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Issue #18652: Add an itertools recipe for first_true()

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This commit is contained in:
Raymond Hettinger 2014-04-02 03:16:42 -07:00
parent f4284e45d0
commit 31b26f637a
2 changed files with 29 additions and 0 deletions
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16
Lib/test/test_itertools.py
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@ -1998,6 +1998,19 @@ Samuele
... # unique_justseen('ABBCcAD', str.lower) --> A B C A D
... return map(next, map(itemgetter(1), groupby(iterable, key)))
>>> def first_true(iterable, default=False, pred=None):
... '''Returns the first true value in the iterable.
...
... If no true value is found, returns *default*
...
... If *pred* is not None, returns the first item
... for which pred(item) is true.
...
... '''
... # first_true([a,b,c], x) --> a or b or c or x
... # first_true([a,b], x, f) --> a if f(a) else b if f(b) else x
... return next(filter(pred, iterable), default)
This is not part of the examples but it tests to make sure the definitions
perform as purported.
@ -2075,6 +2088,9 @@ True
>>> list(unique_justseen('ABBCcAD', str.lower))
['A', 'B', 'C', 'A', 'D']
>>> first_true('ABC0DEF1', '9', str.isdigit)
'0'
"""
__test__ = {'libreftest' : libreftest}