[Python-Dev] Re: Activating `-i' from inside a script?

[Guido van Rossum]

> On c.l.py someone asked about forcing a tailend interactive shell from
> within the program.  Try Melhase proposed:
> 
>     import os
> 
>     if __name__ == '__main__':
>         discrepancy = True
>         if discrepancy:
>             os.environ['PYTHONINSPECT'] = "why yes, i'd like that"
> 
> but observed that it doesn't work because the environment variable is only
> checked at program start.
> 
> This change to Modules/main.c makes the above work:
> 
> % cvs diff main.c
> Index: main.c
> ===================================================================
> RCS file: /cvsroot/python/python/dist/src/Modules/main.c,v
> retrieving revision 1.77
> diff -c -r1.77 main.c
> *** main.c      30 Mar 2003 17:09:58 -0000      1.77
> --- main.c      27 Jun 2003 11:50:42 -0000
> ***************
> *** 418,423 ****
> --- 418,428 ----
>                         filename != NULL, &cf) != 0;
>         }
>   
> +       /* also check at the end in case the program set PYTHONINSPECT */
> +       if (!saw_inspect_flag &&
> +           (p = Py_GETENV("PYTHONINSPECT")) && *p != '\0')
> +               inspect = 1;
> + 
>         if (inspect && stdin_is_interactive &&
>             (filename != NULL || command != NULL))
>                 /* XXX */
> 
> I can't see that it would affect the functioning of any programs other than
> those which set PYTHONINSPECT now.  (But why would they do that and what's
> the likelihood such programs exist?)
> 
> Any chance this could be squeezed in?  It seems rather elegant:
> 
>     try:
>         something which fails
>     except:
>         os.environ["PYTHONINSPECT"] = 1
>         raise
> 
> (I know we're at beta1, and the programmer could re-run with -i.  But
> still...)

Looks harmless to me.  Thomas Heller's alternative really does
something different.  Skip can check it in.

--Guido van Rossum (home page: http://www.python.org/~guido/)