Source code for importlib

"""A pure Python implementation of import."""
__all__ = ['__import__', 'import_module', 'invalidate_caches', 'reload']

# Bootstrap help #####################################################

# Until bootstrapping is complete, DO NOT import any modules that attempt
# to import importlib._bootstrap (directly or indirectly). Since this
# partially initialised package would be present in sys.modules, those
# modules would get an uninitialised copy of the source version, instead
# of a fully initialised version (either the frozen one or the one
# initialised below if the frozen one is not available).
import _imp  # Just the builtin component, NOT the full Python module
import sys

try:
    import _frozen_importlib as _bootstrap
except ImportError:
    from . import _bootstrap
    _bootstrap._setup(sys, _imp)
else:
    # importlib._bootstrap is the built-in import, ensure we don't create
    # a second copy of the module.
    _bootstrap.__name__ = 'importlib._bootstrap'
    _bootstrap.__package__ = 'importlib'
    try:
        _bootstrap.__file__ = __file__.replace('__init__.py', '_bootstrap.py')
    except NameError:
        # __file__ is not guaranteed to be defined, e.g. if this code gets
        # frozen by a tool like cx_Freeze.
        pass
    sys.modules['importlib._bootstrap'] = _bootstrap

try:
    import _frozen_importlib_external as _bootstrap_external
except ImportError:
    from . import _bootstrap_external
    _bootstrap_external._set_bootstrap_module(_bootstrap)
    _bootstrap._bootstrap_external = _bootstrap_external
else:
    _bootstrap_external.__name__ = 'importlib._bootstrap_external'
    _bootstrap_external.__package__ = 'importlib'
    try:
        _bootstrap_external.__file__ = __file__.replace('__init__.py', '_bootstrap_external.py')
    except NameError:
        # __file__ is not guaranteed to be defined, e.g. if this code gets
        # frozen by a tool like cx_Freeze.
        pass
    sys.modules['importlib._bootstrap_external'] = _bootstrap_external

# To simplify imports in test code
_pack_uint32 = _bootstrap_external._pack_uint32
_unpack_uint32 = _bootstrap_external._unpack_uint32

# Fully bootstrapped at this point, import whatever you like, circular
# dependencies and startup overhead minimisation permitting :)

import warnings


# Public API #########################################################

from ._bootstrap import __import__


def invalidate_caches():
    """Call the invalidate_caches() method on all meta path finders stored in
    sys.meta_path (where implemented)."""
    for finder in sys.meta_path:
        if hasattr(finder, 'invalidate_caches'):
            finder.invalidate_caches()


def find_loader(name, path=None):
    """Return the loader for the specified module.

    This is a backward-compatible wrapper around find_spec().

    This function is deprecated in favor of importlib.util.find_spec().

    """
    warnings.warn('Deprecated since Python 3.4 and slated for removal in '
                  'Python 3.12; use importlib.util.find_spec() instead',
                  DeprecationWarning, stacklevel=