#!/usr/bin/env python3

-- coding: utf-8 --

class Screen(object): @property def width(self): return self._width

@width.setter
def width(self,value):
    if isinstance(value,int) and value>0:
        self._width=value
    else:
        print('width is illegal')

@property
def height(self):
    return self._height

@height.setter
def height(self,value):
    if isinstance(value,int) and value>0:
        self._height=value
    else:
        print('height is illagal')

@property
def resolution(self):
    if hasattr(self,'width') and hasattr(self,'height'):
        return self._width * self._height
    else:
        print('please define all attributes')

s=Screen() s.width=1024 s.height=768 print(s.resolution)