Copying nested lists in Python

2018-06-08 20:29:04

I want to copy a 2D list, so that if I modify one list, the other is not modified.

For a one-dimensional list, I just do this:

a = [1, 2]
b = a[:]

And now if I modify b , a is not modified.

But this doesn't work for a two-dimensional list:

a = [[1, 2],[3, 4]]
b = a[:]

If I modify b , a gets modified as well.

How do I fix this?

对于一个更通用的解决方案，无论维数如何，都可以使用copy.deepcopy() ：

import copy
b = copy.deepcopy(a)

b = [x[:] for x in a]

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