Mirror
/
cpython
mirror of https://github.com/python/cpython
4
1
Fork 0
Code Issues Releases Wiki Activity

Rework multiset methods to use less memory and to make fewer calls to __hash__.

This commit is contained in:
Raymond Hettinger 2011-04-17 20:08:41 -07:00
parent c116da04a9
commit efeb8bdaa2
1 changed files with 19 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

31
Lib/collections.py
View File

@ -552,10 +552,13 @@ class Counter(dict):
if not isinstance(other, Counter): if not isinstance(other, Counter):
return NotImplemented return NotImplemented
result = Counter() result = Counter()
for elem in set(self) | set(other): for elem, count in self.items():
newcount = self[elem] + other[elem] newcount = count + other[elem]
if newcount > 0: if newcount > 0:
result[elem] = newcount result[elem] = newcount
for elem, count in other.items():
if elem not in self and count > 0:
result[elem] = count
return result return result
def __sub__(self, other): def __sub__(self, other):
@ -568,10 +571,13 @@ class Counter(dict):
if not isinstance(other, Counter): if not isinstance(other, Counter):
return NotImplemented return NotImplemented
result = Counter() result = Counter()
for elem in set(self) | set(other): for elem, count in self.items():
newcount = self[elem] - other[elem] newcount = count - other[elem]
if newcount > 0: if newcount > 0:
result[elem] = newcount result[elem] = newcount
for elem, count in other.items():
if elem not in self and count < 0:
result[elem] = 0 - count
return result return result
def __or__(self, other): def __or__(self, other):
@ -584,11 +590,14 @@ class Counter(dict):
if not isinstance(other, Counter): if not isinstance(other, Counter):
return NotImplemented return NotImplemented
result = Counter() result = Counter()
for elem in set(self) | set(other): for elem, count in self.items():
p, q = self[elem], other[elem] other_count = other[elem]
newcount = q if p < q else p newcount = other_count if count < other_count else count
if newcount > 0: if newcount > 0:
result[elem] = newcount result[elem] = newcount
for elem, count in other.items():
if elem not in self and count > 0:
result[elem] = count
return result return result
def __and__(self, other): def __and__(self, other):
@ -601,11 +610,9 @@ class Counter(dict):
if not isinstance(other, Counter): if not isinstance(other, Counter):
return NotImplemented return NotImplemented
result = Counter() result = Counter()
if len(self) < len(other): for elem, count in self.items():
self, other = other, self other_count = other[elem]
for elem in _ifilter(self.__contains__, other): newcount = count if count < other_count else other_count
p, q = self[elem], other[elem]
newcount = p if p < q else q
if newcount > 0: if newcount > 0:
result[elem] = newcount result[elem] = newcount
return result return result