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Document another recipe for itertools: all_equal(). Inspired by David Beazley.

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Raymond Hettinger 2016-03-06 18:11:38 -08:00
parent d66dd5ce68
commit e525ee3b48
2 changed files with 13 additions and 0 deletions
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5
Doc/library/itertools.rst
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@ -693,6 +693,11 @@ which incur interpreter overhead.
"Returns the nth item or a default value" "Returns the nth item or a default value"
return next(islice(iterable, n, None), default) return next(islice(iterable, n, None), default)
def all_equal(iterable):
"Returns True if all the elements are equal to each other"
g = groupby(iterable)
return next(g, True) and not next(g, False)
def quantify(iterable, pred=bool): def quantify(iterable, pred=bool):
"Count how many times the predicate is true" "Count how many times the predicate is true"
return sum(map(pred, iterable)) return sum(map(pred, iterable))

8
Lib/test/test_itertools.py
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@ -2014,6 +2014,11 @@ Samuele
... "Returns the nth item or a default value" ... "Returns the nth item or a default value"
... return next(islice(iterable, n, None), default) ... return next(islice(iterable, n, None), default)
>>> def all_equal(iterable):
... "Returns True if all the elements are equal to each other"
... g = groupby(iterable)
... return next(g, True) and not next(g, False)
>>> def quantify(iterable, pred=bool): >>> def quantify(iterable, pred=bool):
... "Count how many times the predicate is true" ... "Count how many times the predicate is true"
... return sum(map(pred, iterable)) ... return sum(map(pred, iterable))
@ -2127,6 +2132,9 @@ perform as purported.
>>> nth('abcde', 9) is None >>> nth('abcde', 9) is None
True True
>>> [all_equal(s) for s in ('', 'A', 'AAAA', 'AAAB', 'AAABA')]
[True, True, True, False, False]
>>> quantify(range(99), lambda x: x%2==0) >>> quantify(range(99), lambda x: x%2==0)
50 50