异常处理

异常捕获

1. try-expect 语句

   i = input("请输入一个非零十进制数: ")
   y = 123
   
   try:
       result = y / int(i)
       print(result)
       print("{0} / {1} = {2}".format(y, i, result))
   except ZeroDivisionError as e1:
       print("异常: {}".format(e1))
   except ValueError as e2:
       print("异常: {}".format(e2))
       
   # 多重异常捕获, 合并相同的处理:
   # except (ZeroDivisionError, ValueError) as e:
   #     print("异常: {}".format(e))
   #
   # 最后省略异常类型的except代码块用来捕获上面没有匹配的异常类.
   # except:
   #     print("某种异常")
   
   finally:  # 释放资源
       print("资源释放...")
   

2. 语句嵌套

   i = input("请输入一个非零十进制数: ")
   y = 123
   
   try:
       i2 = int(i)
       try:
           result = y / i2
           print("{0} / {1} = {2}".format(y, i2, result))
       except ZeroDivisionError as e2:
           print("异常: {}".format(e2))
   except ValueError as e1:
       print("异常: {}".format(e1))
   finally:  # 释放资源
       print("资源释放...")
   

自定义异常类

class CE(Exception):
    def __init__(self, message):
        super().__init__(message)

手动引发异常

• raise

  class CE(Exception):
      def __init__(self, message):
          super().__init__(message)
          
          
  i = input("请输入一个非零十进制数: ")
  y = 123
  
  try:
      result = y/int(i)
      print("{0} / {1} = {2}".format(y, i, result))
  except ZeroDivisionError as e1:
      raise CE("除数为零!")
  except ValueError as e2:
      raise CE("无效数字!")
      
  # 请输入一个非零十进制数: 0
  # Traceback (most recent call last):
  #   File "F:\day12_.py", line 10, in <module>
  #     result = y / int(i)
  # ZeroDivisionError: division by zero
  # 
  # During handling of the above exception, another exception occurred:
  # 
  # Traceback (most recent call last):
  #   File "F:\day12_.py", line 13, in <module>
  #     raise CE("除数为零!")
  # __main__.CE: 除数为零!