From 944db38cb720b511aad5d7850dec71402e7e2725 Mon Sep 17 00:00:00 2001 From: Raymond Hettinger Date: Tue, 26 May 2015 10:35:15 -0700 Subject: Issue #23509: Speed up Counter operators (Based on patch by Serhiy Storchaka.) --- Lib/collections/__init__.py | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/Lib/collections/__init__.py b/Lib/collections/__init__.py index fc60e13..9c22d86 100644 --- a/Lib/collections/__init__.py +++ b/Lib/collections/__init__.py @@ -736,14 +736,22 @@ 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''' -- cgit v0.12