Python 类例子

下面有个银行账号的例子，我们要确保没人能设置金额为负，并且有个只读属性 cny 返回换算人名币后的金额。

#!/usr/bin/env python3

class Account(object):
  def __init__(self, rate):
    self.__amt = 0
    self.rate = rate

  @property
  def amount(self):
    return self.__amt

  @property
  def cny(self):
    return self.__amt * self.rate

  @amount.setter
  def amount(self, value):
    if value < 0:
      print('Sorry, no negative amount in the account.')
      return 
self.__amt = value


if __name__ == '__main__':
  acc = Account(rate = 6.6)
  acc.amount = 20
  print('Dollar amount:', acc.amount)
  print('IN CNY:', acc.cny)
  acc.amount = -100
  print('Dollar amount:', acc.amount)