[Python]同步上下文管理

'''
同步上下文管理器
'''

import time


class ContextManager:
    def __init__(self):
        self.conn = None

    def action(self):
        return self.conn


def __enter__(self):  # 链接数据库
    print("开始连接")
    time.sleep(1)
    self.conn = "OK"
    return self


def __exit__(self, exc_type, exc, tb):  # 关闭数据库链接
    print("关闭连接")
    self.conn = "CLOSE"


def main():
    with ContextManager() as cm:
        result = cm.action()
        print(result)


main()