[docs] [issue27212] Doc for itertools, 'islice()' implementation have unwanted behavior for recipe 'consume()'

[Raymond Hettinger]

Raymond Hettinger added the comment:

The recipe should be modified to consume the initial values.  Something like this:

    start, stop, step = s.start or 0, s.stop or sys.maxsize, s.step or 1
    for i in zip(range(0, start), it):
        pass

The recipe needs to pass these tests:

    it = iter('abcdefghi')
    assert list(islice(it, 4, 4)) == []
    assert list(it) == ['e', 'f', 'g', 'h', 'i']
    assert(list(islice('ABCDEFG', 2)) == ['A', 'B'])
    assert(list(islice('ABCDEFG', 2, 4)) == ['C', 'D'])
    assert(list(islice('ABCDEFG', 2, None)) == ['C', 'D', 'E', 'F', 'G'])
    assert(list(islice('ABCDEFG', 0, None, 2)) == ['A', 'C', 'E', 'G'])

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue27212>
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