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Expand the implementation comments (GH-19699)

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Raymond Hettinger 2020-04-24 02:33:07 -07:00 committed by GitHub
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7
Lib/collections/__init__.py
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@ -711,6 +711,13 @@ class Counter(dict):
# #
# To strip negative and zero counts, add-in an empty counter: # To strip negative and zero counts, add-in an empty counter:
# c += Counter() # c += Counter()
#
# Rich comparison operators for multiset subset and superset tests
# are deliberately omitted due to semantic conflicts with the
# existing inherited dict equality method. Subset and superset
# semantics ignore zero counts and require that p≤q ∧ p≥q → p=q;
# however, that would not be the case for p=Counter(a=1, b=0)
# and q=Counter(a=1) where the dictionaries are not equal.
def __add__(self, other): def __add__(self, other):
'''Add counts from two counters. '''Add counts from two counters.