[Python-ideas] Make the @contextmanager of contextlib to be a real contextmanager

[Serhiy Storchaka]

05.01.19 14:52, Moon丶sun пише:
> As we know,when we import the module--'contextlib',we can use the 
> decorator '@contextmanager' and keyword ‘yield’ to make a 'instance' of 
> Class '_GeneratorContextManager' in 'contextlib' module,then we can use 
> it like:
> with 'instance' as 'xx':
>      'code block'
>      pass
> But there is a little bug,when the code block raise a error,the instance 
> cannot run the code which after the keyword 'yield'.

This is not a bug.

Consider the following example:

     @contextmanager
     def cm():
         try:
             yield
         except BaseException as err:
             print('Fail:', err)
             raise
         else:
             print('Success')

     with cm():
         1/0

What result would you expect? Test it with the stdlib implementation and 
with your implementation.