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| author | Raymond Hettinger <python@rcn.com> | 2009-01-22 09:09:55 (GMT) |
|---|---|---|
| committer | Raymond Hettinger <python@rcn.com> | 2009-01-22 09:09:55 (GMT) |
| commit | dd01f8f37b98af090098495200107dfaf92a3162 (patch) | |
| tree | 18c0b16d82372a0fd8ffbbafbf70ef18536dda3a /Lib | |
| parent | 94adc8e4b54d6532dd8a4b265133d4105b96ea7a (diff) | |
| download | cpython-dd01f8f37b98af090098495200107dfaf92a3162.zip cpython-dd01f8f37b98af090098495200107dfaf92a3162.tar.gz cpython-dd01f8f37b98af090098495200107dfaf92a3162.tar.bz2 | |
Update comments and add an optimized path for Counter.update().
Diffstat (limited to 'Lib')
| -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 232c772..6831cf1 100644 --- a/Lib/collections.py +++ b/Lib/collections.py @@ -255,8 +255,11 @@ class Counter(dict): if iterable is not None: if isinstance(iterable, Mapping): - for elem, count in iterable.items(): - self[elem] += count + if self: + for elem, count in iterable.items(): + self[elem] += count + else: + dict.update(self, iterable) # fast path when counter is empty else: for elem in iterable: self[elem] += 1 @@ -282,7 +285,6 @@ 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: |