本来想着简单点，用列表乘法

        输出也看了一下，没啥问题

[[0, 0, 0], [0, 0, 0], [0, 0, 0]]

        输出就变得奇怪了

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。

[[0, 0, 0], [0, 0, 0], [0, 0, 0]] [[4, 0, 0], [0, 0, 0], [0, 0, 0]]

[[0, 0, 0], [0, 0, 0], [0, 0, 0]] [[4, 0, 0], [4, 0, 0], [4, 0, 0]]