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 import_module(name, package=None):
      74      """Import a module.
      75  
      76      The 'package' argument is required when performing a relative import. It
      77      specifies the package to use as the anchor point from which to resolve the
      78      relative import to an absolute import.
      79  
      80      """
      81      level = 0
      82      if name.startswith('.'):
      83          if not package:
      84              raise TypeError("the 'package' argument is required to perform a "
      85                              f"relative import for {name!r}")
      86          for character in name:
      87              if character != '.':
      88                  break
      89              level += 1
      90      return _bootstrap._gcd_import(name[level:], package, level)
      91  
      92  
      93  _RELOADING = {}
      94  
      95  
      96  def reload(module):
      97      """Reload the module and return it.
      98  
      99      The module must have been successfully imported before.
     100  
     101      """
     102      try:
     103          name = module.__spec__.name
     104      except AttributeError:
     105          try:
     106              name = module.__name__
     107          except AttributeError:
     108              raise TypeError("reload() argument must be a module")
     109  
     110      if sys.modules.get(name) is not module:
     111          raise ImportError(f"module {name} not in sys.modules", name=name)
     112      if name in _RELOADING:
     113          return _RELOADING[name]
     114      _RELOADING[name] = module
     115      try:
     116          parent_name = name.rpartition('.')[0]
     117          if parent_name:
     118              try:
     119                  parent = sys.modules[parent_name]
     120              except KeyError:
     121                  raise ImportError(f"parent {parent_name!r} not in sys.modules",
     122                                    name=parent_name) from None
     123              else:
     124                  pkgpath = parent.__path__
     125          else:
     126              pkgpath = None
     127          target = module
     128          spec = module.__spec__ = _bootstrap._find_spec(name, pkgpath, target)
     129          if spec is None:
     130              raise ModuleNotFoundError(f"spec not found for the module {name!r}", name=name)
     131          _bootstrap._exec(spec, module)
     132          # The module may have replaced itself in sys.modules!
     133          return sys.modules[name]
     134      finally:
     135          try:
     136              del _RELOADING[name]
     137          except KeyError:
     138              pass