Error message from function definition

aeneng pan aeneng at gmail.com
Sat Mar 29 03:10:10 CET 2008


Dear community members,

I just start to use python in numerical calculation. and I encountered some
difficulties when I define my own function.
Here is a piece of codes to compute the cross product of two 3x1 vector.

can any one help me to find what is wrong with it? please see the codes
below.

when I import this function, it is not correct. here is the message I got.

>>> import cross
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "cross.py", line 8
    ppp2=u[2]*v[0]-u[0]*v[2]
    ^
SyntaxError: invalid syntax

Thank you very much.

Neng


##cross.py##
def cross(u,v):
    """input two vectors u and v in 3-D space, both are in column or are in
row.
    output a cross product of vector w, in column or in row accordingly.
    w=u x v. The type of u, v, w are matrix type from optcvx.base.matrix."""
    ppp1,ppp2,ppp3=0.0,0.0,0.0
    ppp1=u[1]*v[2]-u[2]*v[1]
    ppp2=u[2]*v[0]-u[0]*v[2]
    ppp3=u[0]*v[1]-u[1]*v[0]
    # store the result of the cross product in u
    u[0]=ppp1
    u[1]=ppp2
    u[2]=ppp3
    return u #return the cross product of vector u x v.
if __name__=="__main__":
    from cvxopt.base import matrix
    u=matrix([1.0,0.0,0.0],(3,1))
    v=matrix([0.0,1.0,0.0],(3,1))
    print "the cross product, uxv, is w= %6.3f" % cross(u,v)
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