Question

>>> import distutils.sysconfig
>>> distutils.sysconfig.get_python_lib()
/usr/lib/python2.7/dist-packages

But I want this path: /usr/local/lib/python2.7/dist-packages.
I can’t use the sysconfig module because it is only supported on python2.7 and there is no PyPI download to that module. so I could not even use a requirements file to let other users download it with pip.

So, is there any way to get the path to my installed packages that works for Linux and OS X operating systems? (or even all Unix based os’s)

Answer 1

If you need the specific functionality of the get_python_lib function, the source for that module is fairly straightforward and doesn’t use any Python 2.7 specific syntax at all; you could simply backport it.

You’d basically need the following definitions and two functions:

import os
import sys
from distutils.errors import DistutilsPlatformError


PREFIX = os.path.normpath(sys.prefix)
EXEC_PREFIX = os.path.normpath(sys.exec_prefix)


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 sys.version[:3]

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.prefix or
    sys.exec_prefix -- i.e., ignore 'plat_specific'.
    """
    if prefix is None:
        prefix = plat_specific and EXEC_PREFIX or PREFIX

    if os.name == "posix":
        libpython = os.path.join(prefix,
                                 "lib", "python" + get_python_version())
        if standard_lib:
            return libpython
        else:
            return os.path.join(libpython, "site-packages")

    elif os.name == "nt":
        if standard_lib:
            return os.path.join(prefix, "Lib")
        else:
            if get_python_version() < "2.2":
                return prefix
            else:
                return os.path.join(prefix, "Lib", "site-packages")

    elif os.name == "os2":
        if standard_lib:
            return os.path.join(prefix, "Lib")
        else:
            return os.path.join(prefix, "Lib", "site-packages")

    else:
        raise DistutilsPlatformError(
            "I don't know where Python installs its library "
            "on platform '%s'" % os.name)

You can cut the long function down to just the branch you need for your platform, of course; for OS X that’d be:

def get_python_lib(plat_specific=0, standard_lib=0, prefix=None):
    if prefix is None:
        prefix = plat_specific and EXEC_PREFIX or PREFIX

    libpython = os.path.join(prefix,
                             "lib", "python" + get_python_version())
    if standard_lib:
        return libpython
    else:
        return os.path.join(libpython, "site-packages")

Note that Debian patches this function to return dist-packages in the default case, this doesn’t apply to OS X.