cpython/Lib/site.py

"""Append module search paths for third-party packages to sys.path.

****************************************************************
* This module is automatically imported during initialization. *
****************************************************************

This will append site-specific paths to the module search path.  On
Unix (including Mac OSX), it starts with sys.prefix and
sys.exec_prefix (if different) and appends
lib/python<version>/site-packages as well as lib/site-python.
On other platforms (such as Windows), it tries each of the
prefixes directly, as well as with lib/site-packages appended.  The
resulting directories, if they exist, are appended to sys.path, and
also inspected for path configuration files.

If a file named "pyvenv.cfg" exists one directory above sys.executable,
sys.prefix and sys.exec_prefix are set to that directory and
it is also checked for site-packages and site-python (sys.base_prefix and
sys.base_exec_prefix will always be the "real" prefixes of the Python
installation). If "pyvenv.cfg" (a bootstrap configuration file) contains
the key "include-system-site-packages" set to anything other than "false"
(case-insensitive), the system-level prefixes will still also be
searched for site-packages; otherwise they won't.

All of the resulting site-specific directories, if they exist, are
appended to sys.path, and also inspected for path configuration
files.

A path configuration file is a file whose name has the form
<package>.pth; its contents are additional directories (one per line)
to be added to sys.path.  Non-existing directories (or
non-directories) are never added to sys.path; no directory is added to
sys.path more than once.  Blank lines and lines beginning with
'#' are skipped. Lines starting with 'import' are executed.

For example, suppose sys.prefix and sys.exec_prefix are set to
/usr/local and there is a directory /usr/local/lib/python2.5/site-packages
with three subdirectories, foo, bar and spam, and two path
configuration files, foo.pth and bar.pth.  Assume foo.pth contains the
following:

  # foo package configuration
  foo
  bar
  bletch

and bar.pth contains:

  # bar package configuration
  bar

Then the following directories are added to sys.path, in this order:

  /usr/local/lib/python2.5/site-packages/bar
  /usr/local/lib/python2.5/site-packages/foo

Note that bletch is omitted because it doesn't exist; bar precedes foo
because bar.pth comes alphabetically before foo.pth; and spam is
omitted because it is not mentioned in either path configuration file.

After these path manipulations, an attempt is made to import a module
named sitecustomize, which can perform arbitrary additional
site-specific customizations.  If this import fails with an
ImportError exception, it is silently ignored.

"""

import sys
import os
import re
import builtins

# Prefixes for site-packages; add additional prefixes like /usr/local here
PREFIXES = [sys.prefix, sys.exec_prefix]
# Enable per user site-packages directory
# set it to False to disable the feature or True to force the feature
ENABLE_USER_SITE = None

# for distutils.commands.install
# These values are initialized by the getuserbase() and getusersitepackages()
# functions, through the main() function when Python starts.
USER_SITE = None
USER_BASE = None


def makepath(*paths):
    dir = os.path.join(*paths)
    try:
        dir = os.path.abspath(dir)
    except OSError:
        pass
    return dir, os.path.normcase(dir)


def abs_paths():
    """Set all module __file__ and __cached__ attributes to an absolute path"""
    for m in set(sys.modules.values()):
        if (getattr(getattr(m, '__loader__', None), '__module__', None) !=
                '_frozen_importlib'):
            continue   # don't mess with a PEP 302-supplied __file__
        try:
            m.__file__ = os.path.abspath(m.__file__)
        except (AttributeError, OSError):
            pass
        try:
            m.__cached__ = os.path.abspath(m.__cached__)
        except (AttributeError, OSError):
            pass


def removeduppaths():
    """ Remove duplicate entries from sys.path along with making them
    absolute"""
    # This ensures that the initial path provided by the interpreter contains
    # only absolute pathnames, even if we're running from the build directory.
    L = []
    known_paths = set()
    for dir in sys.path:
        # Filter out duplicate paths (on case-insensitive file systems also
        # if they only differ in case); turn relative paths into absolute
        # paths.
        dir, dircase = makepath(dir)
        if not dircase in known_paths:
            L.append(dir)
            known_paths.add(dircase)
    sys.path[:] = L
    return known_paths


def _init_pathinfo():
    """Return a set containing all existing directory entries from sys.path"""
    d = set()
    for dir in sys.path:
        try:
            if os.path.isdir(dir):
                dir, dircase = makepath(dir)
                d.add(dircase)
        except TypeError:
            continue
    return d


