Re: New to threads. How do they work?
In message [EMAIL PROTECTED], Dennis Lee Bieber wrote: On Sat, 22 Jul 2006 17:19:22 +1200, Lawrence D'Oliveiro [EMAIL PROTECTED] declaimed the following in comp.lang.python: Perhaps because with threads, data is shared by default. Whereas with processes, it is private by default, and needs to be explicitly shared if you want that. Or just that the name thread was a late-comer for some of us... The Amiga had tasks at the lowest level (these were what the core OS library managed -- that core handled task switching, memory allocation, and IPC [event flags, message ports]). Processes were scheduled by the executive, but had additional data -- like stdin/stdout and environment variables... all the stuff one could access from a command line. Or, confusing for many... Processes were DOS level, Tasks were OS level. Or for a more up-to-date example, how about the Linux way, where processes and threads are just two points on a spectrum of possibilities, all controlled by options to the clone(2) system call. -- http://mail.python.org/mailman/listinfo/python-list
Re: New to threads. How do they work?
On 2006-07-22, Lawrence D'Oliveiro [EMAIL PROTECTED] wrote: I've never understood the aversion people seem to have to threads. Perhaps because with threads, data is shared by default. Whereas with processes, it is private by default, and needs to be explicitly shared if you want that. Only global data is shared. I guess if you use a lot of global data that's an issue. I tend not to. The problem with processes is that sharing data is hard. -- Grant Edwards grante Yow! Are you mentally here at at Pizza Hut?? visi.com -- http://mail.python.org/mailman/listinfo/python-list
Re: New to threads. How do they work?
Dennis Lee Bieber wrote: On Sat, 22 Jul 2006 17:19:22 +1200, Lawrence D'Oliveiro [EMAIL PROTECTED] declaimed the following in comp.lang.python: Perhaps because with threads, data is shared by default. Whereas with processes, it is private by default, and needs to be explicitly shared if you want that. Or just that the name thread was a late-comer for some of us... The Amiga had tasks at the lowest level (these were what the core OS library managed -- that core handled task switching, memory allocation, and IPC [event flags, message ports]). Processes were scheduled by the executive, but had additional data -- like stdin/stdout and environment variables... all the stuff one could access from a command line. Or, confusing for many... Processes were DOS level, Tasks were OS level. On the Amiga, everything was essentially a thread. There was *no* memory protection whatsoever, which made for a wickedly fast -- and unstable -- OS. Now, before Commordore went the way of the Dodo Bird, there was some discussion about adding memory protection to the OS, but that was a very difficult proposition since most if not all of the OS control structures were just that -- basically c structs, with live memory pointers handed around from application to kernel and back. I think we could've done it eventually, but that ship sank. All because of the idiots there that was upper management. But I digress. -- -- Edmond Dantes, CMC And Now for something Completely Different: http://baskets.giftsantiquescollectables.com http://vacation-packages.YouDeserveItNow.com http://cold-remedy.WomenLite.com http://investments.BankOrLoan.com http://coils.IndustrialMetalz.com http://brackets.Auto1Parts.com http://windmill.industrialtips.com Posted Via Usenet.com Premium Usenet Newsgroup Services -- ** SPEED ** RETENTION ** COMPLETION ** ANONYMITY ** -- http://www.usenet.com -- http://mail.python.org/mailman/listinfo/python-list
Re: New to threads. How do they work?
In message [EMAIL PROTECTED], gel wrote: I am attempting to understand threads to use in a network app which I am writing. It is written, somewhere in the philosophy of *nix programming, that threads are a performance hack, to be avoided wherever possible. Use processes in preference to threads. -- http://mail.python.org/mailman/listinfo/python-list
Re: New to threads. How do they work?
On 2006-07-21, Lawrence D'Oliveiro [EMAIL PROTECTED] wrote: In message [EMAIL PROTECTED], gel wrote: I am attempting to understand threads to use in a network app which I am writing. It is written, somewhere in the philosophy of *nix programming, that threads are a performance hack, to be avoided wherever possible. Use processes in preference to threads. I've never understood the aversion people seem to have to threads. Especially in Python they seem very straightforward to use and easy to understand. I find IPC between processes is much more work to do and difficult to get right. Maybe it's just because threads are what I'm used to, since I've been using them for 20+ years -- most of the platforms for which I write don't have processes. -- Grant Edwards grante Yow! INSIDE, I have the at same personality disorder visi.comas LUCY RICARDO!! -- http://mail.python.org/mailman/listinfo/python-list
Re: New to threads. How do they work?
