sys.ps1 is not defined

[Roald de Vries]

I found out from the python mailing list that to according to the Python specification, to be a valid Python shell, iPython has to implement sys.ps1 and sys.ps2.

[Fernando Perez (fdo.perez)]

And what problem does this cause in *actual practice*? IPython provides its own prompt mechanism, so it does not rely on the sys.ps{1,2} variables.

If you can post an actual problem caused by this please reopen.

[Roald de Vries (ipython)]

Clearly, becauses sys.ps{1,2} is part of the python definition, not every valid python program runs well on ipython. But, I admit, not many will have problems with this in practice.

A practical problem is this: I have a script that I want to use in 2 ways:
- for running from bash with command line arguments (subcommands); it executes the subcommands and exits
- for starting an interactive session in ipython

The script should check whether it is interactive or not, an in case it is, it should make available some functions and 'aliases'. The best (only?) way to find this out (for non-ipython-python) seems to be whether sys.ps{1,2} is defined or not.

I think it would be elegant if the ipython prompt mechanism could be made consistent with the sys.ps{1,2} mechanism.

[Fernando Perez (fdo.perez)]

On Sun, May 23, 2010 at 5:38 AM, Roald de Vries <email address hidden> wrote:
> Clearly, becauses sys.ps{1,2} is part of the python definition, not
> every valid python program runs well on ipython. But, I admit, not many
> will have problems with this in practice.
>
> A practical problem is this: I have a script that I want to use in 2 ways:
> - for running from bash with command line arguments (subcommands); it executes the subcommands and exits
> - for starting an interactive session in ipython
>
> The script should check whether it is interactive or not, an in case it
> is, it should make available some functions and 'aliases'. The best
> (only?) way to find this out (for non-ipython-python) seems to be
> whether sys.ps{1,2} is defined or not.
>
> I think it would be elegant if the ipython prompt mechanism could be
> made consistent with the sys.ps{1,2} mechanism.
>

We've moved IPython development to github, so I've opened this as a
bug in the new tracker:

http://github.com/ipython/ipython/issues/issue/123

And with your new comments I agree with you, plus it's an easy fix.

Thanks for the report!

Cheers,

f