Optimized method for calculating cosine distance in Python

Question

I wrote a method to calculate the cosine distance between two arrays:

def cosine_distance(a, b):
    if len(a) != len(b):
        return False
    numerator = 0
         


        

Answer 1

def cd(a,b):
    if(len(a)!=len(b)):
        raise ValueError, "a and b must be the same length"
    rn = range(len(a))
    adb = sum([a[k]*b[k] for k in rn])
    nma = sqrt(sum([a[k]*a[k] for k in rn]))
    nmb = sqrt(sum([b[k]*b[k] for k in rn]))

    result = 1 - adb / (nma*nmb)
    return result