从元组列表创建Python列表 [英] Creating a Python list from a list of tuples

问题描述

例如，如果我有一个元组列表，例如

If I have, for example, a list of tuples such as

a = [(1,2)] * 4

如何创建每个元组的第一个元素的列表?即[1, 1, 1, 1].

how would I create a list of the first element of each tuple? That is, [1, 1, 1, 1].

推荐答案

使用列表理解:

>>> a = [(1,2)] * 4
>>> [t[0] for t in a]
[1, 1, 1, 1]

您还可以打开元组的包装:

You can also unpack the tuple:

>>> [first for first,second in a]
[1, 1, 1, 1]

如果想花哨的话，请组合 map 和 operator.itemgetter .在python 3中，您必须将结构包装在list中以获取列表，而不是可迭代的列表:

If you want to get fancy, combine map and operator.itemgetter. In python 3, you'll have to wrap the construct in list to get a list instead of an iterable:

>>> import operator
>>> map(operator.itemgetter(0), a)
<map object at 0x7f3971029290>
>>> list(map(operator.itemgetter(0), a))
[1, 1, 1, 1]

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