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Add new directory "using". This should have been in the merge patch, 

but it was probably generated with "svn diff" so that new files that
weren't added first weren't included.
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.. highlightlang:: none
Command line and environment
============================
The CPython interpreter scans the command line and the environment for various
settings.
.. note::
Other implementation's command line schemes may differ. See
:ref:`implementations` for further resources.
Command line
------------
When invoking Python, you may specify any of these options::
python [-dEiOQStuUvxX?] [-c command | -m module-name | script | - ] [args]
The most common use case is, of course, a simple invocation of a script::
python myscript.py
Interface options
~~~~~~~~~~~~~~~~~
The interpreter interface resembles that of the UNIX shell:
* When called with standard input connected to a tty device, it prompts for
commands and executes them until an EOF (an end-of-file character, you can
produce that with *Ctrl-D* on UNIX or *Ctrl-Z, Enter* on Windows) is read.
* When called with a file name argument or with a file as standard input, it
reads and executes a script from that file.
* When called with ``-c command``, it executes the Python statement(s) given as
*command*. Here *command* may contain multiple statements separated by
newlines. Leading whitespace is significant in Python statements!
* When called with ``-m module-name``, the given module is searched on the
Python module path and executed as a script.
In non-interactive mode, the entire input is parsed before it is executed.
An interface option terminates the list of options consumed by the interpreter,
all consecutive arguments will end up in :data:`sys.argv` -- note that the first
element, subscript zero (``sys.argv[0]``), is a string reflecting the program's
source.
.. cmdoption:: -c <command>
Execute the Python code in *command*. *command* can be one ore more
statements separated by newlines, with significant leading whitespace as in
normal module code.
If this option is given, the first element of :data:`sys.argv` will be
``"-c"``.
.. cmdoption:: -m <module-name>
Search :data:`sys.path` for the named module and run the corresponding module
file as if it were executed with ``python modulefile.py`` as a script.
Since the argument is a *module* name, you must not give a file extension
(``.py``). However, the ``module-name`` does not have to be a valid Python
identifer (e.g. you can use a file name including a hyphen).
.. note::
This option cannot be used with builtin modules and extension modules
written in C, since they do not have Python module files.
If this option is given, the first element of :data:`sys.argv` will be the
full path to the module file.
Many standard library modules contain code that is invoked on their execution
as a script. An example is the :mod:`timeit` module::
python -mtimeit -s 'setup here' 'benchmarked code here'
python -mtimeit -h # for details
.. seealso::
:func:`runpy.run_module`
The actual implementation of this feature.
:pep:`338` -- Executing modules as scripts
.. describe:: <script>
Execute the Python code contained in *script*, which must be an (absolute or
relative) file name.
If this option is given, the first element of :data:`sys.argv` will be the
script file name as given on the command line.
.. describe:: -
Read commands from standard input (:data:`sys.stdin`). If standard input is
a terminal, :option:`-i` is implied.
If this option is given, the first element of :data:`sys.argv` will be
``"-"``.
.. seealso::
:ref:`tut-invoking`
If no script name is given, ``sys.argv[0]`` is an empty string (``""``).
Generic options
~~~~~~~~~~~~~~~
.. cmdoption:: -?
-h
--help
Print a short description of all command line options.
.. cmdoption:: -V
--version
Print the Python version number and exit. Example output could be::
Python 2.5.1
Miscellaneous options
~~~~~~~~~~~~~~~~~~~~~
.. cmdoption:: -d
Turn on parser debugging output (for wizards only, depending on compilation
options). See also :envvar:`PYTHONDEBUG`.
.. cmdoption:: -E
Ignore all :envvar:`PYTHON*` environment variables, e.g.
:envvar:`PYTHONPATH` and :envvar:`PYTHONHOME`, that might be set.
.. cmdoption:: -i
When a script is passed as first argument or the :option:`-c` option is used,
enter interactive mode after executing the script or the command, even when
:data:`sys.stdin` does not appear to be a terminal. The
:envvar:`PYTHONSTARTUP` file is not read.
This can be useful to inspect global variables or a stack trace when a script
raises an exception. See also :envvar:`PYTHONINSPECT`.
.. cmdoption:: -O
Turn on basic optimizations. This changes the filename extension for
compiled (:term:`bytecode`) files from ``.pyc`` to ``.pyo``. See also
:envvar:`PYTHONOPTIMIZE`.
.. cmdoption:: -OO
Discard docstrings in addition to the :option:`-O` optimizations.
.. cmdoption:: -Q <arg>
Division control. The argument must be one of the following:
``old``
division of int/int and long/long return an int or long (*default*)
``new``
new division semantics, i.e. division of int/int and long/long returns a
float
``warn``
old division semantics with a warning for int/int and long/long
``warnall``
old division semantics with a warning for all uses of the division operator
.. seealso::
:file:`Tools/scripts/fixdiv.py`
for a use of ``warnall``
:pep:`238` -- Changing the division operator
.. cmdoption:: -S
Disable the import of the module :mod:`site` and the site-dependent
manipulations of :data:`sys.path` that it entails.
