A class that implements an ordering operator (__lt__, __gt__, __le__ or __ge__) should implement all four in order that ordering between two objects is consistent and obeys the usual mathematical rules. If the ordering is inconsistent with default equality, then __eq__ and __ne__ should also be implemented.

Ensure that all four ordering comparisons are implemented as well as __eq__ and __ne__ if required.

It is not necessary to manually implement all four comparisons, the functools.total_ordering class decorator can be used.

In this example only the __lt__ operator has been implemented which could lead to inconsistent behavior. __gt__, __le__, __ge__, and in this case, __eq__ and __ne__ should be implemented.

Python Language Reference: Rich comparisons in Python.