Multiple inheritance

Learn multiple inheritance and MRO.

Multiple inheritance

Multiple inheritance is when a class inherits from more than one parent. Parents are separated by commas in parentheses.

Example: class C(A, B): pass. Here C inherits from both A and B. Methods of both parents are available on a C instance. If a same-name method exists, the MRO order decides.

MRO order

MRO (Method Resolution Order) is the order in which Python searches parents. In multiple inheritance it goes left to right. You can see the order with C.mro().

Example: for class C(A, B) the MRO is [C, A, B, object]. So c.hello() is searched in C first, then A, then B. In diamond inheritance C3 linearization produces a consistent order.

Exercise Multiple inheritance C class

Define class A; add def hello(self): and in the body write print("A"). Define class B; add def hello(self): and in the body write print("B"). Then define class C(A, B): pass. Create an instance with c = C() and call c.hello().

Show example solution

# Define the A, B and C classes
class A:
    def hello(self):
        print("A")

class B:
    def hello(self):
        print("B")

class C(A, B):
    pass

c = C()
c.hello()

Test yourself

Which is a multiple inheritance definition?
- class C: pass
- class C(A, B): pass
- class C extends A, B: pass
- class C(A): pass
Show answer

class C(A, B): pass — Two parents separated by a comma show multiple inheritance.
Complete the multiple inheritance definition
```
class C(A, ____):
    pass
```
Show answer
```
class C(A, B):
    pass
```
Match the multiple inheritance concepts

class C(A, B)

Multiple inheritance
C.mro()

Resolution order
A, B

Comma parents

Next lesson: isinstance and issubclass

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