Python - 如何按每个列表中的第四个元素对列表列表进行排序？
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Python - How to sort a list of lists by the fourth element in each list?
提问by Dana Gray
I would like to sort the following list of lists by the fourth element (the integer) in each individual list.
我想按每个单独列表中的第四个元素（整数）对以下列表列表进行排序。
unsorted_list = [['a','b','c','5','d'],['e','f','g','3','h'],['i','j','k','4','m']]
How can I do this? Thank you!
我怎样才能做到这一点？谢谢！
回答by Taymon
unsorted_list.sort(key=lambda x: x[3])
回答by Sukrit Kalra
Use sorted()with a keyas follows -
使用sorted()具有key如下-
>>> unsorted_list = [['a','b','c','5','d'],['e','f','g','3','h'],['i','j','k','4','m']]
>>> sorted(unsorted_list, key = lambda x: int(x[3]))
[['e', 'f', 'g', '3', 'h'], ['i', 'j', 'k', '4', 'm'], ['a', 'b', 'c', '5', 'd']]
The lambdareturns the fourth element of each of the inner lists and the sortedfunction uses that to sort those list. This assumes that int(elem)will not fail for the list.
所述lambda返回每个内部列表和的第四元件sorted函数使用排序那些列表。这假设int(elem)列表不会失败。
Or use itemgetter(As Ashwini's comment pointed out, this method would not work if you have string representations of the numbers, since they are bound to fail somewhere for 2+ digit numbers)
或使用itemgetter（正如 Ashwini 的评论所指出的，如果您有数字的字符串表示形式，则此方法将不起作用，因为对于 2 位以上的数字，它们肯定会在某处失败）
>>> from operator import itemgetter
>>> sorted(unsorted_list, key = itemgetter(3))
[['e', 'f', 'g', '3', 'h'], ['i', 'j', 'k', '4', 'm'], ['a', 'b', 'c', '5', 'd']]
