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"""Provide access to Python's configuration information. The specific
configuration variables available depend heavily on the platform and
configuration. The values may be retrieved using
get_config_var(name), and the list of variables is available via
get_config_vars().keys(). Additional convenience functions are also
Written by: Fred L. Drake, Jr.
Email: <>
import _imp
import os
import re
import sys
from .errors import DistutilsPlatformError
from .util import get_platform, get_host_platform
# These are needed in a couple of spots, so just compute them once.
PREFIX = os.path.normpath(sys.prefix)
EXEC_PREFIX = os.path.normpath(sys.exec_prefix)
BASE_PREFIX = os.path.normpath(sys.base_prefix)
BASE_EXEC_PREFIX = os.path.normpath(sys.base_exec_prefix)
# Path to the base directory of the project. On Windows the binary may
# live in project/PCbuild/win32 or project/PCbuild/amd64.
# set for cross builds
if "_PYTHON_PROJECT_BASE" in os.environ:
project_base = os.path.abspath(os.environ["_PYTHON_PROJECT_BASE"])
if sys.executable:
project_base = os.path.dirname(os.path.abspath(sys.executable))
# sys.executable can be empty if argv[0] has been changed and Python is
# unable to retrieve the real program name
project_base = os.getcwd()
# python_build: (Boolean) if true, we're either building Python or
# building an extension with an un-installed Python, so we use
# different (hard-wired) directories.
def _is_python_source_dir(d):
for fn in ("Setup", "Setup.local"):
if os.path.isfile(os.path.join(d, "Modules", fn)):
return True
return False
_sys_home = getattr(sys, '_home', None)
if == 'nt':
def _fix_pcbuild(d):
if d and os.path.normcase(d).startswith(
os.path.normcase(os.path.join(PREFIX, "PCbuild"))):
return PREFIX
return d
project_base = _fix_pcbuild(project_base)
_sys_home = _fix_pcbuild(_sys_home)
def _python_build():
if _sys_home:
return _is_python_source_dir(_sys_home)
return _is_python_source_dir(project_base)
python_build = _python_build()
# Calculate the build qualifier flags if they are defined. Adding the flags
# to the include and lib directories only makes sense for an installation, not
# an in-source build.
build_flags = ''
if not python_build:
build_flags = sys.abiflags
except AttributeError:
# It's not a configure-based build, so the sys module doesn't have
# this attribute, which is fine.
def get_python_version():
"""Return a string containing the major and minor Python version,
leaving off the patchlevel. Sample return values could be '1.5'
or '2.2'.
return '%d.%d' % sys.version_info[:2]
def get_python_inc(plat_specific=0, prefix=None):
"""Return the directory containing installed Python header files.
If 'plat_specific' is false (the default), this is the path to the
non-platform-specific header files, i.e. Python.h and so on;
otherwise, this is the path to platform-specific header files
(namely pyconfig.h).
If 'prefix' is supplied, use it instead of sys.base_prefix or
sys.base_exec_prefix -- i.e., ignore 'plat_specific'.
if prefix is None:
prefix = plat_specific and BASE_EXEC_PREFIX or BASE_PREFIX
if == "posix":
if python_build:
# Assume the executable is in the build directory. The
# pyconfig.h file should be in the same directory. Since
# the build directory may not be the source directory, we
# must use "srcdir" from the makefile to find the "Include"
# directory.
if plat_specific:
return _sys_home or project_base
incdir = os.path.join(get_config_var('srcdir'), 'Include')
return os.path.normpath(incdir)
python_dir = 'python' + get_python_version() + build_flags
return os.path.join(prefix, "include", python_dir)
elif == "nt":
if python_build:
# Include both the include and PC dir to ensure we can find
# pyconfig.h
return (os.path.join(prefix, "include") + os.path.pathsep +
os.path.join(prefix, "PC"))
return os.path.join(prefix, "include")
raise DistutilsPlatformError(
"I don't know where Python installs its C header files "
"on platform '%s'" %
def get_python_lib(plat_specific=0, standard_lib=0, prefix=None):
"""Return the directory containing the Python library (standard or
site additions).
