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Improve all_equal() recipe (gh-116081)

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Replace conjuction of next() calls with simpler len()/take() logic. Add key function.
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Raymond Hettinger 2024-02-28 17:04:56 -06:00 committed by GitHub
parent 81c79961d2
commit 67c19e57b5
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1 changed files with 4 additions and 3 deletions
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7
Doc/library/itertools.rst
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@ -863,10 +863,9 @@ which incur interpreter overhead.
"Given a predicate that returns True or False, count the True results."
return sum(map(pred, iterable))
def all_equal(iterable):
def all_equal(iterable, key=None):
"Returns True if all the elements are equal to each other."
g = groupby(iterable)
return next(g, True) and not next(g, False)
return len(take(2, groupby(iterable, key))) <= 1
def first_true(iterable, default=False, pred=None):
"""Returns the first true value in the iterable.
@ -1225,6 +1224,8 @@ The following recipes have a more mathematical flavor:
>>> [all_equal(s) for s in ('', 'A', 'AAAA', 'AAAB', 'AAABA')]
[True, True, True, False, False]
>>> [all_equal(s, key=str.casefold) for s in ('', 'A', 'AaAa', 'AAAB', 'AAABA')]
[True, True, True, False, False]
>>> quantify(range(99), lambda x: x%2==0)
50