mirror of
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e68d4504fd
Apart from adding a section to describe the user scheme, this changeset also does some much needed cleanup: - fixed inverted reST targets - fixed some paths - avoided duplicating the same options listing five or six times - added missing entries for C headers locations - added documentation for --install-lib - fixed a few misuses of the option role (see #9312), but not all (not worth the time, but will do it in packaging docs) - fixed some markup The paths fixes were done with an eye on the source code in the install command, so they really describe what’s actually done. The situation on Mac OS X is rather messy: the fix for #8084 touched site and sysconfig, but distutils does not use these files anymore since the Great Revert. I suspect we have a mismatched stdlib at the moment, and the fix is not even clear (see discussion on #8084).
596 lines
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ReStructuredText
596 lines
19 KiB
ReStructuredText
.. highlightlang:: none
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.. ATTENTION: You probably should update Misc/python.man, too, if you modify
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.. this file.
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.. _using-on-general:
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Command line and environment
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============================
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The CPython interpreter scans the command line and the environment for various
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settings.
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.. impl-detail::
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Other implementations' command line schemes may differ. See
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:ref:`implementations` for further resources.
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.. _using-on-cmdline:
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Command line
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------------
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When invoking Python, you may specify any of these options::
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python [-BdEiOQsStuUvVWxX3?] [-c command | -m module-name | script | - ] [args]
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The most common use case is, of course, a simple invocation of a script::
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python myscript.py
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.. _using-on-interface-options:
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Interface options
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~~~~~~~~~~~~~~~~~
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The interpreter interface resembles that of the UNIX shell, but provides some
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additional methods of invocation:
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* When called with standard input connected to a tty device, it prompts for
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commands and executes them until an EOF (an end-of-file character, you can
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produce that with *Ctrl-D* on UNIX or *Ctrl-Z, Enter* on Windows) is read.
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* When called with a file name argument or with a file as standard input, it
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reads and executes a script from that file.
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* When called with a directory name argument, it reads and executes an
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appropriately named script from that directory.
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* When called with ``-c command``, it executes the Python statement(s) given as
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*command*. Here *command* may contain multiple statements separated by
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newlines. Leading whitespace is significant in Python statements!
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* When called with ``-m module-name``, the given module is located on the
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Python module path and executed as a script.
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In non-interactive mode, the entire input is parsed before it is executed.
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An interface option terminates the list of options consumed by the interpreter,
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all consecutive arguments will end up in :data:`sys.argv` -- note that the first
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element, subscript zero (``sys.argv[0]``), is a string reflecting the program's
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source.
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.. cmdoption:: -c <command>
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Execute the Python code in *command*. *command* can be one or more
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statements separated by newlines, with significant leading whitespace as in
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normal module code.
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If this option is given, the first element of :data:`sys.argv` will be
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``"-c"`` and the current directory will be added to the start of
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:data:`sys.path` (allowing modules in that directory to be imported as top
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level modules).
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.. cmdoption:: -m <module-name>
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Search :data:`sys.path` for the named module and execute its contents as
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the :mod:`__main__` module.
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Since the argument is a *module* name, you must not give a file extension
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(``.py``). The ``module-name`` should be a valid Python module name, but
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the implementation may not always enforce this (e.g. it may allow you to
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use a name that includes a hyphen).
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Package names are also permitted. When a package name is supplied instead
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of a normal module, the interpreter will execute ``<pkg>.__main__`` as
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the main module. This behaviour is deliberately similar to the handling
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of directories and zipfiles that are passed to the interpreter as the
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script argument.
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.. note::
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This option cannot be used with built-in modules and extension modules
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written in C, since they do not have Python module files. However, it
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can still be used for precompiled modules, even if the original source
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file is not available.
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If this option is given, the first element of :data:`sys.argv` will be the
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full path to the module file. As with the :option:`-c` option, the current
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directory will be added to the start of :data:`sys.path`.
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Many standard library modules contain code that is invoked on their execution
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as a script. An example is the :mod:`timeit` module::
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python -mtimeit -s 'setup here' 'benchmarked code here'
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python -mtimeit -h # for details
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.. seealso::
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:func:`runpy.run_module`
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Equivalent functionality directly available to Python code
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:pep:`338` -- Executing modules as scripts
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.. versionadded:: 2.4
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.. versionchanged:: 2.5
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The named module can now be located inside a package.
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.. versionchanged:: 2.7
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Supply the package name to run a ``__main__`` submodule.
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sys.argv[0] is now set to ``"-m"`` while searching for the module
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(it was previously incorrectly set to ``"-c"``)
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.. describe:: -
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Read commands from standard input (:data:`sys.stdin`). If standard input is
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a terminal, :option:`-i` is implied.
