I think the speed of your pure Python version can be improved by a factor of 2..3 by making better use of some features in the standard library. Try: from

I think the speed of your pure Python version can be improved by a factor of 2..3 by making better use of some features in the standard library. Try: from math import sqrt, hypot from operator import mul def cosine_distance(a, b): dot_product = sum(map(mul, a, b)) magnitude_a = hypot(*a) magnitude_b = hypot(*b) cosine_similarity = dot_product / (magnitude_a * magnitude_b) return 1 - cosine_similarity Also check sumprod introduced in the math module from 3.12 onwards.