Python数组构造的坑

今天写Python代码的时候遇到了一个大坑
问题是这样的，我需要创建一个二维数组，如下：

m = n = 3
test = [[0] * m] * n
print("test =", test)

输出结果如下：

test = [[0, 0, 0], [0, 0, 0], [0, 0, 0]]

是不是看起来没有一点问题？
一开始我也是这么觉得的，以为是我其他地方用错了什么函数，结果这么一试：

m = n = 3
test = [[0] * m] * n
print("test =", test)

test[0][0] = 233
print("test =", test)

输出结果如下：

test = [[0, 0, 0], [0, 0, 0], [0, 0, 0]]
test = [[233, 0, 0], [233, 0, 0], [233, 0, 0]]

是不是很惊讶？！
这个问题真的是折磨，去网上一搜，官方文档中给出的说明是这样的：

Note also that the copies are shallow; nested structures are not
copied. This often haunts new Python programmers; consider:

lists = [[]] * 3 lists [[], [], []] lists[0].append(3) lists [[3],
[3], [3]] What has happened is that [[]] is a one-element list
containing an empty list, so all three elements of [[]] * 3 are
(pointers to) this single empty list. Modifying any of the elements of
lists modifies this single list. You can create a list of different
lists this way:

lists = [[] for i in range(3)] lists[0].append(3)
lists[1].append(5) lists[2].append(7) lists [[3], [5], [7]]

也就是说matrix = [array] * 3操作中，只是创建3个指向array的引用，所以一旦array改变，matrix中3个list也会随之改变。

建议使用列表生成式来构造list