Python之面向对象上下文管理协议

Python之面向对象上下文管理协议

　　析构函数：

 import time
 class Open:
     def __init__(self,filepath,mode='r',encode='utf-8'):
         self.f=open(filepath,mode=mode,encoding=encode)

     def write(self):
         pass

     def __getattr__(self, item):
         return getattr(self.f,item)

     def __del__(self):
         print('----->del')
         self.f.close()

 f=Open('a.txt','w')
 f1=f
 del f

 print('=========>')

　　上下文管理协议：　

 # with open('a.txt','r') as f:
 #     print('--=---->')
 #     print(f.read())

 # with open('a.txt', 'r'):
 #     print('--=---->')

 #
 class Foo:
     def __enter__(self):
         print('=======================》enter')
         return 111111111111111

     def __exit__(self, exc_type, exc_val, exc_tb):
         print('exit')
         print('exc_type',exc_type)
         print('exc_val',exc_val)
         print('exc_tb',exc_tb)
         return True

 # with Foo(): #res=Foo().__enter__()
 #     pass

 with Foo() as obj: #res=Foo().__enter__() #obj=res
     print('with foo的自代码块',obj)
     raise NameError('名字没有定义')
     print('************************************')

 print('')

　

 # import time
 # class Open:
 #     def __init__(self,filepath,mode='r',encode='utf-8'):
 #         self.f=open(filepath,mode=mode,encoding=encode)

 #     def write(self,line):
 #         self.f.write(line)

 #     def __getattr__(self, item):
 #         return getattr(self.f,item)

 #     def __del__(self):
 #         print('----->del')
 #         self.f.close()

 #     def __enter__(self):
 #         return self.f
 #     def __exit__(self, exc_type, exc_val, exc_tb):
 #         self.f.close()

 # with Open('George'.txt','w') as f:
 #     f.write('Georgetest\n')
 #     f.write('Georgetest\n')
 #     f.write('Georgetest\n')
 #     f.write('Georgetest\n')
 #     f.write('Georgetest\n')

 class Open:
     def __init__(self,filepath,mode,encode='utf-8'):
         self.f=open(filepath,mode=mode,encoding=encode)
         self.filepath=filepath
         self.mode=mode
         self.encoding=encode

     def write(self,line):
         print('write')
         self.f.write(line)

     def __getattr__(self, item):
         return getattr(self.f,item)

     def __enter__(self):
         return self

     def __exit__(self, exc_type, exc_val, exc_tb):
         self.f.close()
         return True

 with Open('aaaaa.txt','w') as write_file: #write_file=Open('aaaaa.txt','w')
     write_file.write('123123123123123\n')
     write_file.write('123123123123123\n')
     print(sssssssssssssss)
     write_file.write('123123123123123\n')