是否有一个类似zip的函数可以在Python中填充最长的长度? [英] Is there a zip-like function that pads to longest length in Python?

问题描述

是否有一个内置函数，其功能类似于 zip() ，但这将填充结果，以便结果列表的长度是最长输入的长度，而不是最短输入的长度?

Is there a built-in function that works like zip() but that will pad the results so that the length of the resultant list is the length of the longest input rather than the shortest input?

>>> a = ['a1']
>>> b = ['b1', 'b2', 'b3']
>>> c = ['c1', 'c2']

>>> zip(a, b, c)
[('a1', 'b1', 'c1')]

>>> What command goes here?
[('a1', 'b1', 'c1'), (None, 'b2', 'c2'), (None, 'b3', None)]

推荐答案

在Python 3中，您可以使用 itertools.zip_longest

In Python 3 you can use itertools.zip_longest

>>> list(itertools.zip_longest(a, b, c))
[('a1', 'b1', 'c1'), (None, 'b2', 'c2'), (None, 'b3', None)]

您可以使用fillvalue参数用不同于None的值进行填充:

You can pad with a different value than None by using the fillvalue parameter:

>>> list(itertools.zip_longest(a, b, c, fillvalue='foo'))
[('a1', 'b1', 'c1'), ('foo', 'b2', 'c2'), ('foo', 'b3', 'foo')]

使用Python 2，您可以使用 itertools.izip_longest (Python 2.6+)，或者您可以将map与None结合使用.它是map 的功能(但map在Python 3.x中进行了更改，因此仅在Python 2.x中有效.

With Python 2 you can either use itertools.izip_longest (Python 2.6+), or you can use map with None. It is a little known feature of map (but map changed in Python 3.x, so this only works in Python 2.x).

>>> map(None, a, b, c)
[('a1', 'b1', 'c1'), (None, 'b2', 'c2'), (None, 'b3', None)]

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