cpython/Lib/importlib/__init__.py

137 lines
4.6 KiB
Python

"""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 :)
# 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 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:
raise TypeError("the 'package' argument is required to perform a "
f"relative import for {name!r}")
for character in name:
if character != '.':
break
level += 1
return _bootstrap._gcd_import(name[level:], package, level)
_RELOADING = {}
def reload(module):
"""Reload the module and return it.
The module must have been successfully imported before.
"""
try:
name = module.__spec__.name
except AttributeError:
try:
name = module.__name__
except AttributeError:
raise TypeError("reload() argument must be a module")
if sys.modules.get(name) is not module:
raise ImportError(f"module {name} not in sys.modules", 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:
raise ImportError(f"parent {parent_name!r} not in sys.modules",
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