What is MRO and how does it work?

MRO (Method Resolution Order) is the order in which Python searches for methods and attributes in a class hierarchy during inheritance, especially in the case of multiple inheritance.

Python uses the C3 linearization algorithm to compute the MRO. It guarantees that:

• Each class appears in the MRO after its parents.
• The method search order is unambiguous and predictable.

For example, if class C inherits from A and B, the MRO determines the order in which Python will search for methods: first in C, then in A, then in B, or vice versa, depending on the hierarchy.

Example:

class A:
    def method(self):
        print("A")

class B(A):
    def method(self):
        print("B")

class C(A):
    def method(self):
        print("C")

class D(B, C):
    pass

print(D.mro())  # Shows the method search order
D().method()    # Will print "B" because B comes before C in the MRO

Thus, MRO helps avoid ambiguities when calling methods in complex inheritance hierarchies.