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python/수학/3x4 행렬 곱하기 2010/01/30

python/수학/3x4 행렬 곱하기

Posted at 2010/01/30 19:45// Posted in python/pymath


def dot(A, B):
        sum = 0
        for a, b in zip(A, B):
                sum += a * b

        print "dot(%s, %s) = %d" % (A, B, sum)
        return sum

def mul3x4(A, B):
        out = [
                [None for x in xrange(4)]
                        for y in xrange(3)]

        for c in xrange(4):
                B_col = [B[y][c] for y in xrange(3)]
                for r, A_row in enumerate(A):
                        out[r][c] = dot(A_row, B_col)

        return out

a = [
 [2, -3, 1],
 [1, 1, -1],
 [-1, 1, -3]]

b = [
 [ 2, 6,  0, 1],
 [-1, 4,  1, 0],
 [ 0, 5, -3, 0]]

print mul3x4(a, b)