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

When using this in the key parameter of sorted() or min(), given the choice between say operator.itemgetter(1) and lambda x: x[1], the former is typically significantly faster in both cases:

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Using sorted()

The compared functions are defined as follows:

import operator


def sort_key_itemgetter(items, key=1):
    return sorted(items, key=operator.itemgetter(key))


def sort_key_lambda(items, key=1):
    return sorted(items, key=lambda x: x[key])

Result: sort_key_itemgetter() is faster by ~10% to ~15%.

(Full analysis here)

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Using min()

The compared functions are defined as follows:

import operator


def min_key_itemgetter(items, key=1):
    return min(items, key=operator.itemgetter(key))


def min_key_lambda(items, key=1):
    return min(items, key=lambda x: x[key])

Result: min_key_itemgetter() is faster by ~20% to ~60%.

(Full analysis here)