Context-aware return

[Mark Lawrence]

On 10/09/2015 18:54, Steven D'Aprano wrote:
> I have a function which is intended for use at the interactive interpreter,
> but may sometimes be used non-interactively. I wish to change it's output
> depending on the context of how it is being called.
>
> If the function is being called as if it were a procedure or command, that
> is the return result is just ignored, I want to return one thing. But if it
> is being called where the return result goes somewhere, I want to return
> something else. Most importantly, I don't want to pass a flag to the
> function myself, I want the function to know its own context.
>
> I don't mind if it is CPython only, or if it is a bit expensive.
>
> E.g.
>
> def func():
>      do_stuff()
>      if procedure:  # FIXME what goes here???
>          return "Awesome"
>      else:
>          return 999
>
> Now I can do this:
>
> x = func()
> assert x == 999
>
> L = [1, 2, func(), 4]
> assert L[2] == 999
>
> func()
> # interactive interpreter prints "Awesome"
>
> Is such a thing possible, and if so, how would I do it?
>
> If I did this thing, would people follow me down the street booing and
> jeering and throwing things at me?
>

Not unless you were thrown in the Australian equivalent of Broadmoor 
first.  For those who don't know, Broadmoor is a famous place in the UK 
for the criminally insane.

-- 
My fellow Pythonistas, ask not what our language can do for you, ask
what you can do for our language.

Mark Lawrence