Issue #23509: Speed up Counter operators
(Based on patch by Serhiy Storchaka.)
diff --git a/Lib/collections/__init__.py b/Lib/collections/__init__.py
index 6794de1..80dc4f6 100644
--- a/Lib/collections/__init__.py
+++ b/Lib/collections/__init__.py
@@ -753,14 +753,22 @@
def __pos__(self):
'Adds an empty counter, effectively stripping negative and zero counts'
- return self + Counter()
+ result = Counter()
+ for elem, count in self.items():
+ if count > 0:
+ result[elem] = count
+ return result
def __neg__(self):
'''Subtracts from an empty counter. Strips positive and zero counts,
and flips the sign on negative counts.
'''
- return Counter() - self
+ result = Counter()
+ for elem, count in self.items():
+ if count < 0:
+ result[elem] = 0 - count
+ return result
def _keep_positive(self):
'''Internal method to strip elements with a negative or zero count'''