Python成语链接(展平)有限迭代的无限迭代? [英] Python idiom to chain (flatten) an infinite iterable of finite iterables?

问题描述

假设我们有一个返回列表(或有限迭代器)的迭代器(无限迭代器)，例如由

Suppose we have an iterator (an infinite one) that returns lists (or finite iterators), for example one returned by

infinite = itertools.cycle([[1,2,3]])

什么是获得迭代器(显然是无限的)的一个好的 Python 习惯用法，它将从第一个迭代器返回每个元素，然后从第二个迭代器返回每个元素，依此类推.在上面的示例中，它将返回 1，2,3,1,2,3,....迭代器是无限的，所以 itertools.chain(*infinite) 不起作用.

What is a good Python idiom to get an iterator (obviously infinite) that will return each of the elements from the first iterator, then each from the second one, etc. In the example above it would return 1,2,3,1,2,3,.... The iterator is infinite, so itertools.chain(*infinite) will not work.

• 扁平化python中的浅表

推荐答案

从 Python 2.6 开始，您可以使用 itertools.chain.from_iterable:

Starting with Python 2.6, you can use itertools.chain.from_iterable:

itertools.chain.from_iterable(iterables)

您也可以使用嵌套生成器推导来做到这一点:

You can also do this with a nested generator comprehension:

def flatten(iterables):
    return (elem for iterable in iterables for elem in iterable)

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