What is the role and purpose of a metaclass in programming languages?

A metaclass in Python is a class that creates other classes. Its role is to control the process of class creation, allowing modification or extension of class behavior at the time of their definition. Metaclasses are typically used to implement additional logic, such as automatic registration of classes, attribute validation, or inheritance modification.

Example of a simple metaclass:

class Meta(type):
    def __new__(cls, name, bases, dct):
        print(f'Creating class {name}')
        return super().__new__(cls, name, bases, dct)

class MyClass(metaclass=Meta):
    pass

When defining MyClass, it will output: Creating class MyClass.

Thus, metaclasses provide a powerful tool for metaprogramming, allowing influence over the structure and behavior of classes.