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:mod:`sysconfig` --- Provide access to Python's configuration information
=========================================================================
.. module:: sysconfig
:synopsis: Python's configuration information
.. moduleauthor:: Tarek Ziade <tarek@ziade.org>
.. sectionauthor:: Tarek Ziade <tarek@ziade.org>
.. index::
single: configuration information
.. versionadded:: 2.7
**Source code:** :source:`Lib/sysconfig.py`
--------------
The :mod:`sysconfig` module provides access to Python's configuration
information like the list of installation paths and the configuration variables
relevant for the current platform.
Configuration variables
-----------------------
A Python distribution contains a :file:`Makefile` and a :file:`pyconfig.h`
header file that are necessary to build both the Python binary itself and
third-party C extensions compiled using :mod:`distutils`.
:mod:`sysconfig` puts all variables found in these files in a dictionary that
can be accessed using :func:`get_config_vars` or :func:`get_config_var`.
Notice that on Windows, it's a much smaller set.
.. function:: get_config_vars(\*args)
With no arguments, return a dictionary of all configuration variables
relevant for the current platform.
With arguments, return a list of values that result from looking up each
argument in the configuration variable dictionary.
For each argument, if the value is not found, return ``None``.
.. function:: get_config_var(name)
Return the value of a single variable *name*. Equivalent to
``get_config_vars().get(name)``.
If *name* is not found, return ``None``.
Example of usage::
>>> import sysconfig
>>> sysconfig.get_config_var('Py_ENABLE_SHARED')
0
>>> sysconfig.get_config_var('LIBDIR')
'/usr/local/lib'
>>> sysconfig.get_config_vars('AR', 'CXX')
['ar', 'g++']
Installation paths
------------------
Python uses an installation scheme that differs depending on the platform and on
the installation options. These schemes are stored in :mod:`sysconfig` under
unique identifiers based on the value returned by :const:`os.name`.
Every new component that is installed using :mod:`distutils` or a
Distutils-based system will follow the same scheme to copy its file in the right
places.
Python currently supports seven schemes:
- *posix_prefix*: scheme for Posix platforms like Linux or Mac OS X. This is
the default scheme used when Python or a component is installed.
- *posix_home*: scheme for Posix platforms used when a *home* option is used
upon installation. This scheme is used when a component is installed through
Distutils with a specific home prefix.
- *posix_user*: scheme for Posix platforms used when a component is installed
through Distutils and the *user* option is used. This scheme defines paths
located under the user home directory.
- *nt*: scheme for NT platforms like Windows.
- *nt_user*: scheme for NT platforms, when the *user* option is used.
- *os2*: scheme for OS/2 platforms.
- *os2_home*: scheme for OS/2 patforms, when the *user* option is used.
Each scheme is itself composed of a series of paths and each path has a unique
identifier. Python currently uses eight paths:
- *stdlib*: directory containing the standard Python library files that are not
platform-specific.
- *platstdlib*: directory containing the standard Python library files that are
platform-specific.
- *platlib*: directory for site-specific, platform-specific files.
- *purelib*: directory for site-specific, non-platform-specific files.
- *include*: directory for non-platform-specific header files.
- *platinclude*: directory for platform-specific header files.
- *scripts*: directory for script files.
- *data*: directory for data files.
:mod:`sysconfig` provides some functions to determine these paths.
.. function:: get_scheme_names()
Return a tuple containing all schemes currently supported in
:mod:`sysconfig`.
.. function:: get_path_names()
Return a tuple containing all path names currently supported in
:mod:`sysconfig`.
.. function:: get_path(name, [scheme, [vars, [expand]]])
Return an installation path corresponding to the path *name*, from the
install scheme named *scheme*.
*name* has to be a value from the list returned by :func:`get_path_names`.
:mod:`sysconfig` stores installation paths corresponding to each path name,
for each platform, with variables to be expanded. For instance the *stdlib*
path for the *nt* scheme is: ``{base}/Lib``.
:func:`get_path` will use the variables returned by :func:`get_config_vars`
to expand the path. All variables have default values for each platform so
one may call this function and get the default value.
If *scheme* is provided, it must be a value from the list returned by
:func:`get_scheme_names`. Otherwise, the default scheme for the current
platform is used.
If *vars* is provided, it must be a dictionary of variables that will update
the dictionary return by :func:`get_config_vars`.
If *expand* is set to ``False``, the path will not be expanded using the
variables.
If *name* is not found, return ``None``.
.. function:: get_paths([scheme, [vars, [expand]]])
Return a dictionary containing all installation paths corresponding to an
installation scheme. See :func:`get_path` for more information.
If *scheme* is not provided, will use the default scheme for the current
platform.
If *vars* is provided, it must be a dictionary of variables that will
update the dictionary used to expand the paths.
If *expand* is set to false, the paths will not be expanded.
If *scheme* is not an existing scheme, :func:`get_paths` will raise a
:exc:`KeyError`.
Other functions
---------------
.. function:: get_python_version()
Return the ``MAJOR.MINOR`` Python version number as a string. Similar to
``sys.version[:3]``.
.. function:: get_platform()
Return a string that identifies the current platform.
This is used mainly to distinguish platform-specific build directories and
platform-specific built distributions. Typically includes the OS name and
version and the architecture (as supplied by :func:`os.uname`), although the
exact information included depends on the OS; e.g. for IRIX the architecture
isn't particularly important (IRIX only runs on SGI hardware), but for Linux
the kernel version isn't particularly important.
Examples of returned values:
- linux-i586
- linux-alpha (?)
- solaris-2.6-sun4u
- irix-5.3
- irix64-6.2
Windows will return one of:
- win-amd64 (64bit Windows on AMD64 (aka x86_64, Intel64, EM64T, etc)
- win-ia64 (64bit Windows on Itanium)
- win32 (all others - specifically, sys.platform is returned)
Mac OS X can return:
- macosx-10.6-ppc
- macosx-10.4-ppc64
- macosx-10.3-i386
- macosx-10.4-fat
For other non-POSIX platforms, currently just returns :data:`sys.platform`.
.. function:: is_python_build()
Return ``True`` if the current Python installation was built from source.
.. function:: parse_config_h(fp[, vars])
Parse a :file:`config.h`\-style file.
*fp* is a file-like object pointing to the :file:`config.h`\-like file.
A dictionary containing name/value pairs is returned. If an optional
dictionary is passed in as the second argument, it is used instead of a new
dictionary, and updated with the values read in the file.
.. function:: get_config_h_filename()
Return the path of :file:`pyconfig.h`.
.. function:: get_makefile_filename()
Return the path of :file:`Makefile`.
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