bpo-40327: Improve atomicity, speed, and memory efficiency of the items() loop (GH...

diff --git a/Lib/pickle.py b/Lib/pickle.py
index d7adc162c98de959446a9263da462a286f505c27..1fc8b0d26c6c47b369f88e5e8633defd17ed9b1f 100644 (file)
--- a/Lib/pickle.py
+++ b/Lib/pickle.py
@@ -339,7 +339,7 @@ def whichmodule(obj, name):
         return module_name
     # Protect the iteration by using a list copy of sys.modules against dynamic
     # modules that trigger imports of other modules upon calls to getattr.
-    for module_name, module in list(sys.modules.items()):
+    for module_name, module in sys.modules.copy().items():
         if module_name == '__main__' or module is None:
             continue
         try: