10.3 Defining classes with total ordering

The @total_ordering decorator is helpful for creating new class definitions that implement a rich set of comparison operators. This might apply to numeric classes that subclass numbers.Number. It may also apply to semi-numeric classes.

As an example of a semi-numeric class, consider a playing card. It has a numeric rank and a symbolic suit. The suit, for example, may not matter for some games. Like ordinary integers, cards have an ordering. We often sum the point values of each card, making them number-like. However, multiplication of cards, card × card, doesn’t really make any sense; a card isn’t quite like a number.

We can almost emulate a playing card with a NamedTuple base class as follows:

from typing import NamedTuple 
 
class Card1(NamedTuple): 
    rank: int 
    suit: str

This model suffers from a profound limitation: all comparisons between cards will include...