[Enhancement]: Add operator replacement for operator.itemgetter and operator.attrgetter

[Skylion007]

Overview

Expand operator replacement rules with operator.itemgetter / operator.attrgetter

Proposal

Mostly people do not know that operator.itemgetter and operator.attrgetter exist. They can be often very useful especially for sorting. For example:

a = sorted(b, key=lambda x: x[1])

becomes

a = sorted(b, key=operator.itemgetter(1)

This becomes even more important in complex situations where you accessing multiple attributes or items at once. See https://stackoverflow.com/questions/11287207/why-should-i-use-operator-itemgetterx-instead-of-x for examples where it can help.

[dosisod]

I think this would be a good addition, especially if you are doing something like this:

a = sorted(b, key=lambda x: (x[3], x[2], x[1], x[0]))
# vs
a = sorted(b, key=itemgetter(3, 2, 1, 0))

One concern I have is that attrgetter("attr") won't give a Mypy error if attr happens to get renamed to something else, whereas lambda x: x.attr will give an error that attr doesn't exist anymore. I don't think this is a major problem though, since proper testing would be able to weed this out.

[Skylion007]

Yeah, they could maybe different rules then or something. itemgetter seems to have no real downsides though. I could imagine someone may want to enable the itemgetter rule, but not the attrgetter.

[dosisod]

Thank you @Skylion007 for opening this!