Use set intersection len for DictFilter. Fixes #12.

jaraco · Mar 22, 2023 · bf03fa4 · bf03fa4
1 parent 617c1d2
commit bf03fa4
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diff --git a/CHANGES.rst b/CHANGES.rst
@@ -1,3 +1,9 @@
+v3.9.0
+======
+
+``DictFilter.__len__`` no longer relies on the iterable. Improves
+efficiency and fixes ``RecursionError`` on PyPy (#12).
+
 v3.8.0
 ======
 

diff --git a/jaraco/collections.py b/jaraco/collections.py
@@ -137,7 +137,7 @@ def __iter__(self):
         return filter(self.include_keys.__contains__, self.dict.keys())
 
     def __len__(self):
-        return len(list(self))
+        return len(self.include_keys & self.dict.keys())
 
 
 def dict_map(function, dictionary):