mirror of https://github.com/python/cpython
137 lines
4.7 KiB
Python
137 lines
4.7 KiB
Python
"""A pure Python implementation of import."""
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__all__ = ['__import__', 'import_module', 'invalidate_caches', 'reload']
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# Bootstrap help #####################################################
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# Until bootstrapping is complete, DO NOT import any modules that attempt
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# to import importlib._bootstrap (directly or indirectly). Since this
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# partially initialised package would be present in sys.modules, those
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# modules would get an uninitialised copy of the source version, instead
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# of a fully initialised version (either the frozen one or the one
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# initialised below if the frozen one is not available).
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import _imp # Just the builtin component, NOT the full Python module
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import sys
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try:
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import _frozen_importlib as _bootstrap
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except ImportError:
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from . import _bootstrap
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_bootstrap._setup(sys, _imp)
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else:
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# importlib._bootstrap is the built-in import, ensure we don't create
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# a second copy of the module.
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_bootstrap.__name__ = 'importlib._bootstrap'
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_bootstrap.__package__ = 'importlib'
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try:
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_bootstrap.__file__ = __file__.replace('__init__.py', '_bootstrap.py')
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except NameError:
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# __file__ is not guaranteed to be defined, e.g. if this code gets
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# frozen by a tool like cx_Freeze.
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pass
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sys.modules['importlib._bootstrap'] = _bootstrap
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try:
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import _frozen_importlib_external as _bootstrap_external
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except ImportError:
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from . import _bootstrap_external
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_bootstrap_external._set_bootstrap_module(_bootstrap)
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_bootstrap._bootstrap_external = _bootstrap_external
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else:
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_bootstrap_external.__name__ = 'importlib._bootstrap_external'
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_bootstrap_external.__package__ = 'importlib'
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try:
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_bootstrap_external.__file__ = __file__.replace('__init__.py', '_bootstrap_external.py')
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except NameError:
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# __file__ is not guaranteed to be defined, e.g. if this code gets
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# frozen by a tool like cx_Freeze.
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pass
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sys.modules['importlib._bootstrap_external'] = _bootstrap_external
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# To simplify imports in test code
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_pack_uint32 = _bootstrap_external._pack_uint32
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_unpack_uint32 = _bootstrap_external._unpack_uint32
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# Fully bootstrapped at this point, import whatever you like, circular
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# dependencies and startup overhead minimisation permitting :)
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# Public API #########################################################
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from ._bootstrap import __import__
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def invalidate_caches():
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"""Call the invalidate_caches() method on all meta path finders stored in
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sys.meta_path (where implemented)."""
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for finder in sys.meta_path:
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if hasattr(finder, 'invalidate_caches'):
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finder.invalidate_caches()
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def import_module(name, package=None):
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"""Import a module.
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The 'package' argument is required when performing a relative import. It
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specifies the package to use as the anchor point from which to resolve the
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relative import to an absolute import.
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"""
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level = 0
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if name.startswith('.'):
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if not package:
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raise TypeError("the 'package' argument is required to perform a "
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f"relative import for {name!r}")
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for character in name:
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if character != '.':
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break
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level += 1
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return _bootstrap._gcd_import(name[level:], package, level)
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_RELOADING = {}
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def reload(module):
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"""Reload the module and return it.
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The module must have been successfully imported before.
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"""
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try:
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name = module.__spec__.name
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except AttributeError:
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try:
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name = module.__name__
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except AttributeError:
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raise TypeError("reload() argument must be a module") from None
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if sys.modules.get(name) is not module:
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raise ImportError(f"module {name} not in sys.modules", name=name)
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if name in _RELOADING:
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return _RELOADING[name]
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_RELOADING[name] = module
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try:
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parent_name = name.rpartition('.')[0]
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if parent_name:
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try:
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parent = sys.modules[parent_name]
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except KeyError:
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raise ImportError(f"parent {parent_name!r} not in sys.modules",
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name=parent_name) from None
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else:
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pkgpath = parent.__path__
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else:
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pkgpath = None
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target = module
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spec = module.__spec__ = _bootstrap._find_spec(name, pkgpath, target)
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if spec is None:
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raise ModuleNotFoundError(f"spec not found for the module {name!r}", name=name)
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_bootstrap._exec(spec, module)
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# The module may have replaced itself in sys.modules!
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return sys.modules[name]
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finally:
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try:
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del _RELOADING[name]
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except KeyError:
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pass
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