def addpackage(sitedir, name, known_paths):
    """Process a .pth file within the site-packages directory:
       For each line in the file, either combine it with sitedir to a path
       and add that to known_paths, or execute it if it starts with 'import '.
    """
    if known_paths is None:
        known_paths = _init_pathinfo()
        reset = 1
    else:
        reset = 0
    fullname = os.path.join(sitedir, name)
    try:
        f = open(fullname, "r")
    except OSError:
        return
    with f:
        for n, line in enumerate(f):
            if line.startswith("#"):
                continue
            try:
                if line.startswith(("import ", "import\t")):
                    exec(line)
                    continue
                line = line.rstrip()
                dir, dircase = makepath(sitedir, line)
                if not dircase in known_paths and os.path.exists(dir):
                    sys.path.append(dir)
                    known_paths.add(dircase)
            except Exception:
                print("Error processing line {:d} of {}:\n".format(n+1, fullname),
                      file=sys.stderr)
                import traceback
                for record in traceback.format_exception(*sys.exc_info()):
                    for line in record.splitlines():
                        print('  '+line, file=sys.stderr)
                print("\nRemainder of file ignored", file=sys.stderr)
                break
    if reset:
        known_paths = None
    return known_paths


def addsitedir(sitedir, known_paths=None):
    """Add 'sitedir' argument to sys.path if missing and handle .pth files in
    'sitedir'"""
    if known_paths is None:
        known_paths = _init_pathinfo()
        reset = 1
    else:
        reset = 0
    sitedir, sitedircase = makepath(sitedir)
    if not sitedircase in known_paths:
        sys.path.append(sitedir)        # Add path component
        known_paths.add(sitedircase)
    try:
        names = os.listdir(sitedir)
    except OSError:
        return
    names = [name for name in names if name.endswith(".pth")]
    for name in sorted(names):
        addpackage(sitedir, name, known_paths)
    if reset:
        known_paths = None
    return known_paths


def check_enableusersite():
    """Check if user site directory is safe for inclusion

    The function tests for the command line flag (including environment var),
    process uid/gid equal to effective uid/gid.

    None: Disabled for security reasons
    False: Disabled by user (command line option)
    True: Safe and enabled
    """
    if sys.flags.no_user_site:
        return False

    if hasattr(os, "getuid") and hasattr(os, "geteuid"):
        # check process uid == effective uid
        if os.geteuid() != os.getuid():
            return None
    if hasattr(os, "getgid") and hasattr(os, "getegid"):
        # check process gid == effective gid
        if os.getegid() != os.getgid():
            return None

    return True

def getuserbase():
    """Returns the `user base` directory path.

    The `user base` directory can be used to store data. If the global
    variable ``USER_BASE`` is not initialized yet, this function will also set
    it.
    """
    global USER_BASE
    if USER_BASE is not None:
        return USER_BASE
    from sysconfig import get_config_var
    USER_BASE = get_config_var('userbase')
    return USER_BASE

def getusersitepackages():
    """Returns the user-specific site-packages directory path.

    If the global variable ``USER_SITE`` is not initialized yet, this
    function will also set it.
    """
    global USER_SITE
    user_base = getuserbase() # this will also set USER_BASE

    if USER_SITE is not None:
        return USER_SITE

    from sysconfig import get_path

    if sys.platform == 'darwin':
        from sysconfig import get_config_var
        if get_config_var('PYTHONFRAMEWORK'):
            USER_SITE = get_path('purelib', 'osx_framework_user')
            return USER_SITE

    USER_SITE = get_path('purelib', '%s_user' % os.name)
    return USER_SITE

def addusersitepackages(known_paths):
    """Add a per user site-package to sys.path

    Each user has its own python directory with site-packages in the
    home directory.
    """
    # get the per user site-package path
    # this call will also make sure USER_BASE and USER_SITE are set
    user_site = getusersitepackages()

    if ENABLE_USER_SITE and os.path.isdir(user_site):
        addsitedir(user_site, known_paths)
    return known_paths

def getsitepackages(prefixes=None):
    """Returns a list containing all global site-packages directories
    (and possibly site-python).

    For each directory present in ``prefixes`` (or the global ``PREFIXES``),
    this function will find its `site-packages` subdirectory depending on the
    system environment, and will return a list of full paths.
    """
    sitepackages = []
    seen = set()

    if prefixes is None:
        prefixes = PREFIXES

    for prefix in prefixes:
        if not prefix or prefix in seen:
            continue
        seen.add(prefix)

        if os.sep == '/':
            sitepackages.append(os.path.join(prefix, "lib",
                                        "python" + sys.version[:3],
                                        "site-packages"))
            sitepackages.append(os.path.join(prefix, "lib", "site-python"))
        else:
            sitepackages.append(prefix)
            sitepackages.append(os.path.join(prefix, "lib", "site-packages"))
        if sys.platform == "darwin":
            # for framework builds *only* we add the standard Apple
            # locations.
            from sysconfig import get_config_var
            framework = get_config_var("PYTHONFRAMEWORK")
            if framework:
                sitepackages.append(
                        os.path.join("/Library", framework,
                            sys.version[:3], "site-packages"))
    return sitepackages

def addsitepackages(known_paths, prefixes=None):
    """Add site-packages (and possibly site-python) to sys.path"""
    for sitedir in getsitepackages(prefixes):
        if os.path.isdir(sitedir):
            addsitedir(sitedir, known_paths)

    return known_paths

def setquit():
    """Define new builtins 'quit' and 'exit'.

