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：

 1 import time
 2 class Open:
 3     def __init__(self,filepath,mode='r',encode='utf-8'):
 4         self.f=open(filepath,mode=mode,encoding=encode)
 5 
 6     def write(self):
 7         pass
 8 
 9     def __getattr__(self, item):
10         return getattr(self.f,item)
11 
12     def __del__(self):
13         print('----->del')
14         self.f.close()
15 
16 f=Open('a.txt','w')
17 f1=f
18 del f
19 
20 print('=========>')

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　　上下文管理协议：　

 1 # with open('a.txt','r') as f:
 2 #     print('--=---->')
 3 #     print(f.read())
 4 
 5 # with open('a.txt', 'r'):
 6 #     print('--=---->')
 7 
 8 
 9 #
10 class Foo:
11     def __enter__(self):
12         print('=======================》enter')
13         return 111111111111111
14 
15     def __exit__(self, exc_type, exc_val, exc_tb):
16         print('exit')
17         print('exc_type',exc_type)
18         print('exc_val',exc_val)
19         print('exc_tb',exc_tb)
20         return True
21 
22 
23 # with Foo(): #res=Foo().__enter__()
24 #     pass
25 
26 with Foo() as obj: #res=Foo().__enter__() #obj=res
27     print('with foo的自代码块',obj)
28     raise NameError('名字没有定义')
29     print('************************************')
30 
31 print('1111111111111111111111111111111111111111')

View Code

　

 1 # import time
 2 # class Open:
 3 #     def __init__(self,filepath,mode='r',encode='utf-8'):
 4 #         self.f=open(filepath,mode=mode,encoding=encode)
 5 
 6 #     def write(self,line):
 7 #         self.f.write(line)
 8 
 9 
10 #     def __getattr__(self, item):
11 #         return getattr(self.f,item)
12 
13 #     def __del__(self):
14 #         print('----->del')
15 #         self.f.close()
16 
17 #     def __enter__(self):
18 #         return self.f
19 #     def __exit__(self, exc_type, exc_val, exc_tb):
20 #         self.f.close()
21 
22 
23 # with Open('George'.txt','w') as f:
24 #     f.write('Georgetest\n')
25 #     f.write('Georgetest\n')
26 #     f.write('Georgetest\n')
27 #     f.write('Georgetest\n')
28 #     f.write('Georgetest\n')
29 
30 
31 class Open:
32     def __init__(self,filepath,mode,encode='utf-8'):
33         self.f=open(filepath,mode=mode,encoding=encode)
34         self.filepath=filepath
35         self.mode=mode
36         self.encoding=encode
37 
38     def write(self,line):
39         print('write')
40         self.f.write(line)
41 
42     def __getattr__(self, item):
43         return getattr(self.f,item)
44 
45     def __enter__(self):
46         return self
47 
48     def __exit__(self, exc_type, exc_val, exc_tb):
49         self.f.close()
50         return True
51 
52 with Open('aaaaa.txt','w') as write_file: #write_file=Open('aaaaa.txt','w')
53     write_file.write('123123123123123\n')
54     write_file.write('123123123123123\n')
55     print(sssssssssssssss)
56     write_file.write('123123123123123\n')

View Code