Compute cosine similarity between two vectors

cossim.py

import math
def cosine_similarity(v1, v2):
    "compute cosine similarity of v1 to v2: (v1 dot v2)/{||v1||*||v2||)"
    sumxx, sumxy, sumyy = 0.0, 0.0, 0.0
    for i in range(len(v1)):
        x = v1[i]
        y = v2[i]
        sumxx += x * x
        sumyy += y * y
        sumxy += x * y
    return sumxy / math.sqrt(sumxx * sumyy)