.. cmdoption:: -t
Issue a warning when a source file mixes tabs and spaces for indentation in a
way that makes it depend on the worth of a tab expressed in spaces. Issue an
error when the option is given twice (:option:`-tt`).
.. cmdoption:: -u
Force stdin, stdout and stderr to be totally unbuffered. On systems where it
matters, also put stdin, stdout and stderr in binary mode.
Note that there is internal buffering in :meth:`file.readlines` and
:ref:`bltin-file-objects` (``for line in sys.stdin``) which is not influenced
by this option. To work around this, you will want to use
:meth:`file.readline` inside a ``while 1:`` loop.
See also :envvar:`PYTHONUNBUFFERED`.
.. XXX should the -U option be documented?
.. cmdoption:: -v
Print a message each time a module is initialized, showing the place
(filename or built-in module) from which it is loaded. When given twice
(:option:`-vv`), print a message for each file that is checked for when
searching for a module. Also provides information on module cleanup at exit.
See also :envvar:`PYTHONVERBOSE`.
.. cmdoption:: -W arg
Warning control. Python's warning machinery by default prints warning
messages to :data:`sys.stderr`. A typical warning message has the following
form::
file:line: category: message
By default, each warning is printed once for each source line where it
occurs. This option controls how often warnings are printed.
Multiple :option:`-W` options may be given; when a warning matches more than
one option, the action for the last matching option is performed. Invalid
:option:`-W` options are ignored (though, a warning message is printed about
invalid options when the first warning is issued).
Warnings can also be controlled from within a Python program using the
:mod:`warnings` module.
The simplest form of argument is one of the following action strings (or a
unique abbreviation):
``ignore``
Ignore all warnings.
``default``
Explicitly request the default behavior (printing each warning once per
source line).
``all``
Print a warning each time it occurs (this may generate many messages if a
warning is triggered repeatedly for the same source line, such as inside a
loop).
``module``
Print each warning only only the first time it occurs in each module.
``once``
Print each warning only the first time it occurs in the program.
``error``
Raise an exception instead of printing a warning message.
The full form of argument is::
action:message:category:module:line
Here, *action* is as explained above but only applies to messages that match
the remaining fields. Empty fields match all values; trailing empty fields
may be omitted. The *message* field matches the start of the warning message
printed; this match is case-insensitive. The *category* field matches the
warning category. This must be a class name; the match test whether the
actual warning category of the message is a subclass of the specified warning
category. The full class name must be given. The *module* field matches the
(fully-qualified) module name; this match is case-sensitive. The *line*
field matches the line number, where zero matches all line numbers and is
thus equivalent to an omitted line number.
.. seealso::
:pep:`230` -- Warning framework
.. cmdoption:: -x
Skip the first line of the source, allowing use of non-Unix forms of
``#!cmd``. This is intended for a DOS specific hack only.
.. warning:: The line numbers in error messages will be off by one!
Related files -- UNIX
---------------------
These are subject to difference depending on local installation conventions;
:envvar:`prefix` (``${prefix}``) and :envvar:`exec_prefix` (``${exec_prefix}``)
are installation-dependent and should be interpreted as for GNU software; they
may be the same.
For example, on most Linux systems, the default for both is :file:`/usr`.
+-----------------------------------------------+------------------------------------------+
| File/directory | Meaning |
+===============================================+==========================================+
| :file:`{exec_prefix}/bin/python` | Recommended location of the interpreter. |
+-----------------------------------------------+------------------------------------------+
| :file:`{prefix}/lib/python{version}`, | Recommended locations of the directories |
| :file:`{exec_prefix}/lib/python{version}` | containing the standard modules. |
+-----------------------------------------------+------------------------------------------+
| :file:`{prefix}/include/python{version}`, | Recommended locations of the directories |
| :file:`{exec_prefix}/include/python{version}` | containing the include files needed for |
| | developing Python extensions and |
| | embedding the interpreter. |
+-----------------------------------------------+------------------------------------------+
| :file:`~/.pythonrc.py` | User-specific initialization file loaded |
| | by the user module; not used by default |
| | or by most applications. |
+-----------------------------------------------+------------------------------------------+
Environment variables
---------------------
.. envvar:: PYTHONHOME
Change the location of the standard Python libraries. By default, the
libraries are searched in :file:`{prefix}/lib/python<version>` and
:file:`{exec_prefix}/lib/python<version>`, where :file:`{prefix}` and
:file:`{exec_prefix}` are installation-dependent directories, both defaulting
to :file:`/usr/local`.
