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Controlling an external program with Python

Paul Duffin pduffin at hursley.ibm.com
Wed Jun 28 07:12:32 EDT 2000 
Alexandre Ferrieux wrote:
> 
> Paul Duffin wrote:
> > While ptys are not rocket science they are also not particularly portable,
> > Expect handles all of this for you.
> 
> In unix, AFAIK the only nonportable part is the *naming* of the pty
> devices. That kind of decision is fairly trivial to make in
> sh/awk/perl/python/tcl...
> 

I think that you will find that there is a lot more too it than that, there
are all sorts of different ways of controlling / configuring the ptys,
defaults are different ...

> > Windows is also a real problem as it
> > does not have ptys and needs to be approached in a completely
> > different way.
> 
> Yes but Expect for Windows is a totally different distrib too :-(
> 

But the interface is the same.

> Hence the suggestion to consider writing a specific Python module (if
> there isn't already - I've just arrived in town): for unix it just opens
> the proper devices and substitutes the popen2() pipes with the masters;
> for windows more trickery is needed (namely, behaving as a debugger to
> trap IO calls!), but should be doable in win32all, shouldn't it ?
> 

Apparently there is a port of Expect for Python so why not use that
rather than try and reimplement it all over again. If you wanted to
be really nice you could create a library containing a nice abstract 
representation of ttys which hides all of the nastiness and then create
a simple binding to that library.

Expect has over 7 years of development and centuries of testing on many
different platforms, do you really want to reproduce that. If so why,
what exactly is wrong with Expect.
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