ANN: Stackless Python for Python 2.5

[richard.m.tew at gmail.com]

Stackless Python for Python 2.5 is now available.

What is Stackless Python?
=========================

Stackless Python is an enhanced version of the Python programming
language.  It allows programmers to reap the benefits of thread-based
programming without the performance and complexity problems
associated with conventional threads.  The microthreads and channels
that Stackless adds to Python are cheap and lightweight conveniences
which can if used properly, allow clearer and more readable code and
the ability to dispatch with messy and awkward boilerplate like
callbacks or the new generator coroutines.

Where can I get it?
===================

The source code can be obtained from the SVN repository which can
be found here:

  http://svn.python.org/projects/stackless/branches/release25-maint/

Precompiled Windows binaries can be found here:

  http://www.stackless.com/download

How might I benefit from using Stackless Python?
================================================

The most useful example is the replacement socket module.  This
allows all socket operations to be used in parallel, no longer blocking
the rest of your application, or requiring you to use threads or
libraries like asyncore yourself.  Monkeypatch this library in place of
the one in the standard library and all modules which use the
standard socket module gain the same benefit.

  http://www.stackless.com/wiki/Examples

-->8--[ asynch_fetch.py: example code courtesy of Andrew Dalke ]--8<--

import sys
import stacklesssocket
import stackless

sys.modules["socket"] = stacklesssocket

import urllib
import time

def download(uri):
    t1 = time.time()
    f = urllib.urlopen(uri)
    s = f.read()
    t2 = time.time()
    print "Downloaded", uri, "in", "%.1f" % (t2-t1), "seconds"
    return t2-t1


print " === Serial === "
t1 = time.time()
download("http://www.stackless.com/wiki/Tasklets")
download("http://www.stackless.com/wiki/Channels")
t2 = time.time()
print " --->", t2-t1

print " === Parallel === "
t1 = time.time()
stackless.tasklet(download)("http://www.stackless.com/wiki/Tasklets")
stackless.tasklet(download)("http://www.stackless.com/wiki/Channels")
stackless.run()
t2 = time.time()
print " --->", t2-t1

-->8--------------------------------------------------------------8<--

Here are a couple of runs to show that the *same* code works in both
serial and parallel modes, and that parallel really is faster (hence
I'm not bandwidth limited)

% spython asynch_fetch.py
 === Serial ===
Downloaded http://www.stackless.com/wiki/Tasklets in 2.6 seconds
Downloaded http://www.stackless.com/wiki/Channels in 2.7 seconds
 ---> 5.34717988968
 === Parallel ===
Downloaded http://www.stackless.com/wiki/Channels in 4.0 seconds
Downloaded http://www.stackless.com/wiki/Tasklets in 5.4 seconds
 ---> 5.43875193596

% spython asynch_fetch.py
 === Serial ===
Downloaded http://www.stackless.com/wiki/Tasklets in 2.6 seconds
Downloaded http://www.stackless.com/wiki/Channels in 2.7 seconds
 ---> 5.32963705063
 === Parallel ===
Downloaded http://www.stackless.com/wiki/Channels in 2.2 seconds
Downloaded http://www.stackless.com/wiki/Tasklets in 2.7 seconds
 ---> 2.71087312698