If 'plat_specific' is true, return the directory containing
platform-specific modules, i.e. any module from a non-pure-Python
module distribution; otherwise, return the platform-shared library
directory. If 'standard_lib' is true, return the directory
containing standard Python library modules; otherwise, return the
directory for site-specific modules.
If 'prefix' is supplied, use it instead of sys.base_prefix or
sys.base_exec_prefix -- i.e., ignore 'plat_specific'.
if prefix is None:
if standard_lib:
prefix = plat_specific and BASE_EXEC_PREFIX or BASE_PREFIX
prefix = plat_specific and EXEC_PREFIX or PREFIX
if == "posix":
libpython = os.path.join(prefix,
"lib", "python" + get_python_version())
if standard_lib:
return libpython
return os.path.join(libpython, "site-packages")
elif == "nt":
if standard_lib:
return os.path.join(prefix, "Lib")
return os.path.join(prefix, "Lib", "site-packages")
raise DistutilsPlatformError(
"I don't know where Python installs its library "
"on platform '%s'" %
def customize_compiler(compiler):
"""Do any platform-specific customization of a CCompiler instance.
Mainly needed on Unix, so we can plug in the information that
varies across Unices and is stored in Python's Makefile.
if compiler.compiler_type == "unix":
if sys.platform == "darwin":
# Perform first-time customization of compiler-related
# config vars on OS X now that we know we need a compiler.
# This is primarily to support Pythons from binary
# installers. The kind and paths to build tools on
# the user system may vary significantly from the system
# that Python itself was built on. Also the user OS
# version and build tools may not support the same set
# of CPU architectures for universal builds.
global _config_vars
# Use get_config_var() to ensure _config_vars is initialized.
if not get_config_var('CUSTOMIZED_OSX_COMPILER'):
import _osx_support
_config_vars['CUSTOMIZED_OSX_COMPILER'] = 'True'
(cc, cxx, cflags, ccshared, ldshared, shlib_suffix, ar, ar_flags) = \
get_config_vars('CC', 'CXX', 'CFLAGS',
if 'CC' in os.environ:
newcc = os.environ['CC']
if (sys.platform == 'darwin'
and 'LDSHARED' not in os.environ
and ldshared.startswith(cc)):
# On OS X, if CC is overridden, use that as the default
# command for LDSHARED as well
ldshared = newcc + ldshared[len(cc):]
cc = newcc
if 'CXX' in os.environ:
cxx = os.environ['CXX']
if 'LDSHARED' in os.environ:
ldshared = os.environ['LDSHARED']
if 'CPP' in os.environ:
cpp = os.environ['CPP']
cpp = cc + " -E" # not always
if 'LDFLAGS' in os.environ:
ldshared = ldshared + ' ' + os.environ['LDFLAGS']
if 'CFLAGS' in os.environ:
cflags = cflags + ' ' + os.environ['CFLAGS']
ldshared = ldshared + ' ' + os.environ['CFLAGS']
if 'CPPFLAGS' in os.environ:
cpp = cpp + ' ' + os.environ['CPPFLAGS']
cflags = cflags + ' ' + os.environ['CPPFLAGS']
ldshared = ldshared + ' ' + os.environ['CPPFLAGS']
if 'AR' in os.environ:
ar = os.environ['AR']
if 'ARFLAGS' in os.environ:
archiver = ar + ' ' + os.environ['ARFLAGS']
archiver = ar + ' ' + ar_flags
cc_cmd = cc + ' ' + cflags
compiler_so=cc_cmd + ' ' + ccshared,
compiler.shared_lib_extension = shlib_suffix
def get_config_h_filename():
"""Return full pathname of installed pyconfig.h file."""
if python_build:
if == "nt":
inc_dir = os.path.join(_sys_home or project_base, "PC")
inc_dir = _sys_home or project_base
inc_dir = get_python_inc(plat_specific=1)
return os.path.join(inc_dir, 'pyconfig.h')
def get_makefile_filename():
"""Return full pathname of installed Makefile from the Python build."""
