1. Python的with这个关键字用来对context进行管理
  • 进入的时候自动持有
  • 出去的时候自动释放
class MyContextManager:
    def __enter__(self):
        print('1. entering')
        # 返回给 as 关键字
        return self
 
    def __exit__(self, exc_type, exc_val, exc_tb):
        print('3. exit...')
 
 
if __name__ == "__main__":
    with MyContextManager() as context:
        print('2. inward')
 
 
""" 
output:
1. entering
2. inward
3. exit...
"""