python - 获取元组列表的第一个索引？

Question

返回以下内容的最简洁方法是什么:

给定一个元组列表,返回一个由元组组成的列表(或者第二个,无关紧要).

对于:

[(1,'one'),(2,'two'),(3,'three')]

返回的列表将是

[1,2,3]

Answer 1

如果你需要两个,请使用zip

>>> r=(1,'one'),(2,'two'),(3,'three')
>>> zip(*r)
[(1, 2, 3), ('one', 'two', 'three')]

Answer 2

>>> tl = [(1,'one'),(2,'two'),(3,'three')]
>>> [item[0] for item in tl]
[1, 2, 3]

Answer 3

>>> mylist = [(1,'one'),(2,'two'),(3,'three')]
>>> [j for i,j in mylist]
['one', 'two', 'three']
>>> [i for i,j in mylist]
[1, 2, 3]

这是使用列表理解(看看这个链接).因此,它依次遍历元素mylist,设置i和j元组中的两个元素.它实际上相当于:

>>> newlist = []
>>> for i, j in mylist:
...     newlist.append(i)
... 
>>> newlist
[1, 2, 3]