Extension of inheriting from namedtuple

tclass.py

def tclass(*argnames, then_do=None):
    if len(argnames) == 1 and isinstance(argnames[0], dict):
        argnames = argnames[0]

    def decorator(cls):
        def inner_init(self, *args, **kwargs):
            for argname, arg in zip(argnames, args):
                self.__setattr__(argname, arg)
            for argname in list(argnames)[len(args):]:
                self.__setattr__(argname, argnames[argname])
            # Doesn't check for multiple values
            self.__dict__.update(kwargs)
            if then_do:
                self.__getattribute__(then_do)()

        def inner_repr(self):
            reprargs = (repr(self.__getattribute__(argname)) for argname in argnames)
            return '{}({})'.format(cls.__name__, ', '.join(reprargs))
        cls.__init__ = inner_init
        cls.__repr__ = inner_repr
        return cls
    return decorator


@tclass('x', 'y', then_do='post_init')
class Point:
    def post_init(self):
        self.length = (self.x ** 2 + self.y ** 2) ** 0.5

print(repr(Point(1, 2)))
print(repr(Point(3, 4)))
print(Point(3, 4).length)

@tclass({'size': 'small', 'empty': True})
class Box:
    pass

print(repr(Box()))
print(repr(Box(empty=False)))
print(repr(Box('medium')))
print(repr(Box('large', False)))

"""
Point(1, 2)
Box('small', True)
Box('small', False)
Box('medium', True)
Box('large', False)
"""

tclass_simplified.py

from collections import namedtuple

def tclass(argnames, then_do=None):
    def decorator(cls):
        class inner(namedtuple('inner', argnames), cls):
            def __init__(self, *args, **kwargs):
                cls.__init__(*args, **kwargs)
                if then_do:
                    self.__getattribute__(then_do)(*args, **kwargs)
        return inner
    return decorator

@tclass('x y', then_do='post_init')
class Point:
    def post_init(self, x, y):
        self.length = (x ** 2 + y ** 2) ** 0.5

print(repr(Point(1, 2)))
print(repr(Point(3, 4)))
print(Point(3, 4).length)