How Should I Call Parent Class Constructors in Python Multiple Inheritance?

Determining the Correct Approach to Calling Parent Class Constructors in Multiple Inheritance

Multiple inheritance in Python necessitates proper handling to ensure that constructors of all parent classes are invoked correctly. The approach depends on the nature of the parent classes:

Unrelated Standalone Classes

If the parent classes are not designed for multiple inheritance, they will not call super().__init__(). In this case, you must manually call each parent constructor using either ParentClass.__init__(self) or super().__init__(). The latter method supports dependency injection but may lead to errors if the parent class ordering is modified.

Mixins

Mixins are classes specifically designed for multiple inheritance. They automatically call the constructor of the next class in the inheritance hierarchy. You only need to call super().__init__() in the subclass to invoke all parent constructors. Remember to inherit from the mixin first to ensure its constructor is always called.

Cooperative Inheritance Classes

Classes designed for cooperative inheritance also forward unused arguments to the next class. Similar to mixins, you can call super().__init__() in the subclass to chain-call all parent constructors, regardless of the order of inherited classes. Cooperative classes typically use keyword arguments to avoid potential issues with positional arguments.

Therefore, the correct approach for calling parent class constructors in multiple inheritance depends on the design of the parent classes. If no documentation is available, assume they are not designed for multiple inheritance and handle constructor calls manually.

The above is the detailed content of How Should I Call Parent Class Constructors in Python Multiple Inheritance?. For more information, please follow other related articles on the PHP Chinese website!