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 usingsetuptools.

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.

用法範例：

>>>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++']

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.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 isthe default scheme used when Python or a component is installed.

• posix_home: scheme for POSIX platforms, when thehome option is used.This scheme defines paths located under a specific home prefix.

• posix_user: scheme for POSIX platforms, when theuser option is used.This scheme defines paths located under the user's home directory(site.USER_BASE).

• posix_venv: scheme forPythonvirtualenvironments on POSIXplatforms; by default it is the same asposix_prefix.

• nt: scheme for Windows.This is the default scheme used when Python or a component is installed.

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

• nt_venv: scheme forPythonvirtualenvironments on Windows;by default it is the same asnt.

• venv: a scheme with values from eitherposix_venv ornt_venv dependingon the platform Python runs on.

• osx_framework_user: scheme for macOS, 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 ('pure' Python).

• include: directory for non-platform-specific header files forthe Python C-API.

• platinclude: directory for platform-specific header files forthe 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'thave write permission to the global site-packages directory or don't want toinstall into it.

Files will be installed into subdirectories ofsite.USER_BASE (writtenasuserbase hereafter). This scheme installs pure Python modules andextension modules in the same location (also known assite.USER_SITE).

Home scheme¶

The idea behind the "home scheme" is that you build and maintain a personalstash 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 theirhome directory have a layout similar to/usr/ or/usr/local/.This scheme can be used by anyone, regardless of the operating system theyare installing for.

Prefix scheme¶

The "prefix scheme" is useful when you wish to use one Python installation toperform the build/install (i.e., to run the setup script), but install modulesinto the third-party module directory of a different Python installation (orsomething that looks like a different Python installation). If this sounds atrifle 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, ratherthan 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 wantthem 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 aremote directory is different from the name used to read it: for example, thePython interpreter accessed as/usr/local/bin/python might search formodules in/usr/local/lib/python2.X, but those modules would have tobe installed to, say,/mnt/@server/export/lib/python2.X.

安裝路徑函式¶

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.

在 3.10 版被加入:This function was previously named_get_default_scheme() andconsidered an implementation detail.

在 3.11 版的變更:When Python runs from a virtual environment,thevenv scheme is returned.

sysconfig.get_preferred_scheme(key)¶

Return a preferred scheme name for an installation layout specified bykey.

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

The return value is a scheme name listed inget_scheme_names(). Itcan be passed tosysconfig functions that take ascheme argument,such asget_paths().

在 3.10 版被加入.

在 3.11 版的變更:When Python runs from a virtual environment andkey="prefix",thevenv 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 tothe_INSTALL_SCHEMES module-level global value, and modify this functionto return those scheme names, to e.g. provide different schemes for systemand language package managers to use, so packages installed by either do notmix with those by the other.

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

在 3.10 版被加入.

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 returned byget_config_vars().

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

如果找不到name，則引發KeyError。

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.

其他函式¶

sysconfig.get_python_version()¶

回傳MAJOR.MINOR Python 版本號碼字串。類似於'%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., on Linux, the kernelversion 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 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()¶

回傳pyconfig.h 的路徑。

sysconfig.get_makefile_filename()¶

回傳Makefile 的路徑。

命令列用法¶

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().