What’s the point of inheritance in Python?

Question

Suppose you have the following situation

#include 

class Animal {
public:
    virtual void speak() = 0;
};

class Dog : public Animal {
             


        

Answer 1

Classes in Python are basically just ways of grouping a bunch of functions and data.. They are different to classes in C++ and such..

I've mostly seen inheritance used for overriding methods of the super-class. For example, perhaps a more Python'ish use of inheritance would be..

from world.animals import Dog

class Cat(Dog):
    def speak(self):
        print "meow"

Of course cats aren't a type of dog, but I have this (third party) Dog class which works perfectly, except the speak method which I want to override - this saves re-implementing the entire class, just so it meows. Again, while Cat isn't a type of Dog, but a cat does inherit a lot of attributes..

A much better (practical) example of overriding a method or attribute is how you change the user-agent for urllib. You basically subclass urllib.FancyURLopener and change the version attribute (from the documentation):

import urllib

class AppURLopener(urllib.FancyURLopener):
    version = "App/1.7"

urllib._urlopener = AppURLopener()

Another manner exceptions are used is for Exceptions, when inheritance is used in a more "proper" way:

class AnimalError(Exception):
    pass

class AnimalBrokenLegError(AnimalError):
    pass

class AnimalSickError(AnimalError):
    pass

..you can then catch AnimalError to catch all exceptions which inherit from it, or a specific one like AnimalBrokenLegError