Question

I asked a question about initializing a 2 dimensional array yesterday, this is the link:
How to implement this C++ source in python?

There is a problem in the answer, a friend mentioned a way:

G = [[0]*11]*11

But in this way, when I change the G[0][0] to 2, all the G[i][0](0<=i<11) will all change to 2, but I don’t know why?

Supplement:

This is what I thought:
The 0 or other number is immutable, so we change one of them, the others will not be changed.
But the list [0, 0 ,0 ,…..] is mutable, so when we [0, 0, …] * 11, all the [0, 0, …] list will be the same, as is function is True. am I right?

Answer 1

Because you have 11 references to the same list.

G = [[0] * 11 for x in range(11)]