"""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._setup(_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 types
import warnings
# Public API #########################################################
from ._bootstrap import __import__
[docs]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. '
'Use importlib.util.find_spec() instead.',
DeprecationWarning, stacklevel=2)
try:
loader = sys.modules[name].__loader__
if loader is None:
raise ValueError('{}.__loader__ is None'.format(name))
else:
return loader
except KeyError:
pass
except AttributeError:
raise ValueError('{}.__loader__ is not set'.format(name)) from None
spec = _bootstrap._find_spec(name, path)
# We won't worry about malformed specs (missing attributes).
if spec is None:
return None
if spec.loader is None:
if spec.submodule_search_locations is None:
raise ImportError('spec for {} missing loader'.format(name),
name=name)
raise ImportError('namespace packages do not have loaders',
name=name)
return spec.loader
[docs]def import_module(name, package=None):
"""Import a module.
The 'package' argument is required when performing a relative import. It
specifies the package to use as the anchor point from which to resolve the
relative import to an absolute import.
"""
level = 0
if name.startswith('.'):
if not package:
msg = ("the 'package' argument is required to perform a relative "
"import for {!r}")
raise TypeError(msg.format(name))
for character in name:
if character != '.':
break
level += 1
return _bootstrap._gcd_import(name[level:], package, level)
_RELOADING = {}
[docs]def reload(module):
"""Reload the module and return it.
The module must have been successfully imported before.
"""
if not module or not isinstance(module, types.ModuleType):
raise TypeError("reload() argument must be a module")
try:
name = module.__spec__.name
except AttributeError:
name = module.__name__
if sys.modules.get(name) is not module:
msg = "module {} not in sys.modules"
raise ImportError(msg.format(name), name=name)
if name in _RELOADING:
return _RELOADING[name]
_RELOADING[name] = module
try:
parent_name = name.rpartition('.')[0]
if parent_name:
try:
parent = sys.modules[parent_name]
except KeyError:
msg = "parent {!r} not in sys.modules"
raise ImportError(msg.format(parent_name),
name=parent_name) from None
else:
pkgpath = parent.__path__
else:
pkgpath = None
target = module
spec = module.__spec__ = _bootstrap._find_spec(name, pkgpath, target)
if spec is None:
raise ModuleNotFoundError(f"spec not found for the module {name!r}", name=name)
_bootstrap._exec(spec, module)
# The module may have replaced itself in sys.modules!
return sys.modules[name]
finally:
try:
del _RELOADING[name]
except KeyError:
pass