Mailman 3 November 2000 - Python-Dev

Work in progress - coercion/cmp overhaul
by Neil Schemenauer Nov. 13, 2000

Nov. 13, 2000

I making this available now in the hope that it will generate some dicussion: http://arctrix.com/nas/python/coerce-2.diff The patch is based on Marc-Andre Lemburg's coercion patch for 1.5.1 downloaded from the starship: http://starship.python.net/~lemburg/CoercionProposal.html All credit goes to him. The bugs are probably introduced by me. What the patch does: - Introduces a new type flag "NEWSYTLENUMBER". If this flag is set then the tp_as_number methods are treated … [View More]

2 1

Weak References
by Moshe Zadka Nov. 13, 2000

Nov. 13, 2000

For those of you who do not read c.l.py From: shindich(a)my-deja.com Newsgroups: comp.lang.python Subject: Weak References Date: Sun, 12 Nov 2000 11:07:32 GMT Ever wanted to have weak references in Python? Pre-alpha release of PyWeakReference project is now available on Source Forge (http://sourceforge.net/projects/pyweakreference/) Documentation is coming soon... (some docs are available in the Doc subdirectory of the zip file) Sent via Deja.com http://www.deja.com/ Before you buy. - -- … [View More]

4 3

DNS lookups with timeouts ?
by M.-A. Lemburg Nov. 12, 2000

Nov. 12, 2000

I am looking for a way to do DNS resolution with a timeout on the lookup. The easy way to do these lookups using the socket module often result in processes hanging for several seconds (up to minutes on Windows), so I figured emulating the standard DNS lookup (including the /etc/hosts and /etc/resolv.conf files) would be a good idea. I know of the Demo/dns/, but I'm unsure whether it can be tweaked to allow timeouts. Are there any other such implementations out there ? Thanks, -- Marc-Andre … [View More]

3 4

DNS lookups with timeouts ?
by Martin v. Loewis Nov. 12, 2000

Nov. 12, 2000

> Are there any other such implementations out there ? How about http://dustman.net/andy/python/adns-python? Regards, Martin P.S. Is this really on-topic for python-dev?

2 1

Help wanted...
by M.-A. Lemburg Nov. 11, 2000

Nov. 11, 2000

Hi everybody, I just wanted to inform you that I won't be able to work on the patches needed to fix the bugs assigned to me for the next month. I currently have to finish a huge project with a deadline in mid- December which has high priority (anyone ever write a B2B eCommerce order solution in one month ?) ... I hope Python get's me there in time. Anyway, if any of the bugs currently assigned to me need a fast fix, I'd suggest someone else taking a look at them, since I won't be able to do … [View More]

1 0

Stackless pages
by Gordon McMillan Nov. 11, 2000

Nov. 11, 2000

I have put up 6 pages of information about stackless at http://www.mcmillan-inc.com/stackless.html The first page attempts to give a conceptual overview of stackless. Notice I said "conceptual" - I make no attempt to be technically accurate! Next follow 4 pages of tutorial. Mainly this is a discussion of implementing generators and coroutines through the continuation module. It includes rewrites of 2 samples that Tim used to demonstrate his coroutines-implemented-via- threads madness. … [View More]

11 28

RE: [Python-Dev] uthread strawman
by Bill Tutt Nov. 10, 2000

Nov. 10, 2000

From: Christian Tismer [mailto:tismer@tismer.com] > Bill Tutt wrote: > > > > Guido van Rossum [mailto:guido@python.org] wrote: > > > > Christian Tismer wrote: > > > > > Does anybody know of a useful example where continuations > > > > are really needed? > > > [Bill Tutt] > Bill on [server architecture, async state machine] > > > Indeed, this kind of server architecture is typically done with > > > … [View More]

1 0

RE: [Python-Dev] uthread strawman
by Bill Tutt Nov. 10, 2000

Nov. 10, 2000

Guido van Rossum [mailto:guido@python.org] wrote: > > Christian Tismer wrote: > > > Does anybody know of a useful example where continuations > > > are really needed? > [Bill Tutt] > > Well, I don't know about needed, but let me explain a possible sever > > architecture, and then see what new fangled control structure could help it > > become more manageable. (irrespective if the perf #s of such an architecture > > would actually be worth the … [View More]

2 1

[Python-Help] Driver?????
by Martin von Loewis Nov. 9, 2000

Nov. 9, 2000

> My name is Kelli Collins, and I work for the Data Management Team at > IBM. I am currently working with a customer that is considering > using DB2 as their database software, and has asked me to see if I > can locate a driver for Python and DB2...... can you tell if one > exists?????? Hi Kelli, I believe there is actually more than one way to get a database module for Python and DB2. Please have a look at the DB SIG pages, at http://www.python.org/topics/database/ You'… [View More]

2 1

RE: [Python-Dev] uthread strawman
by Bill Tutt Nov. 9, 2000

Nov. 9, 2000

Christian Tismer wrote: > Does anybody know of a useful example where continuations > are really needed? Well, I don't know about needed, but let me explain a possible sever architecture, and then see what new fangled control structure could help it become more manageable. (irrespective if the perf #s of such an architecture would actually be worth the architecture overhead in current CPython) In a high performance server, any non-CPU intensive operation which blocks the thread you're … [View More]on reduces your scalability potential. A fairly common way of writing multi-threaded servers is to have one client per thread , whether this is either a thread pool, or just a simplistic "Create thread, execute work, end thread" approach. Threads are very expensive, and increases the context switch penalty your server is inflicted with. An alternative which reduces the context switch penalty dramatically is to use a thread safe work item queue, and N threads where N is usually some small multiple of the # of CPUs, and is < than the thread pool # of threads. The solution to avoid these threads from blocking is an asynchronous state machine. You asynchronously start the long-time operation, and on completion of this operation insert the request state back in the thread safe queue. You can further extend this idea to reduce the # of threads that you have so that you have only 1 thread/CPU. Each thread being bound directly to the CPU, and not allowed to run on other CPUs. This tries to prevent the threads from CPU switching and ruining the CPU cache, etc. A work item must be able to be executed on any of these threads. Another extension of this idea is to bundle these work items into separate queues based on the state in the state machine. The reason for doing this is trying to prevent unnecessary CPU cache flushing. The downside of this approach is that asynchronous state machines are a pain to debug, maintain, understand, write, etc... (BTW for the curious, the above architecture does allow you to achieve much higher perf for certain tasks than other ways of handling the code, it's been tested and used extensively in some internal C/C++ code (not mine)) The thought occurs to me that continuations would definitely help in this situation. * You'd have more debugging state * The code is organized around other needs besides boundaries between blocking operations. But it's not clear to me (mostly because I haven't applied a lot of thought about it) if coroutines would suffice here. Thoughts? Bill [View Less]

2 1