python property demo

property_example.py

#!/usr/bin/env python
# -*- coding: UTF-8 -*-
'''
zhihu question demo: https://www.zhihu.com/question/55594368
'''

class Mat(object):
    """动态读，class 内部只存 temp 的值，每次取 pro 的时候实时计算"""
    def __init__(self, t):
        self.temp = t

    @property
    def pro(self):
        return self.temp * self.temp


a = Mat(5)
print(a.temp, a.pro)  # (5, 25)
a.temp = 10
print(a.temp, a.pro)  # (10, 100)


class Mat2(object):
    """两个都存，写入的时候两个都改"""
    def __init__(self, t):
        self.temp = t

    @property
    def temp(self):
        return self._temp

    @temp.setter
    def temp(self, v):
        self._temp = v
        self.pro = self.Pro(v)

    def Pro(self, t):
        return t * t


a = Mat2(5)
print(a.temp, a.pro)  # (5, 25)
a.temp = 10
print(a.temp, a.pro)  # (10, 100)