Why you shouldn't mess with __dict__

class A(object):
    def __init__(self, **kwargs):
        self._b ='Default'
        self.__dict__.update(kwargs)

    @property
    def b(self):
        return self._b

    @b.setter
    def b(self, value):
        self._b = value

a = A(b=1, c=2)
print a.b, a.c