On Wed, Jan 21, 2009 at 02:45, Guillaume Chereau <charlie137@gmail.com> wrote:

Just realized i clicked "reply" instead of 'reply to all"

---------- Forwarded message ---------- From: Guillaume Chereau <charlie137@gmail.com> Date: Wed, Jan 21, 2009 at 12:00 PM Subject: Re: [Python-ideas] standard library proposal for "tasklets" using generators To: Guido van Rossum <guido@python.org>

Thanks for the answer,

I understand the concern here.

I still think having such a library, if not as a standard python lib, but at least as an independent one, that could then be used by all the project using such pattern (twisted, kiwi, gobject, etc.) would be a good idea. I will try to contact those different projects for suggestions.

If the package really takes off and it turns out there is a good design that leads to clean code this can be re-evaluated. But getting a third-party library out there that has wide usage is a good first step. -Brett

I also have to say one of my secret hope was that the pypy interpreter could eventually understand this kind of 'tasklet' generators and generate C or other language code out of it, since pypy already has support for tasklets, but using a syntax that can't be interpreted by cpython.

- Guillaume

On Wed, Jan 21, 2009 at 10:56 AM, Guido van Rossum <guido@python.org> wrote:

...

The pattern of invoking all sorts of stuff that may wait indefinitely using yield has been proposed before, but I find it creates rather awkward code compared to using plain threads. Not something I'd like to encourage by having standard decorators and other APIs around this idea. I believe Twisted has something like this, and that's probably a good place to isolate such patterns; in their case they really want/need this, so they put up with the awkwardness. Putting the necessary decorators/APIs in the language doesn't do much about the awkwardness, so I don't think we should do this.

On Tue, Jan 20, 2009 at 6:36 PM, Guillaume Chereau <charlie137@gmail.com> wrote:

...

Hello, Thanks to the introduction of new generator features, as described in PEP 0342, it is possible to write what I would call "tasklet" (I am no sure what should be the term exactly). tasklet are a way to write callback based code that looks like thread. Example :

(assuming we have a function sleep(sec, callback) that will call the callback after `sec` seconds)

@tasklet task1(): print "sleep" yield Wait(sleep, 5) print "called after sleep" yield 10 # returned value

@tasklet task2(): for i in range(10): value = yield task1()

(the same thing using callback only would be quite difficult to read)

The library should provide -the names are not very important- a Tasklet class, plus a tasklet decorator to turn any generator into a tasklet, plus a Wait function to turn a callback function into a tasklet, plus maybe a few other functions.

In many cases this kind of library would be very useful. I am currently using something very similar for a project I am working on [0]. the kiwi project also have a similar library [1] (but the syntax is not really nice because they don't take advantage of the PEP 0342 features.)

I guess more and more people may try to use similar library in the future, but the problem is that the implementation of it is really not trivial, so I would like to suggest having such a library in the standard set of python libraries.

Do you think this is a good idea ?

cheers,

Guillaume

[0] http://git.openmoko.org/?p=tichy.git;a=blob;f=tichy/tasklet.py [1] http://www.async.com.br/projects/kiwi/api/kiwi.tasklet.html

-- http://charlie137.blogspot.com/ _______________________________________________ Python-ideas mailing list Python-ideas@python.org http://mail.python.org/mailman/listinfo/python-ideas

-- --Guido van Rossum (home page: http://www.python.org/~guido/)

-- http://charlie137.blogspot.com/

-- http://charlie137.blogspot.com/ _______________________________________________ Python-ideas mailing list Python-ideas@python.org http://mail.python.org/mailman/listinfo/python-ideas

On Wed, Jan 21, 2009 at 02:45, Guillaume Chereau <charlie137@gmail.com> wrote:

Just realized i clicked "reply" instead of 'reply to all"

---------- Forwarded message ---------- From: Guillaume Chereau <charlie137@gmail.com> Date: Wed, Jan 21, 2009 at 12:00 PM Subject: Re: [Python-ideas] standard library proposal for "tasklets" using generators To: Guido van Rossum <guido@python.org>

Thanks for the answer,

I understand the concern here.

I still think having such a library, if not as a standard python lib, but at least as an independent one, that could then be used by all the project using such pattern (twisted, kiwi, gobject, etc.) would be a good idea. I will try to contact those different projects for suggestions.

If the package really takes off and it turns out there is a good design that leads to clean code this can be re-evaluated. But getting a third-party library out there that has wide usage is a good first step. -Brett

I also have to say one of my secret hope was that the pypy interpreter could eventually understand this kind of 'tasklet' generators and generate C or other language code out of it, since pypy already has support for tasklets, but using a syntax that can't be interpreted by cpython.

- Guillaume

On Wed, Jan 21, 2009 at 10:56 AM, Guido van Rossum <guido@python.org> wrote:

...

The pattern of invoking all sorts of stuff that may wait indefinitely using yield has been proposed before, but I find it creates rather awkward code compared to using plain threads. Not something I'd like to encourage by having standard decorators and other APIs around this idea. I believe Twisted has something like this, and that's probably a good place to isolate such patterns; in their case they really want/need this, so they put up with the awkwardness. Putting the necessary decorators/APIs in the language doesn't do much about the awkwardness, so I don't think we should do this.

On Tue, Jan 20, 2009 at 6:36 PM, Guillaume Chereau <charlie137@gmail.com> wrote:

...

Hello, Thanks to the introduction of new generator features, as described in PEP 0342, it is possible to write what I would call "tasklet" (I am no sure what should be the term exactly). tasklet are a way to write callback based code that looks like thread. Example :

(assuming we have a function sleep(sec, callback) that will call the callback after `sec` seconds)

@tasklet task1(): print "sleep" yield Wait(sleep, 5) print "called after sleep" yield 10 # returned value

@tasklet task2(): for i in range(10): value = yield task1()

(the same thing using callback only would be quite difficult to read)

The library should provide -the names are not very important- a Tasklet class, plus a tasklet decorator to turn any generator into a tasklet, plus a Wait function to turn a callback function into a tasklet, plus maybe a few other functions.

In many cases this kind of library would be very useful. I am currently using something very similar for a project I am working on [0]. the kiwi project also have a similar library [1] (but the syntax is not really nice because they don't take advantage of the PEP 0342 features.)

I guess more and more people may try to use similar library in the future, but the problem is that the implementation of it is really not trivial, so I would like to suggest having such a library in the standard set of python libraries.

Do you think this is a good idea ?

cheers,

Guillaume

[0] http://git.openmoko.org/?p=tichy.git;a=blob;f=tichy/tasklet.py [1] http://www.async.com.br/projects/kiwi/api/kiwi.tasklet.html

-- http://charlie137.blogspot.com/ _______________________________________________ Python-ideas mailing list Python-ideas@python.org http://mail.python.org/mailman/listinfo/python-ideas

-- --Guido van Rossum (home page: http://www.python.org/~guido/)

-- http://charlie137.blogspot.com/

-- http://charlie137.blogspot.com/ _______________________________________________ Python-ideas mailing list Python-ideas@python.org http://mail.python.org/mailman/listinfo/python-ideas