Python异常继承关系和自定义异常实现代码实例

BaseException # 所有异常的基类
 +-- SystemExit # 解释器请求退出
 +-- KeyboardInterrupt  用户中断执行(通常是输入^C)
 +-- GeneratorExit # 生成器(generator)发生异常来通知退出
 +-- Exception # 常规异常的基类
  +-- StopIteration # 迭代器没有更多的值
  +-- StandardError # 标准错误
  | +-- BufferError
  | +-- ArithmeticError
  | | +-- FloatingPointError
  | | +-- OverflowError
  | | +-- ZeroDivisionError
  | +-- AssertionError
  | +-- AttributeError
  | +-- EnvironmentError
  | | +-- IOError
  | | +-- OSError
  | |   +-- WindowsError (Windows)
  | |   +-- VMSError (VMS)
  | +-- EOFError
  | +-- ImportError
  | +-- LookupError
  | | +-- IndexError
  | | +-- KeyError
  | +-- MemoryError
  | +-- NameError
  | | +-- UnboundLocalError
  | +-- ReferenceError
  | +-- RuntimeError
  | | +-- NotImplementedError
  | +-- SyntaxError
  | | +-- IndentationError
  | |   +-- TabError
  | +-- SystemError
  | +-- TypeError
  | +-- ValueError
  |   +-- UnicodeError
  |    +-- UnicodeDecodeError
  |    +-- UnicodeEncodeError
  |    +-- UnicodeTranslateError
  +-- Warning
   +-- DeprecationWarning
   +-- PendingDeprecationWarning
   +-- RuntimeWarning
   +-- SyntaxWarning
   +-- UserWarning
   +-- FutureWarnin
   +-- ImportWarnin
   +-- UnicodeWarnin
   +-- BytesWarning

#自定义异常 需要继承Exception
class MyException(Exception):

 def __init__(self, *args):
  self.args = args

if __name__ == '__main__':
 try:
  raise MyException("自定义异常")
 except MyException as e:
  print e

# 示例
str1 = 'abc'
try:
 int(str1)
except IndexError as e:
 print e
except KeyError as e:
 print e
except ValueError as e:
 print e
else:
 print 'try内正常处理'
finally:
 print '无论异常与否,都会执行我'

# raise xxx
def test_zero(num):
 try:
  if num == 0:
   raise ValueError('参数错误')
  return num
 except Exception as e:
  print e

test_zero(0)

#示例
def div(num1, num2):
 try:
  result = num1/num2
  return result
 except Exception as e:
  traceback.print_exc()

print div(1, 0)

#执行结果
Traceback (most recent call last):
None
 File "F:/Technology-20161005/python/python_project/demo/exceptiondemo/exceptiondemo.py", line 17, in div
 result = num1/num2
ZeroDivisionError: integer division or modulo by zero

# 可以将异常信息写到文件中
traceback.print_exc(file=open('1.txt','w+'))