Why should I use operator.itemgetter(x) instead of [x]?

Question

There is a more general question here: In what situation should the built-in operator module be used in python?

The top answer claims that operator.itemgetter(

Answer 1

Leaving aside performance and code style, itemgetter is picklable, while lambda is not. This is important if the function needs to be saved, or passed between processes (typically as part of a larger object). In the following example, replacing itemgetter with lambda will result in a PicklingError.

from operator import itemgetter

def sort_by_key(sequence, key):
    return sorted(sequence, key=key)

if __name__ == "__main__":
    from multiprocessing import Pool

    items = [([(1,2),(4,1)], itemgetter(1)),
             ([(5,3),(2,7)], itemgetter(0))]

    with Pool(5) as p:
        result = p.starmap(sort_by_key, items)
    print(result)