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annotate Lib/importlib/__init__.py @ 79691:05c8928362ee

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Merge __next__ method link fixes with 3.3.
author Ezio Melotti <ezio.melotti@gmail.com>
date Fri, 12 Oct 2012 13:46:37 +0300
parents 0a75ce232f56
children 358be7742377
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
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1 """A pure Python implementation of import."""
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2 __all__ = ['__import__', 'import_module', 'invalidate_caches']
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3
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4 # Bootstrap help #####################################################
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5
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6 # Until bootstrapping is complete, DO NOT import any modules that attempt
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7 # to import importlib._bootstrap (directly or indirectly). Since this
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8 # partially initialised package would be present in sys.modules, those
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9 # modules would get an uninitialised copy of the source version, instead
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10 # of a fully initialised version (either the frozen one or the one
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11 # initialised below if the frozen one is not available).
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12 import _imp # Just the builtin component, NOT the full Python module
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13 import sys
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14
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15 try:
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16 import _frozen_importlib as _bootstrap
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17 except ImportError:
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18 from . import _bootstrap
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19 _bootstrap._setup(sys, _imp)
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20 else:
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21 # importlib._bootstrap is the built-in import, ensure we don't create
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22 # a second copy of the module.
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23 _bootstrap.__name__ = 'importlib._bootstrap'
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24 _bootstrap.__package__ = 'importlib'
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25 _bootstrap.__file__ = __file__.replace('__init__.py', '_bootstrap.py')
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26 sys.modules['importlib._bootstrap'] = _bootstrap
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27
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28 # To simplify imports in test code
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29 _w_long = _bootstrap._w_long
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30 _r_long = _bootstrap._r_long
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31
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32 # Fully bootstrapped at this point, import whatever you like, circular
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33 # dependencies and startup overhead minimisation permitting :)
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34
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35 # Public API #########################################################
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36
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37 from ._bootstrap import __import__
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38
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39
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40 def invalidate_caches():
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41 """Call the invalidate_caches() method on all meta path finders stored in
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42 sys.meta_path (where implemented)."""
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43 for finder in sys.meta_path:
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44 if hasattr(finder, 'invalidate_caches'):
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45 finder.invalidate_caches()
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47
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48 def find_loader(name, path=None):
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49 """Find the loader for the specified module.
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50
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51 First, sys.modules is checked to see if the module was already imported. If
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52 so, then sys.modules[name].__loader__ is returned. If that happens to be
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53 set to None, then ValueError is raised. If the module is not in
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54 sys.modules, then sys.meta_path is searched for a suitable loader with the
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55 value of 'path' given to the finders. None is returned if no loader could
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56 be found.
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57
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58 Dotted names do not have their parent packages implicitly imported.
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59
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60 """
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61 try:
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62 loader = sys.modules[name].__loader__
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63 if loader is None:
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64 raise ValueError('{}.__loader__ is None'.format(name))
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65 else:
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66 return loader
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67 except KeyError:
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68 pass
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69 return _bootstrap._find_module(name, path)
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70
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71
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72 def import_module(name, package=None):
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73 """Import a module.
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74
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75 The 'package' argument is required when performing a relative import. It
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76 specifies the package to use as the anchor point from which to resolve the
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77 relative import to an absolute import.
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78
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79 """
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80 level = 0
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81 if name.startswith('.'):
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82 if not package:
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83 raise TypeError("relative imports require the 'package' argument")
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84 for character in name:
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85 if character != '.':
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86 break
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87 level += 1
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88 return _bootstrap._gcd_import(name[level:], package, level)