    These are objects which make the interpreter exit when called.
    The repr of each object contains a hint at how it works.

    """
    if os.sep == ':':
        eof = 'Cmd-Q'
    elif os.sep == '\\':
        eof = 'Ctrl-Z plus Return'
    else:
        eof = 'Ctrl-D (i.e. EOF)'

    class Quitter(object):
        def __init__(self, name):
            self.name = name
        def __repr__(self):
            return 'Use %s() or %s to exit' % (self.name, eof)
        def __call__(self, code=None):
            # Shells like IDLE catch the SystemExit, but listen when their
            # stdin wrapper is closed.
            try:
                sys.stdin.close()
            except:
                pass
            raise SystemExit(code)
    builtins.quit = Quitter('quit')
    builtins.exit = Quitter('exit')


class _Printer(object):
    """interactive prompt objects for printing the license text, a list of
    contributors and the copyright notice."""

    MAXLINES = 23

    def __init__(self, name, data, files=(), dirs=()):
        self.__name = name
        self.__data = data
        self.__files = files
        self.__dirs = dirs
        self.__lines = None

    def __setup(self):
        if self.__lines:
            return
        data = None
        for dir in self.__dirs:
            for filename in self.__files:
                filename = os.path.join(dir, filename)
                try:
                    with open(filename, "r") as fp:
                        data = fp.read()
                    break
                except OSError:
                    pass
            if data:
                break
        if not data:
            data = self.__data
        self.__lines = data.split('\n')
        self.__linecnt = len(self.__lines)

    def __repr__(self):
        self.__setup()
        if len(self.__lines) <= self.MAXLINES:
            return "\n".join(self.__lines)
        else:
            return "Type %s() to see the full %s text" % ((self.__name,)*2)

    def __call__(self):
        self.__setup()
        prompt = 'Hit Return for more, or q (and Return) to quit: '
        lineno = 0
        while 1:
            try:
                for i in range(lineno, lineno + self.MAXLINES):
                    print(self.__lines[i])
            except IndexError:
                break
            else:
                lineno += self.MAXLINES
                key = None
                while key is None:
                    key = input(prompt)
                    if key not in ('', 'q'):
                        key = None
                if key == 'q':
                    break

def setcopyright():
    """Set 'copyright' and 'credits' in builtins"""
    builtins.copyright = _Printer("copyright", sys.copyright)
    if sys.platform[:4] == 'java':
        builtins.credits = _Printer(
            "credits",
            "Jython is maintained by the Jython developers (www.jython.org).")
    else:
        builtins.credits = _Printer("credits", """\
    Thanks to CWI, CNRI, BeOpen.com, Zope Corporation and a cast of thousands
    for supporting Python development.  See www.python.org for more information.""")
    here = os.path.dirname(os.__file__)
    builtins.license = _Printer(
        "license", "See http://www.python.org/%.3s/license.html" % sys.version,
        ["LICENSE.txt", "LICENSE"],
        [os.path.join(here, os.pardir), here, os.curdir])


class _Helper(object):
    """Define the builtin 'help'.
    This is a wrapper around pydoc.help (with a twist).

    """

    def __repr__(self):
        return "Type help() for interactive help, " \
               "or help(object) for help about object."
    def __call__(self, *args, **kwds):
        import pydoc
        return pydoc.help(*args, **kwds)

def sethelper():
    builtins.help = _Helper()

def aliasmbcs():
    """On Windows, some default encodings are not provided by Python,
    while they are always available as "mbcs" in each locale. Make
    them usable by aliasing to "mbcs" in such a case."""
    if sys.platform == 'win32':
        import locale, codecs
        enc = locale.getdefaultlocale()[1]
        if enc.startswith('cp'):            # "cp***" ?
            try:
                codecs.lookup(enc)
            except LookupError:
                import encodings
                encodings._cache[enc] = encodings._unknown
                encodings.aliases.aliases[enc] = 'mbcs'


