A = [[1,2],[2,3]]
B = [[4,5],[7,8]]

ROWS_A, COLS_A = len(A), len(A[0])
ROWS_B, COLS_B = len(B), len(B[0])
assert COLS_A == ROWS_B
COMMON_D = ROWS_B

# zeros for Rows-A x Cols-B
M_TIMES = []
for r in range(ROWS_A):
    M_TIMES.append( [0] * COLS_B )

# Loop over Rows-A, then Cols-B, then the common dimension
for rA in range(ROWS_A):
    for cB in range(COLS_B):
        for t in range(COMMON_D):
            M_TIMES[rA][cB] += A[rA][t]*B[t][cB]
        print(M_TIMES[rA][cB])