# -*- coding:utf-8 -*-

 # 普通版 如果写入的过程中出错 则不会释放资源

 def m1():

     f = open("test.txt","w")

     f.write("hello python")

     f.close()

 # 进阶版

 def m2():

     f = open("test2.txt","w")

     try:

         f.write("hello python2")

     except IOError:

         print("oops error")

     finally:

         f.close()

 # 高级

 def m3():

     with open("test3.txt","w") as f:

         f.write("hello python3")

 m1()

 m2()

 m3()

 # 上下文管理器

 # 任何实现了 __enter__() 和 __exit__() 方法的对象都可称之为上下文管理器，上下文管理器对象可以使用 with 关键字。显然，文件（file）对象也实现了上下文管理器。

 class File(object):

     def __init__(self,filename,model):

         self.filename = filename

         self.model = model

     def __enter__(self):

         print("--enter--")

         self.f = open(self.filename,self.model)

         return self.f

     def __exit__(self, *args):

         print("--exit--")

         self.f.close()

 with File("test4.txt","w") as f:

     f.write("hello python4")   # 输出  --enter--

                                     # --exit - -

 # 装饰器实现上下文管理器

 from contextlib import contextmanager

 @contextmanager

 def my_open(path,model,encod):

     f = open(path,model,encoding=encod)

     yield f

     f.close()

 with my_open("test5.txt","w",'utf-8') as f:

     f.write("contextmanager实现上下文管理器")