recipes
Functions
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Count elements of a collection by a key function |
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Partition a sequence according to a function |
- countby(key, seq)
Count elements of a collection by a key function
>>> countby(len, ['cat', 'mouse', 'dog']) {3: 2, 5: 1}
>>> def iseven(x): return x % 2 == 0 >>> countby(iseven, [1, 2, 3]) {True: 1, False: 2}
See also
groupby
- partitionby(func, seq)
Partition a sequence according to a function
Partition s into a sequence of lists such that, when traversing s, every time the output of func changes a new list is started and that and subsequent items are collected into that list.
>>> is_space = lambda c: c == " " >>> list(partitionby(is_space, "I have space")) [('I',), (' ',), ('h', 'a', 'v', 'e'), (' ',), ('s', 'p', 'a', 'c', 'e')]
>>> is_large = lambda x: x > 10 >>> list(partitionby(is_large, [1, 2, 1, 99, 88, 33, 99, -1, 5])) [(1, 2, 1), (99, 88, 33, 99), (-1, 5)]
See also
partition groupby itertools.groupby