CONFIG_LINE = re.compile(r'^(?P<key>(\w|[-_])+)\s*=\s*(?P<value>.*)\s*$')

def venv(known_paths):
    global PREFIXES, ENABLE_USER_SITE

    env = os.environ
    if sys.platform == 'darwin' and '__PYVENV_LAUNCHER__' in env:
        executable = os.environ['__PYVENV_LAUNCHER__']
    else:
        executable = sys.executable
    exe_dir, _ = os.path.split(os.path.abspath(executable))
    site_prefix = os.path.dirname(exe_dir)
    sys._home = None
    conf_basename = 'pyvenv.cfg'
    candidate_confs = [
        conffile for conffile in (
            os.path.join(exe_dir, conf_basename),
            os.path.join(site_prefix, conf_basename)
            )
        if os.path.isfile(conffile)
        ]

    if candidate_confs:
        virtual_conf = candidate_confs[0]
        system_site = "true"
        with open(virtual_conf) as f:
            for line in f:
                line = line.strip()
                m = CONFIG_LINE.match(line)
                if m:
                    d = m.groupdict()
                    key, value = d['key'].lower(), d['value']
                    if key == 'include-system-site-packages':
                        system_site = value.lower()
                    elif key == 'home':
                        sys._home = value

        sys.prefix = sys.exec_prefix = site_prefix

        # Doing this here ensures venv takes precedence over user-site
        addsitepackages(known_paths, [sys.prefix])

        # addsitepackages will process site_prefix again if its in PREFIXES,
        # but that's ok; known_paths will prevent anything being added twice
        if system_site == "true":
            PREFIXES.insert(0, sys.prefix)
        else:
            PREFIXES = [sys.prefix]
            ENABLE_USER_SITE = False

    return known_paths


def execsitecustomize():
    """Run custom site specific code, if available."""
    try:
        import sitecustomize
    except ImportError:
        pass
    except Exception as err:
        if os.environ.get("PYTHONVERBOSE"):
            sys.excepthook(*sys.exc_info())
        else:
            sys.stderr.write(
                "Error in sitecustomize; set PYTHONVERBOSE for traceback:\n"
                "%s: %s\n" %
                (err.__class__.__name__, err))


def execusercustomize():
    """Run custom user specific code, if available."""
    try:
        import usercustomize
    except ImportError:
        pass
    except Exception as err:
        if os.environ.get("PYTHONVERBOSE"):
            sys.excepthook(*sys.exc_info())
        else:
            sys.stderr.write(
                "Error in usercustomize; set PYTHONVERBOSE for traceback:\n"
                "%s: %s\n" %
                (err.__class__.__name__, err))


def main():
    """Add standard site-specific directories to the module search path.

    This function is called automatically when this module is imported,
    unless the python interpreter was started with the -S flag.
    """
    global ENABLE_USER_SITE

    abs_paths()
    known_paths = removeduppaths()
    known_paths = venv(known_paths)
    if ENABLE_USER_SITE is None:
        ENABLE_USER_SITE = check_enableusersite()
    known_paths = addusersitepackages(known_paths)
    known_paths = addsitepackages(known_paths)
    setquit()
    setcopyright()
    sethelper()
    aliasmbcs()
    execsitecustomize()
    if ENABLE_USER_SITE:
        execusercustomize()

# Prevent edition of sys.path when python was started with -S and
# site is imported later.
if not sys.flags.no_site:
    main()

def _script():
    help = """\
    %s [--user-base] [--user-site]

    Without arguments print some useful information
    With arguments print the value of USER_BASE and/or USER_SITE separated
    by '%s'.

    Exit codes with --user-base or --user-site:
      0 - user site directory is enabled
      1 - user site directory is disabled by user
      2 - uses site directory is disabled by super user
          or for security reasons
     >2 - unknown error
    """
    args = sys.argv[1:]
    if not args:
        user_base = getuserbase()
        user_site = getusersitepackages()
        print("sys.path = [")
        for dir in sys.path:
            print("    %r," % (dir,))
        print("]")
        print("USER_BASE: %r (%s)" % (user_base,
            "exists" if os.path.isdir(user_base) else "doesn't exist"))
        print("USER_SITE: %r (%s)" % (user_site,
            "exists" if os.path.isdir(user_site) else "doesn't exist"))
        print("ENABLE_USER_SITE: %r" %  ENABLE_USER_SITE)
        sys.exit(0)

    buffer = []
    if '--user-base' in args:
        buffer.append(USER_BASE)
    if '--user-site' in args:
        buffer.append(USER_SITE)

    if buffer:
        print(os.pathsep.join(buffer))
        if ENABLE_USER_SITE:
            sys.exit(0)
        elif ENABLE_USER_SITE is False:
            sys.exit(1)
        elif ENABLE_USER_SITE is None:
            sys.exit(2)
        else:
            sys.exit(3)
    else:
        import textwrap
        print(textwrap.dedent(help % (sys.argv[0], os.pathsep)))
        sys.exit(10)

if __name__ == '__main__':
    _script()