Need for speed: Patch #921466 : sys.path_importer_cache is now used to cache valid and

  invalid file paths for the built-in import machinery which leads to
  fewer open calls on startup.

  Also fix issue with PEP 302 style import hooks which lead to more open()
  calls than necessary.

1 files changed, 4 insertions, 2 deletions

diff --git a/Lib/pkgutil.py b/Lib/pkgutil.py
index ddf2a72761..26c797f0f6 100644
--- a/Lib/pkgutil.py
+++ b/Lib/pkgutil.py
@@ -340,11 +340,13 @@ def get_importer(path_item):
             importer = None
         sys.path_importer_cache.setdefault(path_item, importer)
 
-    if importer is None:
+    # The boolean values are used for caching valid and invalid
+    # file paths for the built-in import machinery
+    if importer in (None, True, False):
         try:
             importer = ImpImporter(path_item)
         except ImportError:
-            pass
+            importer = None
     return importer