When :envvar:`PYTHONHOME` is set to a single directory, its value replaces
both :file:`{prefix}` and :file:`{exec_prefix}`. To specify different values
for these, set :envvar:`PYTHONHOME` to :file:`{prefix}:{exec_prefix}``.
.. envvar:: PYTHONPATH
Augments the default search path for module files. The format is the same as
the shell's :envvar:`PATH`: one or more directory pathnames separated by
colons. Non-existent directories are silently ignored.
The default search path is installation dependent, but generally begins with
:file:`{prefix}/lib/python<version>`` (see :envvar:`PYTHONHOME` above). It
is *always* appended to :envvar:`PYTHONPATH`.
If a script argument is given, the directory containing the script is
inserted in the path in front of :envvar:`PYTHONPATH`. The search path can
be manipulated from within a Python program as the variable :data:`sys.path`.
.. envvar:: PYTHONSTARTUP
If this is the name of a readable file, the Python commands in that file are
executed before the first prompt is displayed in interactive mode. The file
is executed in the same namespace where interactive commands are executed so
that objects defined or imported in it can be used without qualification in
the interactive session. You can also change the prompts :data:`sys.ps1` and
:data:`sys.ps2` in this file.
.. envvar:: PYTHONY2K
Set this to a non-empty string to cause the :mod:`time` module to require
dates specified as strings to include 4-digit years, otherwise 2-digit years
are converted based on rules described in the :mod:`time` module
documentation.
.. envvar:: PYTHONOPTIMIZE
If this is set to a non-empty string it is equivalent to specifying the
:option:`-O` option. If set to an integer, it is equivalent to specifying
:option:`-O` multiple times.
.. envvar:: PYTHONDEBUG
If this is set to a non-empty string it is equivalent to specifying the
:option:`-d` option. If set to an integer, it is equivalent to specifying
:option:`-d` multiple times.
.. envvar:: PYTHONINSPECT
If this is set to a non-empty string it is equivalent to specifying the
:option:`-i` option.
.. envvar:: PYTHONUNBUFFERED
If this is set to a non-empty string it is equivalent to specifying the
:option:`-u` option.
.. envvar:: PYTHONVERBOSE
If this is set to a non-empty string it is equivalent to specifying the
:option:`-v` option. If set to an integer, it is equivalent to specifying
:option:`-v` multiple times.
.. envvar:: PYTHONCASEOK
If this is set, Python ignores case in :keyword:`import` statements. This
only works on Windows.

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.. _using-index:
################
Using Python
################
This part of the documentation is devoted to general information on the setup
of the Python environment on different platform, the invocation of the
interpreter and things that make working with Python easier.
.. toctree::
cmdline.rst
mac.rst

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.. _using-on-mac:
***************************
Using Python on a Macintosh
***************************
:Author: Bob Savage <bobsavage@mac.com>
Python on a Macintosh running Mac OS X is in principle very similar to Python on
any other Unix platform, but there are a number of additional features such as
the IDE and the Package Manager that are worth pointing out.
The Mac-specific modules are documented in :ref:`mac-specific-services`.
Python on Mac OS 9 or earlier can be quite different from Python on Unix or
Windows, but is beyond the scope of this manual, as that platform is no longer
supported, starting with Python 2.4. See http://www.cwi.nl/~jack/macpython for
installers for the latest 2.3 release for Mac OS 9 and related documentation.
.. _getting-osx:
Getting and Installing MacPython
================================
Mac OS X 10.4 comes with Python 2.3 pre-installed by Apple. However, you are
encouraged to install the most recent version of Python from the Python website
(http://www.python.org). A "universal binary" build of Python 2.5, which runs
natively on the Mac's new Intel and legacy PPC CPU's, is available there.
What you get after installing is a number of things:
* A :file:`MacPython 2.5` folder in your :file:`Applications` folder. In here
you find IDLE, the development environment that is a standard part of official
Python distributions; PythonLauncher, which handles double-clicking Python
scripts from the Finder; and the "Build Applet" tool, which allows you to
package Python scripts as standalone applications on your system.
* A framework :file:`/Library/Frameworks/Python.framework`, which includes the
Python executable and libraries. The installer adds this location to your shell
path. To uninstall MacPython, you can simply remove these three things. A
symlink to the Python executable is placed in /usr/local/bin/.
The Apple-provided build of Python is installed in
:file:`/System/Library/Frameworks/Python.framework` and :file:`/usr/bin/python`,
respectively. You should never modify or delete these, as they are
Apple-controlled and are used by Apple- or third-party software.
IDLE includes a help menu that allows you to access Python documentation. If you
are completely new to Python you should start reading the tutorial introduction
in that document.
If you are familiar with Python on other Unix platforms you should read the
section on running Python scripts from the Unix shell.
