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

There are a few ways of marking your object sortable. First - rich comparison, defined by a set of functions:

object.__lt__(self, other)
object.__le__(self, other)
object.__eq__(self, other)
object.__ne__(self, other)
object.__gt__(self, other)
object.__ge__(self, other)

Also it is possible to define only one function:

object.__cmp__(self, other)

And the last should be defined if you want to define custom __hash__ function. See the doc.