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If this option is given, the first element of :data:`sys.argv` will be
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``"-"`` and the current directory will be added to the start of
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:data:`sys.path`.
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.. describe:: <script>
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Execute the Python code contained in *script*, which must be a filesystem
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path (absolute or relative) referring to either a Python file, a directory
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containing a ``__main__.py`` file, or a zipfile containing a
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``__main__.py`` file.
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If this option is given, the first element of :data:`sys.argv` will be the
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script name as given on the command line.
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If the script name refers directly to a Python file, the directory
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containing that file is added to the start of :data:`sys.path`, and the
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file is executed as the :mod:`__main__` module.
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If the script name refers to a directory or zipfile, the script name is
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added to the start of :data:`sys.path` and the ``__main__.py`` file in
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that location is executed as the :mod:`__main__` module.
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.. versionchanged:: 2.5
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Directories and zipfiles containing a ``__main__.py`` file at the top
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level are now considered valid Python scripts.
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If no interface option is given, :option:`-i` is implied, ``sys.argv[0]`` is
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an empty string (``""``) and the current directory will be added to the
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start of :data:`sys.path`.
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.. seealso:: :ref:`tut-invoking`
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Generic options
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~~~~~~~~~~~~~~~
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.. cmdoption:: -?
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-h
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--help
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Print a short description of all command line options.
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.. versionchanged:: 2.5
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The ``--help`` variant.
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.. cmdoption:: -V
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--version
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Print the Python version number and exit. Example output could be::
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Python 2.5.1
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.. versionchanged:: 2.5
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The ``--version`` variant.
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Miscellaneous options
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~~~~~~~~~~~~~~~~~~~~~
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.. cmdoption:: -B
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If given, Python won't try to write ``.pyc`` or ``.pyo`` files on the
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import of source modules. See also :envvar:`PYTHONDONTWRITEBYTECODE`.
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.. versionadded:: 2.6
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.. cmdoption:: -d
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Turn on parser debugging output (for wizards only, depending on compilation
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options). See also :envvar:`PYTHONDEBUG`.
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.. cmdoption:: -E
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Ignore all :envvar:`PYTHON*` environment variables, e.g.
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:envvar:`PYTHONPATH` and :envvar:`PYTHONHOME`, that might be set.
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.. versionadded:: 2.2
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.. cmdoption:: -i
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When a script is passed as first argument or the :option:`-c` option is used,
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enter interactive mode after executing the script or the command, even when
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:data:`sys.stdin` does not appear to be a terminal. The
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:envvar:`PYTHONSTARTUP` file is not read.
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This can be useful to inspect global variables or a stack trace when a script
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raises an exception. See also :envvar:`PYTHONINSPECT`.
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.. cmdoption:: -O
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Turn on basic optimizations. This changes the filename extension for
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compiled (:term:`bytecode`) files from ``.pyc`` to ``.pyo``. See also
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:envvar:`PYTHONOPTIMIZE`.
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.. cmdoption:: -OO
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Discard docstrings in addition to the :option:`-O` optimizations.
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.. cmdoption:: -Q <arg>
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Division control. The argument must be one of the following:
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``old``
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division of int/int and long/long return an int or long (*default*)
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``new``
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new division semantics, i.e. division of int/int and long/long returns a
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float
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``warn``
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old division semantics with a warning for int/int and long/long
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``warnall``
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old division semantics with a warning for all uses of the division operator
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.. seealso::
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:file:`Tools/scripts/fixdiv.py`
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for a use of ``warnall``
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:pep:`238` -- Changing the division operator
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.. cmdoption:: -s
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Don't add the :data:`user site-packages directory <site.USER_SITE>` to
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:data:`sys.path`.
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.. versionadded:: 2.6
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.. seealso::
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:pep:`370` -- Per user site-packages directory
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.. cmdoption:: -S
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Disable the import of the module :mod:`site` and the site-dependent
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manipulations of :data:`sys.path` that it entails.
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.. cmdoption:: -t
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Issue a warning when a source file mixes tabs and spaces for indentation in a
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way that makes it depend on the worth of a tab expressed in spaces. Issue an
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error when the option is given twice (:option:`-tt`).
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.. cmdoption:: -u
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Force stdin, stdout and stderr to be totally unbuffered. On systems where it
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matters, also put stdin, stdout and stderr in binary mode.
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Note that there is internal buffering in :meth:`file.readlines` and
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:ref:`bltin-file-objects` (``for line in sys.stdin``) which is not influenced
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by this option. To work around this, you will want to use
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:meth:`file.readline` inside a ``while 1:`` loop.
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See also :envvar:`PYTHONUNBUFFERED`.
