What are metaclasses in Python?


In Python, a metaclass is a class that is used to create a class. When a class is defined, the class definition is passed to the metaclass, which processes it and returns a new class object. This new class object is then used to create instances of the original class. Metaclasses are used to customize the behavior of a class. They can be used to add methods or attributes to a class, or to change the way a class is created. Here is an example of how a metaclass could be used to add a method to a class:

class MyMetaclass(type):
    def __new__(cls, name, bases, dct):
        dct['say_hello'] = lambda self: "Hello, world!"
        return type.__new__(cls, name, bases, dct)

class MyClass(metaclass=MyMetaclass):
    pass

my_obj = MyClass()
my_obj.say_hello() # Output: "Hello, world!"

In this example, the MyMetaclass metaclass adds a say_hello method to the MyClass class. This method simply returns the string "Hello, world!" when called. Metaclasses are a powerful and advanced feature of Python, and their use is not common in most Python code. They can be difficult to understand and use correctly, so it is generally recommended to avoid using them unless you have a specific need for their functionality.
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