Justin Powell wrote: > Hi, I'm looking for suggestions on how to accomplish something in python. If > this is the wrong list for such things, I appologize and please disregard the > rest.
No, this is totally the right place. > My application needs to allow users to create scripts which will be executed > in a statement-by-statement fashion. Here's a little pseudo-code: > > def someUserProgram(): > while 1: > print "I am a user program" > > def mainProgram(): > someProgram = someUserProgram > while 1: > print "Doing some stuff here" > executeOneStatement(someProgram) > > def executeOneStatement(program): > # What goes in here? > > I would expect the output to look like this: > > Doing some stuff here > Doing some stuff here > I am a sub program > Doing some stuff here > Doing some stuff here > I am a sub program > etc. > > It's possible to use generators to accomplish this, but unfortunately a > state-ment by statement executing would require that every other statement is > a yield. That would either force the users to put in a yield after every > statement, or require a mechanism that parses the source and inserts yield > statement before execution. Neither of these are really satisfactory. Hmm, ok, so you don't want to manually interfere with the partial programs. What I could think of is some form of code manipulation where you scan the source code of the function you get passed and add a yield after each statement. http://docs.python.org/dev/lib/inspect-source.html http://docs.python.org/dev/lib/module-parser.html > The other methods I've considered for doing this cleanly (subclassing the > debugger, or the interactive interpreter) seem to revolve around sys.settrace > and a callback trace function. I couldn't figure out a way to use this > mechanism to resume the main loop from the trace function, and then also > resume the user program the next time around, without the call stack just > spiraling out of control. I assume that tracing would be a good solution, though. Maybe someone else can tell you how to use it better than I could. You should tell us a bit more about the actual use case, i.e. *why* you need this. Maybe there's a better solution to the whole problem after all. Stefan -- http://mail.python.org/mailman/listinfo/python-list
