Do you have experience using metaclasses in your projects?

Yes, I have experience using metaclasses, although they were not frequently used in projects, mainly for solving specific tasks.

Metaclasses in Python allow controlling the creation of classes, for example, automatically registering classes, checking their attributes, or modifying behavior.

An example of using a metaclass to register all subclasses in a dictionary:

class RegistryMeta(type):
    registry = {}

    def __new__(cls, name, bases, attrs):
        new_class = super().__new__(cls, name, bases, attrs)
        cls.registry[name] = new_class
        return new_class

class Base(metaclass=RegistryMeta):
    pass

class A(Base):
    pass

class B(Base):
    pass

print(RegistryMeta.registry)

This is useful, for example, for plugins or factories where you need to work dynamically with classes.