python with 用法

G8bao7發表於2015-10-26
Python


點選(此處)摺疊或開啟

  1. #!/usr/bin/env python
  2. #coding=utf8

  4. import sys

  6. '''
  7. must implement method '__enter__' and '__exit__'. same as
  8. try:
  9.     __enter__
  10.     block
  11. finally:
  12.     __exit__
  13. '''
  14. class WithCls():
  15.     # execute before run block
  16.     # 可以不定義引數 *args
  17.     def __enter__(self, *args):
  18.         print("%s(%s) called " % (sys._getframe().f_code.co_name, args))
  19.         res = True
  20.         return res

  22.     # 當block發生 異常、錯誤、exit等情況時呼叫
  23.     # 必須定義 *args，接收異常等資訊
  24.     def __exit__(self, *args):
  25.         print("%s(%s) called " % (sys._getframe().f_code.co_name,args))
  26.         # raise exception
  27.         res = False
  28.         # not raise exception
  29.         res = True
  30.         return res

  32. # t = __enter__， 可以不加t
  33. with WithCls() as t:
  34.     print("t is not the result of WithCls(), it is __enter__ returned")
  35.     # will call __exit__, and exit
  36.     raise NameError("Hi there")
  37.     print("Never here")

  39.     exit(0)



參考:
http://blog.csdn.net/shuimuniao/article/details/8206812


來自 “ ITPUB部落格 ” ，連結：http://blog.itpub.net/26250550/viewspace-1816342/，如需轉載，請註明出處，否則將追究法律責任。

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