Python 标准库——itertools

一、chain / chain.from_iterable

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二、izip / imap / starmap

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三、count / cycle / repeat

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四、ifilter/ islice

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五、compress / dropwhile / takewhile

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六、groupby

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七、produce / permutations / combinations

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参考：

[1] https://docs.python.org/2.7/library/itertools.html#module-itertools
[2] https://pymotw.com/2/itertools/index.html