Issue #20884: Don't assume in importlib.__init__ that __file__ is

defined.

Lib/importlib/__init__.py

@@ -22,7 +22,12 @@ else:
     # a second copy of the module.
     _bootstrap.__name__ = 'importlib._bootstrap'
     _bootstrap.__package__ = 'importlib'
+    try:
         _bootstrap.__file__ = __file__.replace('__init__.py', '_bootstrap.py')
+    except NameError:
+        # __file__ is not guaranteed to be defined, e.g. if this code gets
+        # frozen by a tool like cx_Freeze.
+        pass
     sys.modules['importlib._bootstrap'] = _bootstrap
 
 # To simplify imports in test code

Misc/NEWS

@@ -21,6 +21,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #20884: Don't assume that __file__ is defined on importlib.__init__.
+
 - Issue #20879: Delay the initialization of encoding and decoding tables for
   base32, ascii85 and base85 codecs in the base64 module, and delay the
   initialization of the unquote_to_bytes() table of the urllib.parse module, to