How to control a console based program from Python

[Will Stuyvesant]

I never used the popen or popen2 libraries but it is my understanding
that they can capture the output of console based programs. Is it
also possible to send keystrokes to console base programs?

I would like to program a Python program that can play for instance
the tty version of nethack 3.4.3 on Windows, simulating a human
player: for nethack it would not be possible to know if a human or a
computer program is playing it. It is a console based program, it
accepts keystrokes and outputs characters on the (Windows) console
box. I did see that WConio can read characters from the screen,
perhaps I can use that, have to experiment with it some more. But how
to send keystrokes? Any help and ideas are much appreciated. And a
happy new year of course!

[Samuel Walters]

Re: How to control a console based program from Python

|Thus Spake Will Stuyvesant On the now historical date of Sat, 03 Jan 2004
02:24:32 -0800|
[color=blue]
> I never used the popen or popen2 libraries but it is my understanding
> that they can capture the output of console based programs. Is it also
> possible to send keystrokes to console base programs?
>
> I would like to program a Python program that can play for instance the
> tty version of nethack 3.4.3 on Windows, simulating a human player: for
> nethack it would not be possible to know if a human or a computer
> program is playing it. It is a console based program, it accepts
> keystrokes and outputs characters on the (Windows) console box. I did
> see that WConio can read characters from the screen, perhaps I can use
> that, have to experiment with it some more. But how to send keystrokes?
> Any help and ideas are much appreciated. And a happy new year of
> course![/color]

The fact that you're on a microsoft box makes the issue of console-based
programs significantly more sticky than it would be on a *nix system.

You may know this already, but in case you don't, here's a bit of
technical info to get you oriented.

Unix was, early on, designed around the idea of pipes. Pretty much every
program reads from stdin and writes to stdout. Thus, there's a constant
flow of data into the program and a constant flow out. On *nix systems, a
terminal pushes your keystrokes to stdin, and interprets the results it
gets from stdout. (This description is oversimplified, but it will do.)
The results contain certain codes that, depending on the terminal, move
the cursor around, change colors and such. A good resource on all this
is: http://www.faqs.org/docs/artu/index.html

Even if you're not that interested in unix stuff, it's a good read because
Python inherits a lot of the unix philosophy.

MS-DOS, and hence microsoft console programs, were based on an entirely
different philosophy, that of CP/M. Whereas Unix was designed for big
computers with many users running many programs at once, CP/M was designed
for computers with one user running only one program. CP/M simply
abstracted the low-level hardware calls through the use of interrupts.
Interrupts are called interrupts because they do exactly that: they
interrupt the entire computer, run some low-level code, then return
control to the (one and only) program running. I don't think pipes were
ever part of CP/M, but at some point they were grafted onto MS-DOS. (This
was probably to make some grumpy unix wizards complain less vocally about
having to write code for single user machines.) Almost nothing useful is
done with pipes in MS-DOS. When you run a console program in Windows,
it's a special program that pretends to be the old Dos system. Apropos
Docs:

http://www.wkonline.com/d/CPM.html

http://www.wkonline.com/d/MS-DOS.html

Chances are that the nethack you're running displays to the screen via
these crufty old Dos interrupts. While it is possible to "steal" these
interrupts (and snag their data) I don't know of any libraries that would
let you do that, I wouldn't try it unless you've got some serious sorcery
in you. To give you an idea of how complex it is, somewhere around here,
I've got a manual on all those interrupts and I think it's about 6 inches
thick and involves manipulating the processor registers directly. You can
probably find some c code to do that, but umm... I dunno. I always just
inlined assembly when I was working with MS-Dos.
(;Please, god no ABEND NOW!
MOV AH,4Ch
MOV AL,01h
INT 21h ;*weeps* Fifteen years later, and I still remember that.
)

http://users.win.be/W0005997/GI/dosref.html

If you *really* want to try making a robot that plays nethack, I suggest
installing cygwin, which gives you a unix environment on top of your
windows system, then compiling nethack for it and *then* you'll have
access to proper pipes. Besides, you'll get to dabble a bit in *nix land.
You might like it.

http://www.cygwin.com/

Sam Walters

p.s. You might try taking this to the python-tutor list. You will
probably get more answers to questions like this.

--
Never forget the halloween documents.

http://www.opensource.org/halloween/

""" Where will Microsoft try to drag you today?
Do you really want to go there?"""