I'm trying to create a 3-dimensional NNN list in Python, like such:
n=3
l = [[[0,]*n]*n]*n
Unfortunately, this does not seem to properly "clone" the list, as I thought it would:
>>> l
[[[0, 0, 0], [0, 0, 0], [0, 0, 0]], [[0, 0, 0], [0, 0, 0], [0, 0, 0]], [[0, 0, 0], [0, 0, 0], [0, 0, 0]]]
>>> l[0][0][0]=1
>>> l
[[[1, 0, 0], [1, 0, 0], [1, 0, 0]], [[1, 0, 0], [1, 0, 0], [1, 0, 0]], [[1, 0, 0], [1, 0, 0], [1, 0, 0]]]
What am I doing wrong here?
The problem is that * n
does a shallow copy of the list. A solution is to use nested loops, or try the numpy library.