contextmanager.py

import contextlib
@contextlib.contextmanager
def open_func(file_name):
    # __enter__方法
    print('open file:', file_name, 'in __enter__')
    file_handler = open(file_name, 'r')

    yield file_handler

    # __exit__方法
    print('close file:', file_name, 'in __exit__')
    file_handler.close()
    return