python exception handling try except else finally raise

python exception handling try except else finally raise

Purpose: To prevent the code from crashing due to exceptions during operation, an exception handling mechanism is added to keep the program running normally

format

try: 
	执行的代码
except:
	发生异常时执行的代码
else:
	没有异常时执行的代码
finally:
	不管有没有异常都会执行的代码

Note:

• There can only be one try, multiple except, and none and finally

• except 的形式：
      except:
      except ValueError:
      except ValueError as e:
      except Exception as e:

• Get information about a specific exception:

  try:
  	1/0
  except Exception as e:
  	print(e.args)   # ('division by zero',)
  	print(str(e))   # division by zero
  	print(repr(e))	# ZeroDivisionError('division by zero')
  

• Manually throw an exception raise:

  a = int(input('input a:'))
  b = int(input('input b:'))
  if b==0 :
      raise ZeroDivisionError  # ZeroDivisionError
      # raise  # RuntimeError: No active exception to reraise
      # raise ZeroDivisionError('除数不能为零')  # ZeroDivisionError: 除数不能为零
  else:
      print(a/b)