Python中的异常处理学习笔记

def div(num, den):
 print('_________________   (',num,',',den,')\n')
 try:
  ans = num/den
  assert den != num, 'Equal' # 断言：分子分母不相等
  den = 'Changed'            # 如果执行本语句之前未出现异常，改变 den 的值
  if num % 2:                # 如果分子为奇数，则抛出异常
   raise ValueError('Odd')
 except ZeroDivisionError as e:
  print('except ... as ...\n\t', e)
 except:
  print('except\n\t', sys.exc_info())
 else:
  print('else\n\t', ans)
 finally:
  print('finally\n\t', den)

div(1,0) # 除数为零，为 ZeroDivisionError 异常类
div(1,1) # 分子等于分母，断言为假，抛出异常
div(2,1) # 无异常
div(3,1) # 分子为奇数，通过 raise 抛出异常
div(3,'x') # 不属于 ZeroDivisionError 的其他异常

except ... as ...
  division by zero
finally
  0
_________________   ( 1 , 1 )

except
  (<class 'AssertionError'>, AssertionError('Equal',), <traceback object at 0x00000000029B42C8>)
finally
  1
_________________   ( 2 , 1 )

else
  2.0
finally
  Changed
_________________   ( 3 , 1 )

except
  (<class 'ValueError'>, ValueError('Odd',), <traceback object at 0x00000000029B42C8>)
finally
  Changed
_________________   ( 3 , x )

except
  (<class 'TypeError'>, TypeError("unsupported operand type(s) for /: 'int' and 'str'",), <traceback object at 0x00000000029B42C8>)
finally
  x