29.2.1.Configuration variables¶

A Python distribution contains aMakefile and apyconfig.hheader file that are necessary to build both the Python binary itself andthird-party C extensions compiled usingdistutils.

sysconfig puts all variables found in these files in a dictionary thatcan be accessed usingget_config_vars() orget_config_var().

Notice that on Windows, it’s a much smaller set.

sysconfig.get_config_vars(*args)¶

With no arguments, return a dictionary of all configuration variablesrelevant for the current platform.

With arguments, return a list of values that result from looking up eachargument in the configuration variable dictionary.

For each argument, if the value is not found, returnNone.

sysconfig.get_config_var(name)¶

Return the value of a single variablename. Equivalent toget_config_vars().get(name).

Ifname is not found, returnNone.

Example of usage:

>>>importsysconfig>>>sysconfig.get_config_var('Py_ENABLE_SHARED')0>>>sysconfig.get_config_var('LIBDIR')'/usr/local/lib'>>>sysconfig.get_config_vars('AR','CXX')['ar', 'g++']

29.2.2.Installation paths¶

Python uses an installation scheme that differs depending on the platform and onthe installation options. These schemes are stored insysconfig underunique identifiers based on the value returned byos.name.

Every new component that is installed usingdistutils or aDistutils-based system will follow the same scheme to copy its file in the rightplaces.

Python currently supports seven schemes:

• posix_prefix: scheme for Posix platforms like Linux or Mac OS X. This isthe default scheme used when Python or a component is installed.

• posix_home: scheme for Posix platforms used when ahome option is usedupon installation. This scheme is used when a component is installed throughDistutils with a specific home prefix.

• posix_user: scheme for Posix platforms used when a component is installedthrough Distutils and theuser option is used. This scheme defines pathslocated under the user home directory.

• nt: scheme for NT platforms like Windows.

• nt_user: scheme for NT platforms, when theuser option is used.

Each scheme is itself composed of a series of paths and each path has a uniqueidentifier. Python currently uses eight paths:

• stdlib: directory containing the standard Python library files that are notplatform-specific.

• platstdlib: directory containing the standard Python library files that areplatform-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.

sysconfig provides some functions to determine these paths.

sysconfig.get_scheme_names()¶

Return a tuple containing all schemes currently supported insysconfig.

sysconfig.get_path_names()¶

Return a tuple containing all path names currently supported insysconfig.

sysconfig.get_path(name[,scheme[,vars[,expand]]])¶

Return an installation path corresponding to the pathname, from theinstall scheme namedscheme.

name has to be a value from the list returned byget_path_names().

sysconfig stores installation paths corresponding to each path name,for each platform, with variables to be expanded. For instance thestdlibpath for thent scheme is:{base}/Lib.

get_path() will use the variables returned byget_config_vars()to expand the path. All variables have default values for each platform soone may call this function and get the default value.

Ifscheme is provided, it must be a value from the list returned byget_scheme_names(). Otherwise, the default scheme for the currentplatform is used.

Ifvars is provided, it must be a dictionary of variables that will updatethe dictionary return byget_config_vars().

Ifexpand is set toFalse, the path will not be expanded using thevariables.

Ifname is not found, returnNone.

sysconfig.get_paths([scheme[,vars[,expand]]])¶

Return a dictionary containing all installation paths corresponding to aninstallation scheme. Seeget_path() for more information.

Ifscheme is not provided, will use the default scheme for the currentplatform.

Ifvars is provided, it must be a dictionary of variables that willupdate the dictionary used to expand the paths.

Ifexpand is set to false, the paths will not be expanded.

Ifscheme is not an existing scheme,get_paths() will raise aKeyError.

29.2.3.Other functions¶

sysconfig.get_python_version()¶

Return theMAJOR.MINOR Python version number as a string. Similar to'%d.%d'%sys.version_info[:2].

sysconfig.get_platform()¶

Return a string that identifies the current platform.

This is used mainly to distinguish platform-specific build directories andplatform-specific built distributions. Typically includes the OS name andversion and the architecture (as supplied byos.uname()), although theexact information included depends on the OS; e.g. for IRIX the architectureisn’t particularly important (IRIX only runs on SGI hardware), but for Linuxthe 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, and EM64T)

• 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 returnssys.platform.

sysconfig.is_python_build()¶

ReturnTrue if the running Python interpreter was built from source andis being run from its built location, and not from a location resulting frome.g. runningmakeinstall or installing via a binary installer.

sysconfig.parse_config_h(fp[,vars])¶

Parse aconfig.h-style file.

fp is a file-like object pointing to theconfig.h-like file.

A dictionary containing name/value pairs is returned. If an optionaldictionary is passed in as the second argument, it is used instead of a newdictionary, and updated with the values read in the file.

sysconfig.get_config_h_filename()¶

Return the path ofpyconfig.h.

sysconfig.get_makefile_filename()¶

Return the path ofMakefile.

29.2.4.Usingsysconfig as a script¶

You can usesysconfig as a script with Python’s-m option:

$python-msysconfigPlatform: "macosx-10.4-i386"Python version: "3.2"Current installation scheme: "posix_prefix"Paths:        data = "/usr/local"        include = "/Users/tarek/Dev/svn.python.org/py3k/Include"        platinclude = "."        platlib = "/usr/local/lib/python3.2/site-packages"        platstdlib = "/usr/local/lib/python3.2"        purelib = "/usr/local/lib/python3.2/site-packages"        scripts = "/usr/local/bin"        stdlib = "/usr/local/lib/python3.2"Variables:        AC_APPLE_UNIVERSAL_BUILD = "0"        AIX_GENUINE_CPLUSPLUS = "0"        AR = "ar"        ARFLAGS = "rc"        ...

This call will print in the standard output the information returned byget_platform(),get_python_version(),get_path() andget_config_vars().