From bbe2f60b3c19ecaa02ca07be14474eaacfcb59a0 Mon Sep 17 00:00:00 2001
From: Antoine Pitrou <solipsis@pitrou.net>
Date: Thu, 1 Mar 2012 16:26:35 +0100
Subject: Issue #14159: Fix the len() of weak containers (WeakSet,
 WeakKeyDictionary, WeakValueDictionary) 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.

---
 Lib/_weakrefset.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'Lib/_weakrefset.py')

diff --git a/Lib/_weakrefset.py b/Lib/_weakrefset.py
index 42653699a3..f34aa864bc 100644
--- a/Lib/_weakrefset.py
+++ b/Lib/_weakrefset.py
@@ -63,7 +63,7 @@ class WeakSet:
                     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:
-- 
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