Introduction

Python supports multiple inheritance, allowing a class to inherit from more than one parent. But with this flexibility comes complexity — especially when two parent classes define the same attribute. Suppose both class X and class Y define an attribute named value, and a third class Z inherits from both. Which value will Z use? More importantly, how can you ensure that Z always uses the value from class Y?

Let’s explore how Python’s Method Resolution Order (MRO) handles this — and how you can control it.

Mid Section: Understanding and Solving the Conflict

Let’s start with a basic example:

class X:
    value = "X's value"

class Y:
    value = "Y's value"

class Z(X, Y):
    pass

print(Z.value)  # Output: X's value

Here, Python uses the attribute from X because X appears before Y in the inheritance list of Z. Python follows MRO, which means it searches for attributes from left to right in the class definition.

Method 1: Change the Inheritance Order

Method 1: Change the Inheritance Order

To make Z use Y‘s value, you can simply change the order of inheritance:

class Z(Y, X):
    pass

print(Z.value)  # Output: Y's value

This works because now Y is searched before X.

Method 2: Override the Attribute in Z

If changing the inheritance order isn’t an option (e.g., due to existing architecture or behavior dependencies), you can override the attribute in Z directly using Y.value:

class Z(X, Y):
    value = Y.value

print(Z.value)  # Output: Y's value

This explicitly tells Python to use the value defined in class Y, no matter the order of inheritance.

Conclusion

Multiple inheritance offers power but requires careful control, especially when parent classes share attribute names. By understanding Python’s MRO and using techniques like adjusting inheritance order or overriding attributes manually, you can ensure that your code behaves exactly as intended. In the case of value, whether it comes from X or Y is up to you — Python just needs clear instructions.