[Python-Dev] subprocess crossplatformness and async communication

[anatoly techtonik]

Greetings,

This turned out to be a rather long post that in short can be summarized as:
"please-please-please, include asynchronous process communication in
subprocess module and do not allow "available only on ..."
functionality", because it hurts the brain".

Code to speak for itself: http://code.activestate.com/recipes/440554/


The subprocess module was a great step forward to unify various spawn
and system and exec and etc. calls in one module, and more importantly
- in one uniform API. But this API is partly crossplatform, and I
believe I've seen recent commits to docs with more unix-only
differences in this module.

The main point of this module is to "allows you to spawn new
processes, connect to their input/output/error pipes, and obtain their
return codes". PEP 324 goal is also to make "make Python an even
better replacement language for over-complicated shell scripts".

Citing pre-subrocess PEP 324, "Currently, Python has a large number of
different functions for process creation. This makes it hard for
developers to choose." Now there is one class with many methods and
many platform-specific comments and notices. To make thing worse
people on Unix use subprocess with fcntl and people on windows tend
not to use it at all, because it looks complicated and doesn't solve
the problem with asynchronous communication.

That I suggest is to add either support for async crossplatfrom
read/write/probing of executed process or a comment at the top of
module documentation that will warn that subprocess works in blocking
mode. With async mode you can emulate blocking, the opposite is not
possible. This will save python users a lot of time.

Thanks for reading my rant.


BTW, the proposed change is top 10 python recipe on ActiveState
http://code.activestate.com/recipes/langs/python/

-- 
--anatoly t.