Meta path finders and path entry finders are different, but share an ABC

Lib/importlib/__init__.py

 """A pure Python implementation of import."""
 __all__ = ['__import__', 'import_module', 'invalidate_caches']
 
 # Bootstrap help #####################################################
 
 # Until bootstrapping is complete, DO NOT import any modules that attempt
 # to import importlib._bootstrap (directly or indirectly). Since this
 # partially initialised package would be present in sys.modules, those
 # modules would get an uninitialised copy of the source version, instead
 # of a fully initialised version (either the frozen one or the one
@@ skipping 20 matching lines @@
 
 # Fully bootstrapped at this point, import whatever you like, circular
 # dependencies and startup overhead minimisation permitting :)
 
 # Public API #########################################################
 
 from ._bootstrap import __import__
 
 
 def invalidate_caches():
-    """Call the invalidate_caches() method on all finders stored in
-    sys.path_importer_caches (where implemented)."""
-    for finder in sys.path_importer_cache.values():
+    """Call the invalidate_caches() method on all meta path finders stored in
+    sys.meta_path (where implemented)."""
+    for finder in sys.meta_path:
         if hasattr(finder, 'invalidate_caches'):
             finder.invalidate_caches()
 
 
 def find_loader(name, path=None):
     """Find the loader for the specified module.
 
     First, sys.modules is checked to see if the module was already imported. If
     so, then sys.modules[name].__loader__ is returned. If that happens to be
     set to None, then ValueError is raised. If the module is not in
@@ skipping 25 matching lines @@
     """
     level = 0
     if name.startswith('.'):
         if not package:
             raise TypeError("relative imports require the 'package' argument")
         for character in name:
             if character != '.':
                 break
             level += 1
     return _bootstrap._gcd_import(name[level:], package, level)