在Python中使用循环定义列表清单 [英] Defining a list of list with a loop in Python

问题描述

我正在尝试使用Python循环定义列表列表. 我要构建以下列表:

I am trying to define a list of lists with a loop in Python. I want to construct the following list:

x=[[0,0],[1,0],[2,0],...,[9,0]]

这基本上是我要做的:

x=[[0,0]]*10
for i in range(10):
    x[i][0]=i
print x

但是，我最终得到以下列表:

However, I end up with the following list:

x=[[9,0],[9,0],[9,0],...,[9,0]]

我做错了什么?非常感谢您的帮助

What am I doing wrong? Thank you so much for your help

推荐答案

您要这样做吗?

>>> [[i, 0] for i in range(10)]
[[0, 0], [1, 0], [2, 0], [3, 0], [4, 0], [5, 0], [6, 0], [7, 0], [8, 0], [9, 0]]

您这样做的问题是创建了一个列表，然后使用*并没有创建更多列表，而是只是对其进行了更多引用，这意味着每次更改列表时，列表中，您每次都更改相同列表.

What was wrong with that you were doing is that you were creating a list, and then by using the * you were not creating more, you were just making more references to it, this means that each time you changed the list, you were changing the same list each time.

>>> a = [[]]*10
>>> a
[[], [], [], [], [], [], [], [], [], []]
>>> a[0].append('X')
>>> a
[['X'], ['X'], ['X'], ['X'], ['X'], ['X'], ['X'], ['X'], ['X'], ['X']]

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