Diamond Problem in Python

Diamond problem is also known as the "Deadly Diamond of Death", This problem mainly occurs in object-oriented programming in Python. It mainly arises when a class inherits from two or more classes that themselves share a common superclass. This situation creates ambiguity in the inheritance hierarchy, leading to confusion about which properties or methods of the shared superclass should be inherited.

In this article, we will understand What is Diamond Problem in Python and How we can solve this problem.

Diamond Shape inheritance

• Shape: The common superclass representing general properties and behaviors of a shape.
• Circle: Intermediate subclasses that inherit from Shape, each adding specialized attributes or behaviors
• Square: Intermediate subclasses that inherit from Shape, each adding specialized attributes or behaviors.
• Cylinder: A subclass that inherits from both Circle and Square, potentially combining their attributes and behaviors.

Here's how this hierarchy looks in Python:

class shape:
    def display(self):
        print("class shape")

class circle(shape):
    def display(self):
        print("class circle")

class square(shape):
    def display(self):
        print("class square")

class cylinder(circle, square):
    pass

obj = cylinder()
obj.display()  # Calls circle's display method

class circle

Explanation:

• The given code does not give Diamond Problem in python because the python resolves multiple inheritance dispute using the Method Resolution order in short we can call it MRO .

Problem caused by Diamond Pattern

The diamond problem in Python is a problem that can occur when a class inherits from multiple classes that share a common ancestor:

• Ambiguity : If Cylinder calls a method or accesses an attribute from Shape, it is unclear whether to use the version inherited through Circle or Square.
• Duplication : When both subclasses are called , they may both call the base class method, resulting in duplicate calls.

Solving Diamond problem in Python

Python uses method resolution Order (MRO). The MRO provides a clear and consistent sequence in which classes are searched for methods or attributes, ensuring no ambiguity. The MRO is computed using the C3 Linearization Algorithm, which respects the order of inheritance while avoiding duplication.

Example of how python handles Diamond problem

Using Method Resolution order:

Python addresses the Diamond Problem by using the Method Resolution Order (MRO). The MRO ensures that methods are resolved in a predictable and consistent order, eliminating ambiguity and duplication.

class Shape:
    def draw(self):
        print("class shape")

class Circle(Shape):
    def draw(self):
        print("class circle")

class Square(Shape):
    def draw(self):
        print("class square")

class Cylinder(Circle, Square):
    pass

obj = Cylinder()
obj.draw()  # Resolves using the MRO
print(Cylinder.mro())  # Displays the MRO

class circle
[<class '__main__.Cylinder'>, <class '__main__.Circle'>, <class '__main__.Square'>, <class '__main__.Shape'>, <class 'object'>]

Using Super():

Python's super() function works with the MRO to ensure that methods in a diamond hierarchy are called in a predictable order. This allows cooperative behavior among classes.

class shape:
    def greet(self):
        print("class shape called")

class circle(shape):
    def greet(self):
        super().greet()
        print("class circle called")

class square(shape):
    def greet(self):
        super().greet()
        print("class square called")

class cylinder(circle, square):
    def greet(self):
        super().greet()
        print("class cylinder called")

d = cylinder()
d.greet()

class shape called
class square called
class circle called
class cylinder called

Explanation:

• The super() function respects the MRO, ensuring the correct order of method calls.