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259 lines
8.4 KiB
259 lines
8.4 KiB
:mod:`sysconfig` --- Provide access to Python's configuration information
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=========================================================================
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.. module:: sysconfig
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:synopsis: Python's configuration information
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.. moduleauthor:: Tarek Ziadé <tarek@ziade.org>
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.. sectionauthor:: Tarek Ziadé <tarek@ziade.org>
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.. versionadded:: 3.2
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**Source code:** :source:`Lib/sysconfig.py`
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.. index::
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single: configuration information
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--------------
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The :mod:`sysconfig` module provides access to Python's configuration
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information like the list of installation paths and the configuration variables
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relevant for the current platform.
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Configuration variables
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-----------------------
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A Python distribution contains a :file:`Makefile` and a :file:`pyconfig.h`
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header file that are necessary to build both the Python binary itself and
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third-party C extensions compiled using :mod:`distutils`.
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:mod:`sysconfig` puts all variables found in these files in a dictionary that
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can be accessed using :func:`get_config_vars` or :func:`get_config_var`.
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Notice that on Windows, it's a much smaller set.
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.. function:: get_config_vars(\*args)
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With no arguments, return a dictionary of all configuration variables
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relevant for the current platform.
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With arguments, return a list of values that result from looking up each
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argument in the configuration variable dictionary.
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For each argument, if the value is not found, return ``None``.
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.. function:: get_config_var(name)
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Return the value of a single variable *name*. Equivalent to
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``get_config_vars().get(name)``.
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If *name* is not found, return ``None``.
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Example of usage::
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>>> import sysconfig
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>>> sysconfig.get_config_var('Py_ENABLE_SHARED')
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0
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>>> sysconfig.get_config_var('LIBDIR')
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'/usr/local/lib'
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>>> sysconfig.get_config_vars('AR', 'CXX')
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['ar', 'g++']
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Installation paths
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------------------
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Python uses an installation scheme that differs depending on the platform and on
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the installation options. These schemes are stored in :mod:`sysconfig` under
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unique identifiers based on the value returned by :const:`os.name`.
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Every new component that is installed using :mod:`distutils` or a
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Distutils-based system will follow the same scheme to copy its file in the right
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places.
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Python currently supports seven schemes:
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- *posix_prefix*: scheme for POSIX platforms like Linux or Mac OS X. This is
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the default scheme used when Python or a component is installed.
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- *posix_home*: scheme for POSIX platforms used when a *home* option is used
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upon installation. This scheme is used when a component is installed through
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Distutils with a specific home prefix.
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- *posix_user*: scheme for POSIX platforms used when a component is installed
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through Distutils and the *user* option is used. This scheme defines paths
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located under the user home directory.
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- *nt*: scheme for NT platforms like Windows.
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- *nt_user*: scheme for NT platforms, when the *user* option is used.
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Each scheme is itself composed of a series of paths and each path has a unique
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identifier. Python currently uses eight paths:
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- *stdlib*: directory containing the standard Python library files that are not
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platform-specific.
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- *platstdlib*: directory containing the standard Python library files that are
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platform-specific.
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- *platlib*: directory for site-specific, platform-specific files.
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- *purelib*: directory for site-specific, non-platform-specific files.
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- *include*: directory for non-platform-specific header files.
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- *platinclude*: directory for platform-specific header files.
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- *scripts*: directory for script files.
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- *data*: directory for data files.
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:mod:`sysconfig` provides some functions to determine these paths.
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.. function:: get_scheme_names()
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Return a tuple containing all schemes currently supported in
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:mod:`sysconfig`.
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.. function:: get_path_names()
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Return a tuple containing all path names currently supported in
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:mod:`sysconfig`.
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.. function:: get_path(name, [scheme, [vars, [expand]]])
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Return an installation path corresponding to the path *name*, from the
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install scheme named *scheme*.
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*name* has to be a value from the list returned by :func:`get_path_names`.
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:mod:`sysconfig` stores installation paths corresponding to each path name,
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for each platform, with variables to be expanded. For instance the *stdlib*
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path for the *nt* scheme is: ``{base}/Lib``.
