m = 5
n = 3
a = [[0 for x in range(n)] for y in range(m)]
Or a shorter version:
a = [[0]*n for y in range(m)]
Note: shortening this to something like the following does not really work since you end up with 5 copies of the same list, so when you modify one of them, they all change.
a = [[0]*n]*m
print(a)
a[1][2] = 3
print(a)
[[0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 0], [0, 0, 0]]
[[0, 0, 3], [0, 0, 3], [0, 0, 3], [0, 0, 3], [0, 0, 3]]
You can use [0] * n since Python cannot create a reference to the value 0(it's not an object) and this produces [0,0,0]. Then if you pretend you had a variable x = [0,0,0] then
c1 = x * 5
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
c2 = [x] * 5
[[0, 0, 0], [0, 0, 3], [0, 0, 0], [0, 0, 0], [0, 0, 0]]
[[0, 22, 0], [0, 22, 0], [0, 22, 0], [0, 22, 0], [0, 22, 0]]
