python 基础之算数运算

 算术运算符

  - 示例：

  ```python
  class Number:
      def __init__(self, num):
          self.num = num

      # 对象出现在'+'的左边时会自动触发
      def __add__(self, other):
          print('__add__')
          return self.num + other

      # 对象出现在'+'的右边时会自动触发
      def __radd__(self, other):
          print('__radd__')
          return self.num + other

      # +=运算时自动触发，若没有实现会调用__add__
      def __iadd__(self, other):
          print('__iadd__')
          # 返回新的Number对象
          # return Number(self.num + other)
          # 返回处理后的原始对象
          self.num += other
          return self
      
  n = Number(10)
  print(id(n))

  # ret = n + 20
  # ret = 20 + n
  # print(ret)

  n += 50 # n = n + 50
  print(id(n))
   

有兴趣的朋友可以继续测试
 ```
  加法：add、radd、iadd
  减法：sub、rsub、isub
  乘法：mul、rmul、imul
  除法：truediv、rtruediv、itruediv
  求余：mod、rmod、imod
  ```