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from cpython.sequence cimport PySequence_Tuple
from cytoolz.itertoolz cimport frequencies, pluck
from itertools import groupby
__all__ = ['countby', 'partitionby']
cpdef object countby(object key, object 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]) # doctest:+SKIP
{True: 1, False: 2}
See Also:
groupby
"""
if not callable(key):
return frequencies(pluck(key, seq))
return frequencies(map(key, seq))
cdef class partitionby:
""" 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
"""
def __cinit__(self, object func, object seq):
self.iter_groupby = groupby(seq, key=func)
def __iter__(self):
return self
def __next__(self):
cdef object key, val
key, val = next(self.iter_groupby)
return PySequence_Tuple(val)
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