with上下文管理协议以及contextlib

#try except finally
def exe_try():
    try:
        print ("code started")
        raise KeyError
        return 1
    except KeyError as e:
        print ("key error")
        return 2
    else:
        print ("other error")
        return 3
    finally:
        print ("finally")
        # return 4

#上下文管理器协议
class Sample:
    def __enter__(self):
        print ("enter")
        #获取资源
        return self
    def __exit__(self, exc_type, exc_val, exc_tb):
        #释放资源
        print ("exit")
    def do_something(self):
        print ("doing something")

with Sample() as sample:
    sample.do_something()

# if __name__ == "__main__":
#     result = exe_try()
#     print (result)

 

import contextlib

@contextlib.contextmanager
def file_open(file_name):
    print ("file open")
    yield {}
    print ("file end")

with file_open("bobby.txt") as f_opened:
    print ("file processing")