def produkt(a, b):
    """Produkt matrik a in b"""
    # a ima dimenzije k x m
    k = len(a)
    m = len(a[0])
    # b ima dimenzije m x n
    assert (m == len(b))
    n = len(b[0])
    # assert javi napako, če pogoj in izpoljen
    c = [[0 for j in range(n)] for i in range(k)]
    for i in range(k):
        for j in range(n):
            for l in range(m):
                c[i][j] += a[i][l] * b[l][j]
    return c

print(produkt(
    [[1,2,3],
     [3,4,5]],
    [[1, 0],
     [1, 1],
     [0, 1]]
))