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('1111111111111111111111111111111111111111')

　

# 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
')
#     f.write('Georgetest
')
#     f.write('Georgetest
')
#     f.write('Georgetest
')
#     f.write('Georgetest
')


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
')
    write_file.write('123123123123123
')
    print(sssssssssssssss)
    write_file.write('123123123123123
')