Python's rich comparison method __lt __, __ relationship between gt__ analysis

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Python rich comparison method comprises __lt__、__gt__respectively: less than, greater than, the corresponding operation operators are: "<", ">." Whether you like a normal number crunching, like reciprocal relationship exists between these two methods do?
Python no __lt __, __ What is the relationship between gt__ forced these two methods, but suggested __lt__ and __gt__ is reciprocal, developers can define their own needs based on business logic. Let's analyze verification:

1. When a custom class defines two methods, "<", ">", respectively, and calls __lt__ __gt__ method;
2. When a custom class defines methods __lt__, undefined __gt__ method, ">" Comparative __lt__ method is invoked, but negated recall value. Case:

>>> class Car():
   def __init__(self,carname,oilcp100km, price):
       self.carname,self.oilcp100km,self.price = carname,oilcp100km, price
   
   def __lt__(self,other):
       print("execute __lt__")
       return self.price<other.price
 >>> 
>>> car1,car2,car3,car4 = Car('爱丽舍',8,10),Car('凯美瑞',7,27),Car('爱丽舍',8,10),Car('途观',12,27)
>>> 
>>> car1>car2
execute __lt__
False
>>> car1<car2
execute __lt__
True
>>>

3. When a custom class defines methods __gt__, undefined __lt__ method, "<" Comparative __gt__ method is invoked, but negated recall value. Case:

>>> class Car():
   def __init__(self,carname,oilcp100km, price):
       self.carname,self.oilcp100km,self.price = carname,oilcp100km, price
   
     def __gt__(self,other):
       print("execute __gt__")
       return self.price>other.price

>>> car1,car2,car3,car4 = Car('爱丽舍',8,10),Car('凯美瑞',7,27),Car('爱丽舍',8,10),Car('途观',12,27)
>>> car1<car2
execute __gt__
True
>>> car1>car2
execute __gt__
False
>>>

Through the above cases, we know that when __lt __, __ when gt__ methods are defined, "<", ">", respectively call __lt__ and __gt__ method, when a definition of another undefined, undefined operations performed calls upon the already defined methods negated. This relationship with __eq__ and __ne__ still quite different.

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