>>> class Rectangle(object):
...   def __init__(self, length, width):
...     self.length = length
...     self.width = width
...   def area(self):
...     return self.length * self.width
...   @property
...   def area_p(self):
...     return self.length * self.width
... 
>>> r = Rectangle(100, 500)
>>> r.area()
50000
>>> r.area_p
50000