if python_build:
return os.path.join(_sys_home or project_base, "Makefile")
lib_dir = get_python_lib(plat_specific=0, standard_lib=1)
config_file = 'config-{}{}'.format(get_python_version(), build_flags)
if hasattr(sys.implementation, '_multiarch'):
config_file += '-%s' % sys.implementation._multiarch
return os.path.join(lib_dir, config_file, 'Makefile')
def parse_config_h(fp, g=None):
"""Parse a config.h-style 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.
if g is None:
g = {}
define_rx = re.compile("#define ([A-Z][A-Za-z0-9_]+) (.*)\n")
undef_rx = re.compile("/[*] #undef ([A-Z][A-Za-z0-9_]+) [*]/\n")
while True:
line = fp.readline()
if not line:
m = define_rx.match(line)
if m:
n, v =, 2)
try: v = int(v)
except ValueError: pass
g[n] = v
m = undef_rx.match(line)
if m:
g[] = 0
return g
# Regexes needed for parsing Makefile (and similar syntaxes,
# like old-style Setup files).
_variable_rx = re.compile(r"([a-zA-Z][a-zA-Z0-9_]+)\s*=\s*(.*)")
_findvar1_rx = re.compile(r"\$\(([A-Za-z][A-Za-z0-9_]*)\)")
_findvar2_rx = re.compile(r"\${([A-Za-z][A-Za-z0-9_]*)}")
def parse_makefile(fn, g=None):
"""Parse a Makefile-style 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.
from distutils.text_file import TextFile
fp = TextFile(fn, strip_comments=1, skip_blanks=1, join_lines=1, errors="surrogateescape")
if g is None:
g = {}
done = {}
notdone = {}
while True:
line = fp.readline()
if line is None: # eof
m = _variable_rx.match(line)
if m:
n, v =, 2)
v = v.strip()
# `$$' is a literal `$' in make
tmpv = v.replace('$$', '')
if "$" in tmpv:
notdone[n] = v
v = int(v)
except ValueError:
# insert literal `$'
done[n] = v.replace('$$', '$')
done[n] = v
# Variables with a 'PY_' prefix in the makefile. These need to
# be made available without that prefix through sysconfig.
# Special care is needed to ensure that variable expansion works, even
# if the expansion uses the name without a prefix.
renamed_variables = ('CFLAGS', 'LDFLAGS', 'CPPFLAGS')
# do variable interpolation here
while notdone:
for name in list(notdone):
value = notdone[name]
m = or
if m:
n =
found = True
if n in done:
item = str(done[n])
elif n in notdone:
# get it on a subsequent round
found = False
elif n in os.environ:
# do it like make: fall back to environment
item = os.environ[n]
elif n in renamed_variables:
if name.startswith('PY_') and name[3:] in renamed_variables:
item = ""
elif 'PY_' + n in notdone:
found = False
item = str(done['PY_' + n])
done[n] = item = ""
if found:
after = value[m.end():]
value = value[:m.start()] + item + after
if "$" in after:
notdone[name] = value
try: value = int(value)
except ValueError:
done[name] = value.strip()
done[name] = value
del notdone[name]
if name.startswith('PY_') \
and name[3:] in renamed_variables:
name = name[3:]
if name not in done:
done[name] = value
# bogus variable reference; just drop it since we can't deal
del notdone[name]
# strip spurious spaces
for k, v in done.items():
if isinstance(v, str):
done[k] = v.strip()
# save the results in the global dictionary
return g
def expand_makefile_vars(s, vars):
"""Expand Makefile-style variables -- "${foo}" or "$(foo)" -- in
'string' according to 'vars' (a dictionary mapping variable names to
values). Variables not present in 'vars' are silently expanded to the
empty string. The variable values in 'vars' should not contain further
variable expansions; if 'vars' is the output of 'parse_makefile()',
you're fine. Returns a variable-expanded version of 's'.
