sysconfig — Provide access to Python’s configuration information (original) (raw)

Added in version 3.2.

Source code: Lib/sysconfig

The 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 Makefile and a pyconfig.hheader file that are necessary to build both the Python binary itself and third-party C extensions compiled using setuptools.

sysconfig puts all variables found in these files in a dictionary that can be accessed using get_config_vars() or get_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 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.

sysconfig.get_config_var(name)¶

Return the value of a single variable name. Equivalent toget_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 sysconfig under unique identifiers based on the value returned by os.name. The schemes are used by package installers to determine where to copy files to.

Python currently supports nine schemes:

• posix_prefix: scheme for POSIX platforms like Linux or macOS. This is the default scheme used when Python or a component is installed.
• posix_home: scheme for POSIX platforms, when the home option is used. This scheme defines paths located under a specific home prefix.
• posix_user: scheme for POSIX platforms, when the user option is used. This scheme defines paths located under the user’s home directory (site.USER_BASE).
• posix_venv: scheme for Python virtual environments on POSIX platforms; by default it is the same as posix_prefix.
• nt: scheme for Windows. This is the default scheme used when Python or a component is installed.
• nt_user: scheme for Windows, when the user option is used.
• nt_venv: scheme for Python virtual environments on Windows; by default it is the same as nt.
• venv: a scheme with values from either posix_venv or nt_venv depending on the platform Python runs on.
• osx_framework_user: scheme for macOS, 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 (‘pure’ Python).
• include: directory for non-platform-specific header files for the Python C-API.
• platinclude: directory for platform-specific header files for the Python C-API.
• scripts: directory for script files.
• data: directory for data files.

User scheme¶

This scheme is designed to be the most convenient solution for users that don’t have write permission to the global site-packages directory or don’t want to install into it.

Files will be installed into subdirectories of site.USER_BASE (written as _userbase_ hereafter). This scheme installs pure Python modules and extension modules in the same location (also known as site.USER_SITE).

posix_user¶

nt_user¶

osx_framework_user¶

Home scheme¶

The idea behind the “home scheme” is that you build and maintain a personal stash of Python modules. This scheme’s name is derived from the idea of a “home” directory on Unix, since it’s not unusual for a Unix user to make their home directory have a layout similar to /usr/ or /usr/local/. This scheme can be used by anyone, regardless of the operating system they are installing for.

posix_home¶

Prefix scheme¶

The “prefix scheme” is useful when you wish to use one Python installation to perform the build/install (i.e., to run the setup script), but install modules into the third-party module directory of a different Python installation (or something that looks like a different Python installation). If this sounds a trifle unusual, it is—that’s why the user and home schemes come before. However, there are at least two known cases where the prefix scheme will be useful.

First, consider that many Linux distributions put Python in /usr, rather than the more traditional /usr/local. This is entirely appropriate, since in those cases Python is part of “the system” rather than a local add-on. However, if you are installing Python modules from source, you probably want them to go in /usr/local/lib/python2._X_ rather than/usr/lib/python2._X_.

Another possibility is a network filesystem where the name used to write to a remote directory is different from the name used to read it: for example, the Python interpreter accessed as /usr/local/bin/python might search for modules in /usr/local/lib/python2._X_, but those modules would have to be installed to, say, /mnt/_@server_/export/lib/python2._X_.

posix_prefix¶

nt¶

Installation path functions¶

sysconfig provides some functions to determine these installation paths.

sysconfig.get_scheme_names()¶

Return a tuple containing all schemes currently supported insysconfig.

sysconfig.get_default_scheme()¶

Return the default scheme name for the current platform.

Added in version 3.10: This function was previously named _get_default_scheme() and considered an implementation detail.

Changed in version 3.11: When Python runs from a virtual environment, the venv scheme is returned.

sysconfig.get_preferred_scheme(key)¶

Return a preferred scheme name for an installation layout specified by key.

key must be either "prefix", "home", or "user".

The return value is a scheme name listed in get_scheme_names(). It can be passed to sysconfig functions that take a scheme argument, such as get_paths().

Added in version 3.10.

Changed in version 3.11: When Python runs from a virtual environment and key="prefix", the venv scheme is returned.

sysconfig._get_preferred_schemes()¶

Return a dict containing preferred scheme names on the current platform. Python implementers and redistributors may add their preferred schemes to the _INSTALL_SCHEMES module-level global value, and modify this function to return those scheme names, to e.g. provide different schemes for system and language package managers to use, so packages installed by either do not mix with those by the other.

End users should not use this function, but get_default_scheme() andget_preferred_scheme() instead.

Added in version 3.10.

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 path name, from the install scheme named scheme.

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

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.

get_path() will use the variables returned by 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 byget_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 returned by get_config_vars().

If expand is set to False, the path will not be expanded using the variables.

If name is not found, raise a KeyError.

sysconfig.get_paths([_scheme_[, _vars_[, _expand_]]])¶

Return a dictionary containing all installation paths corresponding to an installation scheme. See 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, get_paths() will raise aKeyError.

Other functions¶

sysconfig.get_python_version()¶

Return the MAJOR.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 and platform-specific built distributions. Typically includes the OS name and version and the architecture (as supplied by os.uname()), although the exact information included depends on the OS; e.g., on Linux, the kernel version isn’t particularly important.

Examples of returned values:

• linux-i586
• linux-alpha (?)
• solaris-2.6-sun4u

Windows will return one of:

• win-amd64 (64-bit Windows on AMD64, aka x86_64, Intel64, and EM64T)
• win-arm64 (64-bit Windows on ARM64, aka AArch64)
• win32 (all others - specifically, sys.platform is returned)

macOS 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 sys.platform.

sysconfig.is_python_build()¶

Return True if the running Python interpreter was built from source and is being run from its built location, and not from a location resulting from e.g. running make install or installing via a binary installer.

sysconfig.parse_config_h(_fp_[, _vars_])¶

Parse a config.h-style file.

fp is a file-like object pointing to the 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.

sysconfig.get_config_h_filename()¶

Return the path of pyconfig.h.

sysconfig.get_makefile_filename()¶

Return the path of Makefile.

Command-line usage¶

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

$ python -m sysconfig Platform: "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().