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61 lines
1.6 KiB
61 lines
1.6 KiB
from cpython.sequence cimport PySequence_Tuple
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from cytoolz.itertoolz cimport frequencies, pluck
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from itertools import groupby
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from cytoolz.compatibility import map
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__all__ = ['countby', 'partitionby']
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cpdef object countby(object key, object seq):
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"""
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Count elements of a collection by a key function
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>>> countby(len, ['cat', 'mouse', 'dog'])
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{3: 2, 5: 1}
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>>> def iseven(x): return x % 2 == 0
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>>> countby(iseven, [1, 2, 3]) # doctest:+SKIP
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{True: 1, False: 2}
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See Also:
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groupby
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"""
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if not callable(key):
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return frequencies(pluck(key, seq))
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return frequencies(map(key, seq))
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cdef class partitionby:
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""" partitionby(func, seq)
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Partition a sequence according to a function
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Partition `s` into a sequence of lists such that, when traversing
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`s`, every time the output of `func` changes a new list is started
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and that and subsequent items are collected into that list.
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>>> is_space = lambda c: c == " "
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>>> list(partitionby(is_space, "I have space"))
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[('I',), (' ',), ('h', 'a', 'v', 'e'), (' ',), ('s', 'p', 'a', 'c', 'e')]
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>>> is_large = lambda x: x > 10
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>>> list(partitionby(is_large, [1, 2, 1, 99, 88, 33, 99, -1, 5]))
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[(1, 2, 1), (99, 88, 33, 99), (-1, 5)]
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See also:
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partition
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groupby
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itertools.groupby
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"""
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def __cinit__(self, object func, object seq):
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self.iter_groupby = groupby(seq, key=func)
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def __iter__(self):
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return self
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def __next__(self):
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cdef object key, val
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key, val = next(self.iter_groupby)
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return PySequence_Tuple(val)
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