How to run a Python script
--------------------------
Your best way to get started with Python on Mac OS X is through the IDLE
integrated development environment, see section :ref:`ide` and use the Help menu
when the IDE is running.
If you want to run Python scripts from the Terminal window command line or from
the Finder you first need an editor to create your script. Mac OS X comes with a
number of standard Unix command line editors, :program:`vim` and
:program:`emacs` among them. If you want a more Mac-like editor,
:program:`BBEdit` or :program:`TextWrangler` from Bare Bones Software (see
http://www.barebones.com/products/bbedit/index.shtml) are good choices, as is
:program:`TextMate` (see http://macromates.com/). Other editors include
:program:`Gvim` (http://macvim.org) and :program:`Aquamacs`
(http://aquamacs.org).
To run your script from the Terminal window you must make sure that
:file:`/usr/local/bin` is in your shell search path.
To run your script from the Finder you have two options:
* Drag it to :program:`PythonLauncher`
* Select :program:`PythonLauncher` as the default application to open your
script (or any .py script) through the finder Info window and double-click it.
:program:`PythonLauncher` has various preferences to control how your script is
launched. Option-dragging allows you to change these for one invocation, or use
its Preferences menu to change things globally.
.. _osx-gui-scripts:
Running scripts with a GUI
--------------------------
With older versions of Python, there is one Mac OS X quirk that you need to be
aware of: programs that talk to the Aqua window manager (in other words,
anything that has a GUI) need to be run in a special way. Use :program:`pythonw`
instead of :program:`python` to start such scripts.
With Python 2.5, you can use either :program:`python` or :program:`pythonw`.
Configuration
-------------
Python on OS X honors all standard Unix environment variables such as
:envvar:`PYTHONPATH`, but setting these variables for programs started from the
Finder is non-standard as the Finder does not read your :file:`.profile` or
:file:`.cshrc` at startup. You need to create a file :file:`~
/.MacOSX/environment.plist`. See Apple's Technical Document QA1067 for details.
For more information on installation Python packages in MacPython, see section
:ref:`mac-package-manager`.
.. _ide:
The IDE
=======
MacPython ships with the standard IDLE development environment. A good
introduction to using IDLE can be found at http://hkn.eecs.berkeley.edu/
dyoo/python/idle_intro/index.html.
.. _mac-package-manager:
Installing Additional Python Packages
=====================================
There are several methods to install additional Python packages:
* http://pythonmac.org/packages/ contains selected compiled packages for Python
2.5, 2.4, and 2.3.
* Packages can be installed via the standard Python distutils mode (``python
setup.py install``).
* Many packages can also be installed via the :program:`setuptools` extension.
GUI Programming on the Mac
==========================
There are several options for building GUI applications on the Mac with Python.
*PyObjC* is a Python binding to Apple's Objective-C/Cocoa framework, which is
the foundation of most modern Mac development. Information on PyObjC is
available from http://pyobjc.sourceforge.net.
The standard Python GUI toolkit is :mod:`Tkinter`, based on the cross-platform
Tk toolkit (http://www.tcl.tk). An Aqua-native version of Tk is bundled with OS
X by Apple, and the latest version can be downloaded and installed from
http://www.activestate.com; it can also be built from source.
*wxPython* is another popular cross-platform GUI toolkit that runs natively on
Mac OS X. Packages and documentation are available from http://www.wxpython.org.
*PyQt* is another popular cross-platform GUI toolkit that runs natively on Mac
OS X. More information can be found at
http://www.riverbankcomputing.co.uk/pyqt/.
Distributing Python Applications on the Mac
===========================================
The "Build Applet" tool that is placed in the MacPython 2.5 folder is fine for
packaging small Python scripts on your own machine to run as a standard Mac
application. This tool, however, is not robust enough to distribute Python
applications to other users.
The standard tool for deploying standalone Python applications on the Mac is
:program:`py2app`. More information on installing and using py2app can be found
at http://undefined.org/python/#py2app.
Application Scripting
=====================
Python can also be used to script other Mac applications via Apple's Open
Scripting Architecture (OSA); see http://appscript.sourceforge.net. Appscript is
a high-level, user-friendly Apple event bridge that allows you to control
scriptable Mac OS X applications using ordinary Python scripts. Appscript makes
Python a serious alternative to Apple's own *AppleScript* language for
automating your Mac. A related package, *PyOSA*, is an OSA language component
for the Python scripting language, allowing Python code to be executed by any
OSA-enabled application (Script Editor, Mail, iTunes, etc.). PyOSA makes Python
a full peer to AppleScript.
Other Resources
===============
The MacPython mailing list is an excellent support resource for Python users and
developers on the Mac:
http://www.python.org/community/sigs/current/pythonmac-sig/
Another useful resource is the MacPython wiki:
http://wiki.python.org/moin/MacPython