When doing something like for example:

arr = [[0]*3]*3
arr[1][0] = 4

It will alter the first element in all three lists. Is this because we are only making a copy of the first list and the elements share the same pointer in memory?

That is, the first list is for example:

[A,A+C,A+2C] where C is the Offset and A is the address to the first value. And the construction above creates a list: [[A,A+C,A+2C], [A,A+C,A+2C], [A,A+C,A+2C]] Ergo, if we change any element in any position of one of the lists, we alter the corresponding the the other lists?