systems, Python scripts can be made directly executable, like
-shell scripts, by putting the line ::
-
-   #! /usr/bin/env python
-
-(assuming that the interpreter is on the user's :envvar:`PATH`) at the beginning
-of the script and giving the file an executable mode.  The ``#!`` must be the
-first two characters of the file.  On some platforms, this first line must end
-with a Unix-style line ending (``'\n'``), not a Windows (``'\r\n'``) line
-ending.  Note that the hash, or pound, character, ``'#'``, is used to start a
-comment in Python.
-
-The script can be given an executable mode, or permission, using the
-:program:`chmod` command::
-
-   $ chmod +x myscript.py
-
-On Windows systems, there is no notion of an "executable mode".  The Python
-installer automatically associates ``.py`` files with ``python.exe`` so that
-a double-click on a Python file will run it as a script.  The extension can
-also be ``.pyw``, in that case, the console window that normally appears is
-suppressed.
-
-
 .. _tut-source-encoding:
 
 Source Code Encoding
@@ -207,63 +159,3 @@ supported. To display all these characters properly, your editor must recognize
 that the file is UTF-8, and it must use a font that supports all the characters
 in the file.
 
-
-.. _tut-startup:
-
-The Interactive Startup File
-----------------------------
-
-When you use Python interactively, it is frequently handy to have some standard
-commands executed every time the interpreter is started.  You can do this by
-setting an environment variable named :envvar:`PYTHONSTARTUP` to the name of a
-file containing your start-up commands.  This is similar to the :file:`.profile`
-feature of the Unix shells.
-
-.. XXX This should probably be dumped in an appendix, since most people
-   don't use Python interactively in non-trivial ways.
-
-This file is only read in interactive sessions, not when Python reads commands
-from a script, and not when :file:`/dev/tty` is given as the explicit source of
-commands (which otherwise behaves like an interactive session).  It is executed
-in the same namespace where interactive commands are executed, so that objects
-that it defines or imports can be used without qualification in the interactive
-session. You can also change the prompts ``sys.ps1`` and ``sys.ps2`` in this
-file.
-
-If you want to read an additional start-up file from the current directory, you
-can program this in the global start-up file using code like ``if
-os.path.isfile('.pythonrc.py'): execfile('.pythonrc.py')``.  If you want to use
-the startup file in a script, you must do this explicitly in the script::
-
-   import os
-   filename = os.environ.get('PYTHONSTARTUP')
-   if filename and os.path.isfile(filename):
-       execfile(filename)
-
-
-.. _tut-customize:
-
-The Customization Modules
--------------------------
-
-Python provides two hooks to let you customize it: :mod:`sitecustomize` and
-:mod:`usercustomize`.  To see how it works, you need first to find the location
-of your user site-packages directory.  Start Python and run this code:
-
-   >>> import site
-   >>> site.getusersitepackages()
-   '/home/user/.local/lib/python2.7/site-packages'
-
-Now you can create a file named :file:`usercustomize.py` in that directory and
-put anything you want in it.  It will affect every invocation of Python, unless
-it is started with the :option:`-s` option to disable the automatic import.
-
-:mod:`sitecustomize` works in the same way, but is typically created by an
-administrator of the computer in the global site-packages directory, and is
-imported before :mod:`usercustomize`.  See the documentation of the :mod:`site`
-module for more details.
-
-
-.. rubric:: Footnotes
-
-.. [#] A problem with the GNU Readline package may prevent this.