Python: 练习 with语句和上下文管理器 __enter__() 和 __exit__()方法 @contextmanager 装饰器

from contextlib import contextmanager


class OpenFile(object):
    def __init__(self, file, mode='r', buffering=None, encoding=None, errors=None, newline=None, closefd=True):
        self.file = file
        self.mode = mode

    def __enter__(self):
        print("OpenFileA上文方法")
        self.fd = open(self.file, self.mode)
        return self.fd

    def __exit__(self, exc_type, exc_val, exc_tb):
        print("OpenFileA下文方法")
        self.fd.close()


@contextmanager
def open_file(file, mode='r', buffering=None, encoding=None, errors=None, newline=None, closefd=True):
    print("open_file上文方法")
    fd = open(file, mode)
    yield fd
    print("open_file下文方法")
    fd.close()

with OpenFile("test.py", "r") as fd:
    print(fd.read())
with open_file("test.py", "r") as fd:
    print(fd.read())