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| author | Raymond Hettinger <python@rcn.com> | 2009-01-22 09:05:43 (GMT) |
|---|---|---|
| committer | Raymond Hettinger <python@rcn.com> | 2009-01-22 09:05:43 (GMT) |
| commit | 1bc1c8ac766e62116bd9d677712c59d681e44c0e (patch) | |
| tree | cb1344203d3102f9d2c1cbd14c1fa9c703069dce | |
| parent | 7bdca05a3b4dd0e3cd607d35ee597e8ed177b850 (diff) | |
| download | cpython-1bc1c8ac766e62116bd9d677712c59d681e44c0e.zip cpython-1bc1c8ac766e62116bd9d677712c59d681e44c0e.tar.gz cpython-1bc1c8ac766e62116bd9d677712c59d681e44c0e.tar.bz2 | |
Update comments and add an optimized path for Counter.update().
| -rw-r--r-- | Lib/collections.py | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/Lib/collections.py b/Lib/collections.py index eb13f4d2..effae7d 100644 --- a/Lib/collections.py +++ b/Lib/collections.py @@ -253,8 +253,11 @@ class Counter(dict): if iterable is not None: if isinstance(iterable, Mapping): - for elem, count in iterable.iteritems(): - self[elem] += count + if self: + for elem, count in iterable.iteritems(): + self[elem] += count + else: + dict.update(self, iterable) # fast path when counter is empty else: for elem in iterable: self[elem] += 1 @@ -280,7 +283,6 @@ class Counter(dict): # Knuth TAOCP Volume II section 4.6.3 exercise 19 # and at http://en.wikipedia.org/wiki/Multiset # - # Results are undefined when inputs contain negative counts. # Outputs guaranteed to only include positive counts. # # To strip negative and zero counts, add-in an empty counter: |