Presented FreezableDefaultDict from jaraco.collections. Keep inline to minimize dependencies.

Author: jaraco

importlib_metadata/__init__.py

@@ -14,7 +14,7 @@
 import contextlib
 import collections
 
-from ._collections import freezable_defaultdict
+from ._collections import FreezableDefaultDict
 from ._compat import (
     NullFinder,
     Protocol,
@@ -659,8 +659,8 @@ class Lookup:
     def __init__(self, path: FastPath):
         base = os.path.basename(path.root).lower()
         base_is_egg = base.endswith(".egg")
-        self.infos = freezable_defaultdict(list)
-        self.eggs = freezable_defaultdict(list)
+        self.infos = FreezableDefaultDict(list)
+        self.eggs = FreezableDefaultDict(list)
 
         for child in path.children():
             low = child.lower()

importlib_metadata/_collections.py

@@ -1,11 +1,14 @@
 import collections
 
 
-class freezable_defaultdict(collections.defaultdict):
+# from jaraco.collections 3.3
+class FreezableDefaultDict(collections.defaultdict):
     """
-    Mix-in to freeze a defaultdict.
+    Often it is desirable to prevent the mutation of
+    a default dict after its initial construction, such
+    as to prevent mutation during iteration.
 
-    >>> dd = freezable_defaultdict(list)
+    >>> dd = FreezableDefaultDict(list)
     >>> dd[0].append('1')
     >>> dd.freeze()
     >>> dd[1]