__missing__ — Expert Playground

# __missing__ with metaclasses
class AutoReprMeta(type):
    def __new__(mcs, name, bases, namespace):
        cls = super().__new__(mcs, name, bases, namespace)

        # Auto-generate __repr__ from __init__ params
        init = namespace.get("__init__")
        if init:
            import inspect
            params = list(inspect.signature(init).parameters.keys())[1:]

            def auto_repr(self):
                args = ", ".join(f"{p}={getattr(self, p)!r}" for p in params)
                return f"{type(self).__name__}({args})"

            cls.__repr__ = auto_repr

        return cls

class Point(metaclass=AutoReprMeta):
    def __init__(self, x, y):
        self.x = x
        self.y = y

class Person(metaclass=AutoReprMeta):
    def __init__(self, name, age):
        self.name = name
        self.age = age

print(Point(3, 4))
print(Person("Alice", 30))

# MRO inspection
print(f"\nMRO: {[c.__name__ for c in Point.__mro__]}")