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.. cmdoption:: -v
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Print a message each time a module is initialized, showing the place
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(filename or built-in module) from which it is loaded. When given twice
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(:option:`-vv`), print a message for each file that is checked for when
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searching for a module. Also provides information on module cleanup at exit.
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See also :envvar:`PYTHONVERBOSE`.
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.. cmdoption:: -W arg
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Warning control. Python's warning machinery by default prints warning
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messages to :data:`sys.stderr`. A typical warning message has the following
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form::
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file:line: category: message
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By default, each warning is printed once for each source line where it
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occurs. This option controls how often warnings are printed.
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Multiple :option:`-W` options may be given; when a warning matches more than
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one option, the action for the last matching option is performed. Invalid
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:option:`-W` options are ignored (though, a warning message is printed about
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invalid options when the first warning is issued).
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Starting from Python 2.7, :exc:`DeprecationWarning` and its descendants
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are ignored by default. The :option:`-Wd` option can be used to re-enable
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them.
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Warnings can also be controlled from within a Python program using the
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:mod:`warnings` module.
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The simplest form of argument is one of the following action strings (or a
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unique abbreviation) by themselves:
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``ignore``
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Ignore all warnings.
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``default``
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Explicitly request the default behavior (printing each warning once per
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source line).
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``all``
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Print a warning each time it occurs (this may generate many messages if a
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warning is triggered repeatedly for the same source line, such as inside a
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loop).
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``module``
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Print each warning only the first time it occurs in each module.
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``once``
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Print each warning only the first time it occurs in the program.
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``error``
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Raise an exception instead of printing a warning message.
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The full form of argument is::
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action:message:category:module:line
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Here, *action* is as explained above but only applies to messages that match
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the remaining fields. Empty fields match all values; trailing empty fields
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may be omitted. The *message* field matches the start of the warning message
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printed; this match is case-insensitive. The *category* field matches the
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warning category. This must be a class name; the match tests whether the
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actual warning category of the message is a subclass of the specified warning
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category. The full class name must be given. The *module* field matches the
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(fully-qualified) module name; this match is case-sensitive. The *line*
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field matches the line number, where zero matches all line numbers and is
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thus equivalent to an omitted line number.
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.. seealso::
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:mod:`warnings` -- the warnings module
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:pep:`230` -- Warning framework
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:envvar:`PYTHONWARNINGS`
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.. cmdoption:: -x
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Skip the first line of the source, allowing use of non-Unix forms of
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``#!cmd``. This is intended for a DOS specific hack only.
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.. note:: The line numbers in error messages will be off by one.
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.. cmdoption:: -3
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Warn about Python 3.x incompatibilities which cannot be fixed trivially by
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:ref:`2to3 <2to3-reference>`. Among these are:
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* :meth:`dict.has_key`
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* :func:`apply`
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* :func:`callable`
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* :func:`coerce`
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* :func:`execfile`
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* :func:`reduce`
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* :func:`reload`
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Using these will emit a :exc:`DeprecationWarning`.
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.. versionadded:: 2.6
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Options you shouldn't use
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~~~~~~~~~~~~~~~~~~~~~~~~~
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.. cmdoption:: -J
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Reserved for use by Jython_.
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.. _Jython: http://jython.org
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.. cmdoption:: -U
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Turns all string literals into unicodes globally. Do not be tempted to use
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this option as it will probably break your world. It also produces
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``.pyc`` files with a different magic number than normal. Instead, you can
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enable unicode literals on a per-module basis by using::
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from __future__ import unicode_literals
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at the top of the file. See :mod:`__future__` for details.
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.. cmdoption:: -X
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Reserved for alternative implementations of Python to use for their own
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purposes.
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.. _using-on-envvars:
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Environment variables
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---------------------
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These environment variables influence Python's behavior.
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.. envvar:: PYTHONHOME
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Change the location of the standard Python libraries. By default, the
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libraries are searched in :file:`{prefix}/lib/python{version}` and
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:file:`{exec_prefix}/lib/python{version}`, where :file:`{prefix}` and
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:file:`{exec_prefix}` are installation-dependent directories, both defaulting
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to :file:`/usr/local`.
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When :envvar:`PYTHONHOME` is set to a single directory, its value replaces
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both :file:`{prefix}` and :file:`{exec_prefix}`. To specify different values
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for these, set :envvar:`PYTHONHOME` to :file:`{prefix}:{exec_prefix}`.
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.. envvar:: PYTHONPATH
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Augment the default search path for module files. The format is the same as
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the shell's :envvar:`PATH`: one or more directory pathnames separated by
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:data:`os.pathsep` (e.g. colons on Unix or semicolons on Windows).
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Non-existent directories are silently ignored.
