with open as f原理解析
1.with语句的原理:
1.1with是对类进行操作,必须包括以下三个函数
1.1.1 def __enter__(self):return self 必须返回自己
1.1.2 def __exit__(self, exc_type, exc_val, exc_tb):关闭类之前做的操作
1.1.3 具体做事情的函数,名字随便起
2.直接见代码:
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
class OPEN(): def __enter__(self): print("in") return self def __exit__(self, exc_type, exc_val, exc_tb): print("out") def do_something(self): print("做一些事情") with OPEN() as f: f.do_something()
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