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authorRaymond Hettinger <python@rcn.com>2015-05-30 05:14:07 (GMT)
committerRaymond Hettinger <python@rcn.com>2015-05-30 05:14:07 (GMT)
commit4c97a62ae34a0e892755a8f95ae6e11881d6feb3 (patch)
tree2e1c65ed65c929a6341884b50d74067e90d7a641 /Lib/collections
parent3d1151d2c000e22a90038d8fb4d77cf22430bcab (diff)
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Issue #23509: Speed up Counter operators
(Based on patch by Serhiy Storchaka.)
Diffstat (limited to 'Lib/collections')
-rw-r--r--Lib/collections/__init__.py12
1 files changed, 10 insertions, 2 deletions
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 @@ class Counter(dict):
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'''