Issue #14159: Fix the len() of weak sets to return a better approximation when some objects are dead or dying.
Moreover, the implementation is now O(1) rather than O(n).
Thanks to Yury Selivanov for reporting.
diff --git a/Lib/_weakrefset.py b/Lib/_weakrefset.py
index ffa5e31..91077c5 100644
--- a/Lib/_weakrefset.py
+++ b/Lib/_weakrefset.py
@@ -63,7 +63,7 @@
yield item
def __len__(self):
- return sum(x() is not None for x in self.data)
+ return len(self.data) - len(self._pending_removals)
def __contains__(self, item):
try: