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from numpy import matrixfrom numpy import dotfrom numpy import arraydef mult(a,b):    c=a.copy()    c[0][0]=dot(a[0][0],b[0][0])+dot(a[0][1],b[1][0])    c[0][1]=dot(a[0][0],b[0][1])+dot(a[0][1],b[1][1])    c[1][0]=dot(a[1][0],b[0][0])+dot(a[1][1],b[1][0])    c[1][1]=dot(a[1][0],b[0][1])+dot(a[1][1],b[1][1])    return c        if __name__ == '__main__':    a=array([[+1+2j,+3+4j],             [-3+4j,+1-2j]])    b=array([[+4+3j,+2+1j],             [-2+1j,+4-3j]])    c=array([[+5+4j,+1+2j],             [-1+2j,+5-4j]])     d=array([[+6+7j,+4+2j],             [-4+2j,+6-7j]])    i=array([[1,0],[0,1]])    z=array([[0,0],[0,0]])    A=array([[a,b],[c,d]])    B=array([[c,a],[b,c]])    C=array([[a,d],[a,c]])    I=array([[i,z],[z,i]])    print "j"    print mult(A,mult(B,C))-mult(mult(A,B),C)