20230824103843.md

Customizing Class Creation with init_subclass

In Python, the __init_subclass__() method is a powerful and lesser-known tool for customizing class creation behavior in subclasses.

Example:

class Plugin:
    plugins = []

    def __init_subclass__(cls, **kwargs):
        super().__init_subclass__(**kwargs)
        cls.plugins.append(cls)

class ConcretePlugin(Plugin):
    pass

class AnotherPlugin(Plugin):
    pass

print(Plugin.plugins)
# Output: [<class '__main__.ConcretePlugin'>, <class '__main__.AnotherPlugin'>]

📘 Plugin is a base class.

🚀 Whenever a subclass of Plugin is defined, init_subclass of Plugin is automatically called.

🔍 Inside the init_subclass method, the newly defined subclass (cls in this context) is appended to the plugins list.

✅ So, after defining the ConcretePlugin and AnotherPlugin subclasses, the plugins list contains references to these two classes.

This technique can be useful to enforce certain constraints, add class-level attributes, or perform any setup tasks 💡 💪

This feature was introduced in #Python 3.6 - PEP 487 – Simpler customisation of class creation 😎

#classes #oop