python异常处理

1、捕获，处理异常
 try:
      a = 1/0
      b = test
except AttributeError as e: 
    print str(e)
except ZerovisitionError as e: 
    print str(e) 
finally:
   print 111


 2、抛异常:
raise AttributeError('属性不存在') 


3、with替代文件操作频繁的开、关
一般麻烦情况:

try:

    f = open('aa.txt','w')

    test = f.read()

except IOError as e:

    print('io:',e)

finally:

    print('close')

    f.close()

with情况不需要关闭，他自己会帮你关闭

try:

    with open('bb.txt','w') as f:

       test = f.read()

except IOError as e:

    print(e)