In message [EMAIL PROTECTED], Grant Edwards wrote: On 2006-07-21, Lawrence D'Oliveiro [EMAIL PROTECTED] wrote: In message [EMAIL PROTECTED], gel wrote: I am attempting to understand threads to use in a network app which I am writing. It is written, somewhere in the philosophy of *nix programming, that threads are a performance hack, to be avoided wherever possible. Use processes in preference to threads. I've never understood the aversion people seem to have to threads. Perhaps because with threads, data is shared by default. Whereas with processes, it is private by default, and needs to be explicitly shared if you want that. -- http://mail.python.org/mailman/listinfo/python-list
Re: New to threads. How do they work?
Dennis Lee Bieber wrote: On 19 Jul 2006 19:08:12 -0700, gel [EMAIL PROTECTED] declaimed the following in comp.lang.python: import thread Step one... Skip the thread module and use threading module instead. def create(): pythoncom.CoInitialize() c = wmi.WMI() while 1 : print watching creation watcher = c.watch_for(notification_type=Creation, wmi_class=Win32_Process, delay_secs=1) I don't know WMI, but is that delay a real sleep operation, or a polling loop? And either could be a problem if they hold the GIL -- preventing anything else from running until they return... thread.start_new_thread(create(),()) thread.start_new_thread(delete(),()) At the very least, I suggest commenting out the COM and WMI calls -- test threads that ONLY print output and do a time.sleep(1). That should be sufficient to see if the threads themselves are being started. -- WulfraedDennis Lee Bieber KD6MOG [EMAIL PROTECTED] [EMAIL PROTECTED] HTTP://wlfraed.home.netcom.com/ (Bestiaria Support Staff: [EMAIL PROTECTED]) HTTP://www.bestiaria.com/ Thanks alot for your help. I had tried using threading with a different setup in the function side but did not get success. I think that I have winner now. Thanks again. What follows is the what I have working so far. And another question why do you prefer to us threading and thread? import wmi import pythoncom import threading def create(): pythoncom.CoInitialize() c = wmi.WMI() while 1 : print watching creation watcher = c.watch_for(notification_type=Creation, wmi_class=Win32_Process, delay_secs=1) print watcher() def delete(): pythoncom.CoInitialize() d = wmi.WMI() while 1 : print watching deletion watcher = d.watch_for(notification_type=Deletion, wmi_class=Win32_Process, delay_secs=1) print watcher() import threading threading.Thread(target=create).start() threading.Thread(target=delete).start() Cheers -- http://mail.python.org/mailman/listinfo/python-list
Re: New to threads. How do they work?
Hi I think the answer to your last question is that the threading module provides a high level interface (i.e. easier to use) to the thread module. The thread module is very low-level. Any threaded python scripts I have written (not expert) have used the threading module which is, in my opinion, a very clean easy to use module. Just takes a bit of hacking with to get used to. Cheers!! Dermot. On 19 Jul 2006 23:53:22 -0700, gel [EMAIL PROTECTED] wrote: Dennis Lee Bieber wrote: On 19 Jul 2006 19:08:12 -0700, gel [EMAIL PROTECTED] declaimed the following in comp.lang.python: import thread Step one... Skip the thread module and use threading module instead. def create(): pythoncom.CoInitialize() c = wmi.WMI() while 1 : print watching creation watcher = c.watch_for(notification_type=Creation, wmi_class=Win32_Process, delay_secs=1) I don't know WMI, but is that delay a real sleep operation, or a polling loop? And either could be a problem if they hold the GIL -- preventing anything else from running until they return... thread.start_new_thread(create(),()) thread.start_new_thread(delete(),()) At the very least, I suggest commenting out the COM and WMI calls -- test threads that ONLY print output and do a time.sleep(1). That should be sufficient to see if the threads themselves are being started. -- WulfraedDennis Lee Bieber KD6MOG [EMAIL PROTECTED] [EMAIL PROTECTED] HTTP://wlfraed.home.netcom.com/ (Bestiaria Support Staff: [EMAIL PROTECTED] ) HTTP://www.bestiaria.com/Thanks alot for your help.I had tried using threading with adifferent setup in the function side but did not get success. I think that I have winner now.Thanks again.What follows is the what I haveworking so far.And another question why do you prefer to us threadingand thread?import wmiimport pythoncomimport threading def create(): pythoncom.CoInitialize() c = wmi.WMI() while 1 : print watching creation watcher = c.watch_for(notification_type=Creation, wmi_class=Win32_Process, delay_secs=1) print watcher()def delete(): pythoncom.CoInitialize() d = wmi.WMI() while 1 : print watching deletion watcher = d.watch_for(notification_type=Deletion,wmi_class=Win32_Process, delay_secs=1) print watcher()import threadingthreading.Thread(target=create).start() threading.Thread(target=delete).start()Cheers--http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