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:func:`get_path` will use the variables returned by :func:`get_config_vars`
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to expand the path. All variables have default values for each platform so
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one may call this function and get the default value.
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If *scheme* is provided, it must be a value from the list returned by
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:func:`get_scheme_names`. Otherwise, the default scheme for the current
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platform is used.
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If *vars* is provided, it must be a dictionary of variables that will update
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the dictionary return by :func:`get_config_vars`.
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If *expand* is set to ``False``, the path will not be expanded using the
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variables.
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If *name* is not found, return ``None``.
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.. function:: get_paths([scheme, [vars, [expand]]])
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Return a dictionary containing all installation paths corresponding to an
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installation scheme. See :func:`get_path` for more information.
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If *scheme* is not provided, will use the default scheme for the current
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platform.
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If *vars* is provided, it must be a dictionary of variables that will
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update the dictionary used to expand the paths.
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If *expand* is set to false, the paths will not be expanded.
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If *scheme* is not an existing scheme, :func:`get_paths` will raise a
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:exc:`KeyError`.
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Other functions
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---------------
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.. function:: get_python_version()
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Return the ``MAJOR.MINOR`` Python version number as a string. Similar to
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``'%d.%d' % sys.version_info[:2]``.
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.. function:: get_platform()
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Return a string that identifies the current platform.
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This is used mainly to distinguish platform-specific build directories and
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platform-specific built distributions. Typically includes the OS name and
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version and the architecture (as supplied by 'os.uname()'), although the
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exact information included depends on the OS; e.g., on Linux, the kernel
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version isn't particularly important.
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Examples of returned values:
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- linux-i586
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- linux-alpha (?)
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- solaris-2.6-sun4u
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Windows will return one of:
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- win-amd64 (64bit Windows on AMD64, aka x86_64, Intel64, and EM64T)
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- win32 (all others - specifically, sys.platform is returned)
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Mac OS X can return:
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- macosx-10.6-ppc
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- macosx-10.4-ppc64
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- macosx-10.3-i386
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- macosx-10.4-fat
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For other non-POSIX platforms, currently just returns :data:`sys.platform`.
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.. function:: is_python_build()
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Return ``True`` if the running Python interpreter was built from source and
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is being run from its built location, and not from a location resulting from
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e.g. running ``make install`` or installing via a binary installer.
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.. function:: parse_config_h(fp[, vars])
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Parse a :file:`config.h`\-style file.
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*fp* is a file-like object pointing to the :file:`config.h`\-like file.
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A dictionary containing name/value pairs is returned. If an optional
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dictionary is passed in as the second argument, it is used instead of a new
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dictionary, and updated with the values read in the file.
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.. function:: get_config_h_filename()
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Return the path of :file:`pyconfig.h`.
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.. function:: get_makefile_filename()
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Return the path of :file:`Makefile`.
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Using :mod:`sysconfig` as a script
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----------------------------------
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You can use :mod:`sysconfig` as a script with Python's *-m* option:
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.. code-block:: shell-session
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$ python -m sysconfig
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Platform: "macosx-10.4-i386"
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Python version: "3.2"
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Current installation scheme: "posix_prefix"
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Paths:
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data = "/usr/local"
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include = "/Users/tarek/Dev/svn.python.org/py3k/Include"
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platinclude = "."
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platlib = "/usr/local/lib/python3.2/site-packages"
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platstdlib = "/usr/local/lib/python3.2"
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purelib = "/usr/local/lib/python3.2/site-packages"
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scripts = "/usr/local/bin"
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stdlib = "/usr/local/lib/python3.2"
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Variables:
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AC_APPLE_UNIVERSAL_BUILD = "0"
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AIX_GENUINE_CPLUSPLUS = "0"
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AR = "ar"
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ARFLAGS = "rc"
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...
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This call will print in the standard output the information returned by
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:func:`get_platform`, :func:`get_python_version`, :func:`get_path` and
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:func:`get_config_vars`.
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