1 """A pure Python implementation of import."""
2 __all__ = ['__import__', 'import_module', 'invalidate_caches', 'reload']
3
4 # Bootstrap help #####################################################
5
6 # Until bootstrapping is complete, DO NOT import any modules that attempt
7 # to import importlib._bootstrap (directly or indirectly). Since this
8 # partially initialised package would be present in sys.modules, those
9 # modules would get an uninitialised copy of the source version, instead
10 # of a fully initialised version (either the frozen one or the one
11 # initialised below if the frozen one is not available).
12 import _imp # Just the builtin component, NOT the full Python module
13 import sys
14
15 try:
16 import _frozen_importlib as _bootstrap
17 except ImportError:
18 from . import _bootstrap
19 _bootstrap._setup(sys, _imp)
20 else:
21 # importlib._bootstrap is the built-in import, ensure we don't create
22 # a second copy of the module.
23 _bootstrap.__name__ = 'importlib._bootstrap'
24 _bootstrap.__package__ = 'importlib'
25 try:
26 _bootstrap.__file__ = __file__.replace('__init__.py', '_bootstrap.py')
27 except NameError:
28 # __file__ is not guaranteed to be defined, e.g. if this code gets
29 # frozen by a tool like cx_Freeze.
30 pass
31 sys.modules['importlib._bootstrap'] = _bootstrap
32
33 try:
34 import _frozen_importlib_external as _bootstrap_external
35 except ImportError:
36 from . import _bootstrap_external
37 _bootstrap_external._set_bootstrap_module(_bootstrap)
38 _bootstrap._bootstrap_external = _bootstrap_external
39 else:
40 _bootstrap_external.__name__ = 'importlib._bootstrap_external'
41 _bootstrap_external.__package__ = 'importlib'
42 try:
43 _bootstrap_external.__file__ = __file__.replace('__init__.py', '_bootstrap_external.py')
44 except NameError:
45 # __file__ is not guaranteed to be defined, e.g. if this code gets
46 # frozen by a tool like cx_Freeze.
47 pass
48 sys.modules['importlib._bootstrap_external'] = _bootstrap_external
49
50 # To simplify imports in test code
51 _pack_uint32 = _bootstrap_external._pack_uint32
52 _unpack_uint32 = _bootstrap_external._unpack_uint32
53
54 # Fully bootstrapped at this point, import whatever you like, circular
55 # dependencies and startup overhead minimisation permitting :)
56
57 import warnings
58
59
60 # Public API #########################################################
61
62 from ._bootstrap import __import__
63
64
65 def invalidate_caches():
66 """Call the invalidate_caches() method on all meta path finders stored in
67 sys.meta_path (where implemented)."""
68 for finder in sys.meta_path:
69 if hasattr(finder, 'invalidate_caches'):
70 finder.invalidate_caches()
71
72
73 def find_loader(name, path=None):
74 """Return the loader for the specified module.
75
76 This is a backward-compatible wrapper around find_spec().
77
78 This function is deprecated in favor of importlib.util.find_spec().
79
80 """
81 warnings.warn('Deprecated since Python 3.4 and slated for removal in '
82 'Python 3.12; use importlib.util.find_spec() instead',
83 DeprecationWarning, stacklevel=2)
84 try:
85 loader = sys.modules[name].__loader__
86 if loader is None:
87 raise ValueError('{}.__loader__ is None'.format(name))
88 else:
89 return loader
90 except KeyError:
91 pass
92 except AttributeError:
93 raise ValueError('{}.__loader__ is not set'.format(name)) from None
94
95 spec = _bootstrap._find_spec(name, path)
96 # We won't worry about malformed specs (missing attributes).
97 if spec is None:
98 return None
99 if spec.loader is None:
100 if spec.submodule_search_locations is None:
101 raise ImportError('spec for {} missing loader'.format(name),
102 name=name)
103 raise ImportError('namespace packages do not have loaders',
104 name=name)
105 return spec.loader
106
107
108 def import_module(name, package=None):
109 """Import a module.
110
111 The 'package' argument is required when performing a relative import. It
112 specifies the package to use as the anchor point from which to resolve the
113 relative import to an absolute import.
114
115 """
116 level = 0
117 if name.startswith('.'):
118 if not package:
119 msg = ("the 'package' argument is required to perform a relative "
120 "import for {!r}")
121 raise TypeError(msg.format(name))
122 for character in name:
123 if character != '.':
124 break
125 level += 1
126 return _bootstrap._gcd_import(name[level:], package, level)
127
128
129 _RELOADING = {}
130
131
132 def reload(module):
133 """Reload the module and return it.
134
135 The module must have been successfully imported before.
136
137 """
138 try:
139 name = module.__spec__.name
140 except AttributeError:
141 try:
142 name = module.__name__
143 except AttributeError:
144 raise TypeError("reload() argument must be a module")
145
146 if sys.modules.get(name) is not module:
147 msg = "module {} not in sys.modules"
148 raise ImportError(msg.format(name), name=name)
149 if name in _RELOADING:
150 return _RELOADING[name]
151 _RELOADING[name] = module
152 try:
153 parent_name = name.rpartition('.')[0]
154 if parent_name:
155 try:
156 parent = sys.modules[parent_name]
157 except KeyError:
158 msg = "parent {!r} not in sys.modules"
159 raise ImportError(msg.format(parent_name),
160 name=parent_name) from None
161 else:
162 pkgpath = parent.__path__
163 else:
164 pkgpath = None
165 target = module
166 spec = module.__spec__ = _bootstrap._find_spec(name, pkgpath, target)
167 if spec is None:
168 raise ModuleNotFoundError(f"spec not found for the module {name!r}", name=name)
169 _bootstrap._exec(spec, module)
170 # The module may have replaced itself in sys.modules!
171 return sys.modules[name]
172 finally:
173 try:
174 del _RELOADING[name]
175 except KeyError:
176 pass