descriptor

>>> class Integer:
...     def __init__(self, name):
...             self.name = name
...     def __get__(self, instance, cls):
...             return instance.__dict__[self.name]
...     def __set__(self, instance, value):
...             if not isinstance(value, int):
...                     raise TypeError('Expected int')
...             instance.__dict__[self.name] = value
... 
>>>
>>> class Point:
...     x = Integer('x')
...     def __init__(self, x):
...             self.x = x
... 
>>> p = Point(2)
>>> p.x
2
>>> p.x = 1.2
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 8, in __set__
TypeError: Expected int
>>>