Making a python user-defined class sortable, hashable

Question

What methods need to be overridden/implemented when making user-defined classes sortable and/or hashable in python?

What are the gotchas to watch out for?

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Answer 1

I almost posted this as a comment to the other answers but it's really an answer in and of itself.

To make your items sortable, they only need to implement __lt__. That's the only method used by the built in sort.

The other comparisons or functools.total_ordering are only needed if you actually want to use the comparison operators with your class.

To make your items hashable, you implement __hash__ as others noted. You should also implement __eq__ in a compatible way -- items that are equivalent should hash the same.