How Should I Call Parent Class `__init__` Methods in Multiple Inheritance?

Calling Parent Class init with Multiple Inheritance: Understanding the Nuances

Challenge:

In multiple inheritance scenarios, determining the correct method to call parent class constructors can be a challenge. Old-style ParentClass.__init__(self) and newer-style super(DerivedClass, self).__init__() approaches have their shortcomings when parent classes follow inconsistent conventions.

Solution:

The proper approach depends on the designs of the base classes involved:

1. Unrelated Standalone Classes:

• These classes are not designed for multiple inheritance.
• Call each parent constructor manually using explicit calls or super with careful consideration of argument passing.

2. Mixin Classes:

• Designed explicitly for multiple inheritance.
• Automatically call the second parent constructor on behalf of the subclass.
• Use super().__init__() within the mixin to pass on any unused arguments.

3. Cooperative Inheritance Classes:

• Similar to mixins, with a design that allows for cooperative inheritance.
• Pass on all unused arguments to the superclass constructor.
• Use keyword arguments for all arguments to avoid positional argument ordering issues.

Important Note:

If the base classes do not explicitly mention their design for inheritance, it is safe to assume they are not designed for cooperative inheritance. Stick to explicit constructor calls or super with ParentClass.__init__(self) for consistency and clarity.

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