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In addition to normal directories, individual :envvar:`PYTHONPATH` entries
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may refer to zipfiles containing pure Python modules (in either source or
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compiled form). Extension modules cannot be imported from zipfiles.
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The default search path is installation dependent, but generally begins with
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:file:`{prefix}/lib/python{version}` (see :envvar:`PYTHONHOME` above). It
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is *always* appended to :envvar:`PYTHONPATH`.
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An additional directory will be inserted in the search path in front of
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:envvar:`PYTHONPATH` as described above under
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:ref:`using-on-interface-options`. The search path can be manipulated from
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within a Python program as the variable :data:`sys.path`.
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.. envvar:: PYTHONSTARTUP
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If this is the name of a readable file, the Python commands in that file are
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executed before the first prompt is displayed in interactive mode. The file
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is executed in the same namespace where interactive commands are executed so
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that objects defined or imported in it can be used without qualification in
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the interactive session. You can also change the prompts :data:`sys.ps1` and
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:data:`sys.ps2` in this file.
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.. envvar:: PYTHONY2K
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Set this to a non-empty string to cause the :mod:`time` module to require
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dates specified as strings to include 4-digit years, otherwise 2-digit years
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are converted based on rules described in the :mod:`time` module
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documentation.
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.. envvar:: PYTHONOPTIMIZE
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If this is set to a non-empty string it is equivalent to specifying the
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:option:`-O` option. If set to an integer, it is equivalent to specifying
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:option:`-O` multiple times.
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.. envvar:: PYTHONDEBUG
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If this is set to a non-empty string it is equivalent to specifying the
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:option:`-d` option. If set to an integer, it is equivalent to specifying
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:option:`-d` multiple times.
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.. envvar:: PYTHONINSPECT
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If this is set to a non-empty string it is equivalent to specifying the
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:option:`-i` option.
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This variable can also be modified by Python code using :data:`os.environ`
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to force inspect mode on program termination.
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.. envvar:: PYTHONUNBUFFERED
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If this is set to a non-empty string it is equivalent to specifying the
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:option:`-u` option.
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.. envvar:: PYTHONVERBOSE
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If this is set to a non-empty string it is equivalent to specifying the
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:option:`-v` option. If set to an integer, it is equivalent to specifying
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:option:`-v` multiple times.
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.. envvar:: PYTHONCASEOK
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If this is set, Python ignores case in :keyword:`import` statements. This
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only works on Windows.
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.. envvar:: PYTHONDONTWRITEBYTECODE
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If this is set, Python won't try to write ``.pyc`` or ``.pyo`` files on the
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import of source modules.
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.. versionadded:: 2.6
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.. envvar:: PYTHONIOENCODING
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Overrides the encoding used for stdin/stdout/stderr, in the syntax
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``encodingname:errorhandler``. The ``:errorhandler`` part is optional and
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has the same meaning as in :func:`str.encode`.
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.. versionadded:: 2.6
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.. envvar:: PYTHONNOUSERSITE
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If this is set, Python won't add the :data:`user site-packages directory
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<site.USER_SITE>` to :data:`sys.path`.
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.. versionadded:: 2.6
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.. seealso::
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:pep:`370` -- Per user site-packages directory
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.. envvar:: PYTHONUSERBASE
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Defines the :data:`user base directory <site.USER_BASE>`, which is used to
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compute the path of the :data:`user site-packages directory <site.USER_SITE>`
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and :ref:`Distutils installation paths <inst-alt-install-user>` for ``python
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setup.py install --user``.
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.. versionadded:: 2.6
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.. seealso::
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:pep:`370` -- Per user site-packages directory
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.. envvar:: PYTHONEXECUTABLE
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If this environment variable is set, ``sys.argv[0]`` will be set to its
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value instead of the value got through the C runtime. Only works on
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Mac OS X.
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.. envvar:: PYTHONWARNINGS
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This is equivalent to the :option:`-W` option. If set to a comma
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separated string, it is equivalent to specifying :option:`-W` multiple
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times.
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Debug-mode variables
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~~~~~~~~~~~~~~~~~~~~
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Setting these variables only has an effect in a debug build of Python, that is,
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if Python was configured with the ``--with-pydebug`` build option.
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.. envvar:: PYTHONTHREADDEBUG
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If set, Python will print threading debug info.
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.. versionchanged:: 2.6
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Previously, this variable was called ``THREADDEBUG``.
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.. envvar:: PYTHONDUMPREFS
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If set, Python will dump objects and reference counts still alive after
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shutting down the interpreter.
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.. envvar:: PYTHONMALLOCSTATS
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If set, Python will print memory allocation statistics every time a new
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object arena is created, and on shutdown.
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