# This algorithm does multiple expansion, so if vars['foo'] contains
# "${bar}", it will expand ${foo} to ${bar}, and then expand
# ${bar}... and so forth. This is fine as long as 'vars' comes from
# 'parse_makefile()', which takes care of such expansions eagerly,
# according to make's variable expansion semantics.
while True:
m = or
if m:
(beg, end) = m.span()
s = s[0:beg] + vars.get( + s[end:]
return s
_config_vars = None
def _init_posix():
"""Initialize the module as appropriate for POSIX systems."""
# _sysconfigdata is generated at build time, see the sysconfig module
name = os.environ.get('_PYTHON_SYSCONFIGDATA_NAME',
multiarch=getattr(sys.implementation, '_multiarch', ''),
_temp = __import__(name, globals(), locals(), ['build_time_vars'], 0)
build_time_vars = _temp.build_time_vars
global _config_vars
_config_vars = {}
def _init_nt():
"""Initialize the module as appropriate for NT"""
g = {}
# set basic install directories
g['LIBDEST'] = get_python_lib(plat_specific=0, standard_lib=1)
g['BINLIBDEST'] = get_python_lib(plat_specific=1, standard_lib=1)
# XXX hmmm.. a normal install puts include files here
g['INCLUDEPY'] = get_python_inc(plat_specific=0)
g['EXT_SUFFIX'] = _imp.extension_suffixes()[0]
g['EXE'] = ".exe"
g['VERSION'] = get_python_version().replace(".", "")
g['BINDIR'] = os.path.dirname(os.path.abspath(sys.executable))
global _config_vars
_config_vars = g
def get_config_vars(*args):
"""With no arguments, return a dictionary of all configuration
variables relevant for the current platform. Generally this includes
everything needed to build extensions and install both pure modules and
extensions. On Unix, this means every variable defined in Python's
installed Makefile; on Windows it's a much smaller set.
With arguments, return a list of values that result from looking up
each argument in the configuration variable dictionary.
global _config_vars
if _config_vars is None:
func = globals().get("_init_" +
if func:
_config_vars = {}
# Normalized versions of prefix and exec_prefix are handy to have;
# in fact, these are the standard versions used most places in the
# Distutils.
_config_vars['prefix'] = PREFIX
_config_vars['exec_prefix'] = EXEC_PREFIX
# For backward compatibility, see issue19555
SO = _config_vars.get('EXT_SUFFIX')
if SO is not None:
_config_vars['SO'] = SO
# Always convert srcdir to an absolute path
srcdir = _config_vars.get('srcdir', project_base)
if == 'posix':
if python_build:
# If srcdir is a relative path (typically '.' or '..')
# then it should be interpreted relative to the directory
# containing Makefile.
base = os.path.dirname(get_makefile_filename())
srcdir = os.path.join(base, srcdir)
# srcdir is not meaningful since the installation is
# spread about the filesystem. We choose the
# directory containing the Makefile since we know it
# exists.
srcdir = os.path.dirname(get_makefile_filename())
_config_vars['srcdir'] = os.path.abspath(os.path.normpath(srcdir))
# Convert srcdir into an absolute path if it appears necessary.
# Normally it is relative to the build directory. However, during
# testing, for example, we might be running a non-installed python
# from a different directory.
if python_build and == "posix":
base = project_base
if (not os.path.isabs(_config_vars['srcdir']) and
base != os.getcwd()):
# srcdir is relative and we are not in the same directory
# as the executable. Assume executable is in the build
# directory and make srcdir absolute.
srcdir = os.path.join(base, _config_vars['srcdir'])
_config_vars['srcdir'] = os.path.normpath(srcdir)
# OS X platforms require special customization to handle
# multi-architecture, multi-os-version installers
if sys.platform == 'darwin':
import _osx_support
if args:
vals = []
for name in args:
return vals
return _config_vars
def get_config_var(name):
"""Return the value of a single variable using the dictionary
returned by 'get_config_vars()'. Equivalent to
if name == 'SO':
import warnings
warnings.warn('SO is deprecated, use EXT_SUFFIX', DeprecationWarning, 2)
return get_config_vars().get(name)
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