[IPython-dev] Prompt manager

Fernando Perez fperez.net at gmail.com
Sat Sep 10 15:42:46 EDT 2011

On Sat, Sep 3, 2011 at 5:53 AM, Thomas Kluyver <takowl at gmail.com> wrote:
> First, for generating prompts over ZMQ, we intended to use the
> user_expressions field of an execution request, but this can't easily access
> things that aren't in the user namespace, e.g. os.getcwd(). We can work
> round that using the __import__("os").getcwd() form, but it feels somewhat
> less than ideal. This can however be resolved at a later stage, because the
> frontends currently generate prompts by themselves - my primary aim with
> this is to simplify the rather convoluted code generating prompts for the
> plain terminal.

I've been thinking a fair bit about this issue, and I think we need to
introduce an extra namespace, let's call it frontend_ns, that
frontends can use to execute their code in, keep variables available
without collisions with the user, etc.  Then, things like prompt
computations and similar could be done there.

Granted, if multiple frontends are connected they'd be sharing this
namespace, but at least it would be isolated from the user one.  I
think this would give us a lot of flexibility for interactions with
the frontends.  The need for an isolated space to manage prompts is
what got me thinking along these lines, but I could imagine frontends
keeping richer state and exposing a highly customized view to the user
in a notebook, with an 'app' view, and then allowing them to further
execute code in their own user_ns that only sees the data the app
wants to expose.



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