You probably want:
[[] for _ in range(n)]
Unlike [[]] * n
, this will give you unique inner lists (appending to one doesn't append to them all). e.g.:
>>> x = [[] for _ in range(n)]
>>> x[0].append(1)
>>> x
[[1], [], []]
compared to:
>>> x = [[]] * 3
>>> x[0].append(1)
>>> x
[[1], [1], [1]]
Note that this latter idiom ([[]] * n
) is a very common mistake that crops up around here in different contexts pretty frequently.