Python 中的大于/小于比较

Question

When implementing the rich comparison methods in a class, what should be returned when comparing two different class types? From the documentation it says

Instances of a class cannot be ordered with respect to other instances of the same class, or other types of object, unless the class defines either enough of the rich comparison methods ( __lt__() , __le__() , __gt__() , and __ge__() ) or the __cmp__() method.

However, I can't find anywhere in the documentation where it mentions the standard return type for comparison between two different classes. I'd like to know the standard for both Python 2 and Python 3 .

Answer 1

__cmp__ ( Python 2.x only ) should return negative for self < other , zero for self == other and positive for self > other .

The others ("rich comparison methods", 2.x and 3.x) should return appropriate booleans, eg __lt__(self, other) should return True when self < other , False otherwise.