Python: bind method outside loop to reduce overhead

Came across this interesting pattern in some of the sklearn codebase:

        # bind method outside of loop to reduce overhead
        ngrams_append = ngrams.append

        for n in range(min_n, min(max_n + 1, text_len + 1)):
            for i in range(text_len - n + 1):
                ngrams_append(text_document[i: i + n])
        return ngrams

 

I wonder, at what scale does this really start to make a meaningful performance difference?

Even if it doesn’t make a huge difference, I do find it pretty elegant and easy to follow.