Lib/importlib/__init__.py

   1 """Backport of importlib.import_module from 3.x."""
   2 # While not critical (and in no way guaranteed!), it would be nice to keep this
   3 # code compatible with Python 2.3.
   4 import sys
   5
   6 def _resolve_name(name, package, level):
   7     """Return the absolute name of the module to be imported."""
   8     level -= 1
   9     try:
  10         if package.count('.') < level:
  11             raise ValueError("attempted relative import beyond top-level "
  12                               "package")
  13     except AttributeError:
  14         raise ValueError("'package' not set to a string")
  15     try:
  16         # rpartition is more "correct" and rfind is just as easy to use, but
  17         # neither are in Python 2.3.
  18         dot_rindex = package.rindex('.', level)[0]
  19         base = package[:dot_rindex]
  20     except ValueError:
  21         base = package
  22     if name:
  23         return "%s.%s" % (base, name)
  24     else:
  25         return base
  26
  27
  28 def import_module(name, package=None):
  29     """Import a module.
  30
  31     The 'package' argument is required when performing a relative import. It
  32     specifies the package to use as the anchor point from which to resolve the
  33     relative import to an absolute import.
  34
  35     """
  36     if name.startswith('.'):
  37         if not package:
  38             raise TypeError("relative imports require the 'package' argument")
  39         level = 0
  40         for character in name:
  41             if character != '.':
  42                 break
  43             level += 1
  44         name = _resolve_name(name[level:], package, level)
  45     # Try to import specifying the level to be as accurate as possible, but
  46     # realize that keyword arguments are not found in Python 2.3.
  47     try:
  48         __import__(name, level=0)
  49     except TypeError:
  50         __import__(name)
  51     return sys.modules[name]