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In-depth discussion of the multiple inheritance mechanism in Python
Introduction:
In Python, multiple inheritance is a powerful and flexible mechanism. Through multiple inheritance, we can integrate the attributes and methods of multiple parent classes into one class at the same time, which greatly enhances the functionality of the class.
Sample code 1:
class A: def method_a(self): print("This is method A") class B: def method_b(self): print("This is method B") class C(A, B): def method_c(self): print("This is method C") obj = C() obj.method_a() # Output: This is method A obj.method_b() # Output: This is method B obj.method_c() # Output: This is method C
In the above code, we have defined three classes A, B and C. Classes A and B have two methods, method_a and method_b respectively, while class C inherits both classes A and B. In the instance obj of C, the methods of A and B can be called at the same time.
Sample code 2:
class A: def method(self): print("This is method A") class B(A): def method(self): print("This is method B") class C(A): def method(self): print("This is method C") class D(B, C): pass obj = D() obj.method() # Output: This is method B
In the above code, class A has a method named method, class B and class C respectively inherit class A and override The method of the parent class. Class D inherits both classes B and C. When the method method of instance obj of D is called, the method found first, that is, the method method in class B, will be called according to the method resolution order (D -> B -> C -> A).
Sample code 3:
class A: def method(self): print("This is method A") class B(A): def method(self): super().method() print("This is method B") class C(A): def method(self): super().method() print("This is method C") class D(B, C): def method(self): super().method() print("This is method D") obj = D() obj.method() # Output: This is method A # This is method C # This is method B # This is method D
In the above code, use the super().method() statement to call the method method of the parent class. Since the order of MRO is D -> B -> C -> A, when the method of class D is called, the method methods of classes A, C, B and D will be called in order.
Conclusion:
Multiple inheritance is a powerful and flexible mechanism in Python, which allows a subclass to inherit the properties and methods of multiple parent classes. By rationally using multiple inheritance, we can better organize the code and improve the reusability and maintainability of the code. At the same time, understanding the method resolution order and the use of the super() function in multiple inheritance can help us better understand and apply the multiple inheritance mechanism.
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