python：为多维列表赋值答案

【问题标题】：python: assign value to multiple dimensional listpython：为多维列表赋值
【发布时间】：2018-09-22 04:23:20
【问题描述】：

我有以下代码：

X = [[[None] * 4] * 2] * 6

for i in range(0, 6):
    X[i][0][0] = i

X

结果给出：

[[[5, None, None, None], [5, None, None, None]],
 [[5, None, None, None], [5, None, None, None]],
 [[5, None, None, None], [5, None, None, None]],
 [[5, None, None, None], [5, None, None, None]],
 [[5, None, None, None], [5, None, None, None]],
 [[5, None, None, None], [5, None, None, None]]]

这对我来说很奇怪，结果不应该像下面这样吗？

[[[0, None, None, None], [0, None, None, None]],
 [[1, None, None, None], [1, None, None, None]],
 [[2, None, None, None], [2, None, None, None]],
 [[3, None, None, None], [3, None, None, None]],
 [[4, None, None, None], [4, None, None, None]],
 [[5, None, None, None], [5, None, None, None]]]

我在这里错过了什么？谢谢！

【问题讨论】：

How to clone or copy a list?的可能重复
使用[[[[None] for i in range(4)] for j in range(2)] for k in range(6)] 创建您的列表。您只是在创建对同一个列表 atm 的引用。
检查容器元素的id()，你会发现它们都是同一个列表。

标签： arrays python-2.7 list

【解决方案1】：

a = [[]] * 2  # here initiated a list and assigned to a.
id(a[0]) >>> 4509460384
id(a[1]) >>> 4509460384

b = [[] for _ in range(2)]  # here constructing a list and assigning to b.
id(b[0]) >>> 4509626808
id(b[1]) >>> 4509626880

希望这一切都解决了！

【讨论】：