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125 lines
4.2 KiB
Python
125 lines
4.2 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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import types
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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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_bootstrap.__file__ = __file__.replace('__init__.py', '_bootstrap.py')
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sys.modules['importlib._bootstrap'] = _bootstrap
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# To simplify imports in test code
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_w_long = _bootstrap._w_long
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_r_long = _bootstrap._r_long
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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 find_loader(name, path=None):
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"""Find the loader for the specified module.
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First, sys.modules is checked to see if the module was already imported. If
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so, then sys.modules[name].__loader__ is returned. If that happens to be
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set to None, then ValueError is raised. If the module is not in
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sys.modules, then sys.meta_path is searched for a suitable loader with the
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value of 'path' given to the finders. None is returned if no loader could
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be found.
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Dotted names do not have their parent packages implicitly imported. You will
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most likely need to explicitly import all parent packages in the proper
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order for a submodule to get the correct loader.
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"""
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try:
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loader = sys.modules[name].__loader__
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if loader is None:
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raise ValueError('{}.__loader__ is None'.format(name))
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else:
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return loader
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except KeyError:
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pass
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except AttributeError:
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raise ValueError('{}.__loader__ is not set'.format(name))
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return _bootstrap._find_module(name, path)
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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("relative imports require the 'package' argument")
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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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if not module or not isinstance(module, types.ModuleType):
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raise TypeError("reload() argument must be module")
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name = module.__name__
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if name not in sys.modules:
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msg = "module {} not in sys.modules"
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raise ImportError(msg.format(name), 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 and parent_name not in sys.modules:
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msg = "parent {!r} not in sys.modules"
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raise ImportError(msg.format(parent_name), name=parent_name)
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return module.__loader__.load_module(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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