46 – Dot product idiom

The dot product is a mathematical operation that can be computed with a simple Python idiom using the module operator:

import operator

sum(map(operator.mul, vec1, vec2))

The snippet above assumes vec1 and vec2 are iterables that represent vectors. This idiom was present in the documentation of the module itertools up to Python 3.11.

Then, in Python 3.12, the built-in zip got the keyword argument strict, which made the idiom evolve into something that looks a bit more complicated:

from itertools import starmap
import operator

sum(starmap(operator.mul, zip(vec1, vec2, strict=True)))

We’re using zip(..., strict=True) to ensure the vectors have the same size and zip produces tuples, so starmap is being used to “unpack” that tuple into the two arguments to operator.mul.

Then, in Python 3.14, the built-in map got a similar keyword argument strict, which means the idiom can go back to its simpler form with the extra safety check:

import operator

sum(map(operator.mul, vec1, vec2, strict=True))