Debugging pipe IPC

[Ian Clark]

Jim B. Wilson wrote:
> I have the mother (of all) application(s, written in C++) that 
> occasionally outsources certain tasks to a child Python script.  The 
> mother fork/execs (or equivalent) the child and then begins serving the 
> child's requests.
> 
> The child/client sends requests on its stdout and receives responses on 
> stdin.  The interaction is facilitated by a Pyrex extension which handles 
> the lower-level aspects of the conversation and exposes a few functions 
> and classes to the script.
> 
> This part works peachy keen, but debugging has so far been via 
> print>>stderr-and-scratch-head.
> 
> On a contemplative bike ride one day, I imagined how neat it would be to 
> run interactively.  On returning, I began to experiment with rebinding 
> sys.stdin and sys.stdout to /dev/tty, using the "-i" command-line switch, 
> etc. to see if I could devise a child that prompted me with ">>>" and 
> allowed me to compose/test small snippets on the terminal.  So far, no 
> joy.
> 
> Is this possible?  If so, can someone nudge me toward a solution or 
> better yet a recipe?
> 
> Jim Wilson
> Gainesville, FL

You're looking for the cmd module. 
<http://docs.python.org/lib/module-cmd.html>

Ian Clark