Инициализация членов класса для ленивых

gistfile1.py

#!/usr/bin/python
import inspect
from functools import wraps

class SimpleInitializationMixin(object):
    def __new__(cls, *args, **kwargs):
        obj = super(SimpleInitializationMixin, cls).__new__(cls, *args, **kwargs)

        func_signature = inspect.getargspec(cls.__init__)
        defaults = [None] * (len(func_signature.args) - len(func_signature.defaults)) + list(func_signature.defaults)
        args_spec = list(reversed(zip(func_signature.args, defaults)))

        args_spec.pop()  # ignore 'self' argument

        for value in args:
            if not args_spec:
                break
            name, _ = args_spec.pop()
            setattr(obj, name, value)

        for name, default in args_spec:
            setattr(obj, name, kwargs.get(name, default))

        return obj




def simple_initialization(func):
    @wraps(func)
    def wrapper(obj, *args, **kwargs):
        func_signature = inspect.getargspec(func)
        defaults = [None] * (len(func_signature.args) - len(func_signature.defaults)) + list(func_signature.defaults)
        args_spec = list(reversed(zip(func_signature.args, defaults)))

        args_spec.pop()  # ignore 'self' argument

        for value in args:
            if not args_spec:
                break
            name, _ = args_spec.pop()
            setattr(obj, name, value)

        for name, default in args_spec:
            setattr(obj, name, kwargs.get(name, default))

        func(obj, *args, **kwargs)

    return wrapper


class MyClass1(SimpleInitializationMixin):
    def __init__(self, one='one', two='two', three=None, four=None):
        pass


class MyClass2(object):
    @simple_initialization
    def __init__(self, one='one', two='two', three=None, four=None):
        pass

def main():
    for cls in (MyClass1, MyClass2):
        obj = cls(one='111')
        assert not hasattr(obj, 'self')
        assert obj.one == '111'
        assert obj.two == 'two'
        assert obj.three == None
        assert obj.four == None


        obj = cls()
        assert obj.one == 'one'
        assert obj.two == 'two'
        assert obj.three == None
        assert obj.four == None

        obj = cls(1,2,3,4)
        assert obj.one == 1
        assert obj.two == 2
        assert obj.three == 3
        assert obj.four == 4


if __name__ == '__main__':
    main()