Threads

[placid]

Hi all,

In Python, Threads cannot be paused, i remember reading this somewhere,
so is there a way around this ?

TIA

[Carl J. Van Arsdall]

Re: Threads

placid wrote:[color=blue]
> Hi all,
>
> In Python, Threads cannot be paused, i remember reading this somewhere,
> so is there a way around this ?
>[/color]

When you say paused do you mean paused by an external source or paused
by a call internal to the thread? There are plenty of synchronization
constructs for making threads wait: Check out Events and Conditions

-carl



--

Carl J. Van Arsdall
cvanarsdall@mvi sta.com
Build and Release
MontaVista Software

[placid]

Re: Threads


Carl J. Van Arsdall wrote:[color=blue]
> placid wrote:[color=green]
> > Hi all,
> >
> > In Python, Threads cannot be paused, i remember reading this somewhere,
> > so is there a way around this ?
> >[/color]
>
> When you say paused do you mean paused by an external source or paused
> by a call internal to the thread? There are plenty of synchronization
> constructs for making threads wait: Check out Events and Conditions[/color]

I have a thread that has a job Queue, it continuosly polls this queue
to see if there are any jobs for it, what i really wont to be able to
do is, when the queue is empty, i want the thread to pause (or more
technical, i want the thread to block) until the queue gets populated
again. Is this possible ?

[color=blue]
>
> -carl
>
>
>
> --
>
> Carl J. Van Arsdall
> cvanarsdall@mvi sta.com
> Build and Release
> MontaVista Software[/color]

[David Reed]

Re: Threads


On May 11, 2006, at 8:02 PM, placid wrote:
[color=blue]
>
> Carl J. Van Arsdall wrote:[color=green]
>> placid wrote:[color=darkred]
>>> Hi all,
>>>
>>> In Python, Threads cannot be paused, i remember reading this
>>> somewhere,
>>> so is there a way around this ?
>>>[/color]
>>
>> When you say paused do you mean paused by an external source or
>> paused
>> by a call internal to the thread? There are plenty of
>> synchronization
>> constructs for making threads wait: Check out Events and Conditions[/color]
>
> I have a thread that has a job Queue, it continuosly polls this queue
> to see if there are any jobs for it, what i really wont to be able to
> do is, when the queue is empty, i want the thread to pause (or more
> technical, i want the thread to block) until the queue gets populated
> again. Is this possible ?
>
>[/color]


The previous poster answered your question - you want to use a
condition variable.

http://docs.python.org/lib/condition-objects.html

Dave

[placid]

Re: Threads


David Reed wrote:[color=blue]
> On May 11, 2006, at 8:02 PM, placid wrote:
>[color=green]
> >
> > Carl J. Van Arsdall wrote:[color=darkred]
> >> placid wrote:
> >>> Hi all,
> >>>
> >>> In Python, Threads cannot be paused, i remember reading this
> >>> somewhere,
> >>> so is there a way around this ?
> >>>
> >>
> >> When you say paused do you mean paused by an external source or
> >> paused
> >> by a call internal to the thread? There are plenty of
> >> synchronization
> >> constructs for making threads wait: Check out Events and Conditions[/color]
> >
> > I have a thread that has a job Queue, it continuosly polls this queue
> > to see if there are any jobs for it, what i really wont to be able to
> > do is, when the queue is empty, i want the thread to pause (or more
> > technical, i want the thread to block) until the queue gets populated
> > again. Is this possible ?
> >
> >[/color]
>
>
> The previous poster answered your question - you want to use a
> condition variable.
>
> http://docs.python.org/lib/condition-objects.html[/color]

thanks, this is what i was after
[color=blue]
>
> Dave[/color]

[Peter Otten]

Re: Threads

placid wrote:
[color=blue]
> I have a thread that has a job Queue, it continuosly polls this queue
> to see if there are any jobs for it, what i really wont to be able to
> do is, when the queue is empty, i want the thread to pause (or more
> technical, i want the thread to block) until the queue gets populated
> again. Is this possible ?[/color]

Isn't that the default behaviour of Queue.get()?

Peter

[Alex Martelli]

Re: Threads

Peter Otten <__peter__@web. de> wrote:
[color=blue]
> placid wrote:
>[color=green]
> > I have a thread that has a job Queue, it continuosly polls this queue
> > to see if there are any jobs for it, what i really wont to be able to
> > do is, when the queue is empty, i want the thread to pause (or more
> > technical, i want the thread to block) until the queue gets populated
> > again. Is this possible ?[/color]
>
> Isn't that the default behaviour of Queue.get()?[/color]

Absolutely! placid, just call the get method of that Queue instance: if
the queue is empty your thread DOES pause, or block, until there's some
item put on the queue by another thread.


Alex

[Edward Elliott]

Re: Threads

Dennis Lee Bieber wrote:
[color=blue]
> On 11 May 2006 17:02:51 -0700, "placid" <Bulkan@gmail.c om> declaimed the
> following in comp.lang.pytho n:[color=green]
>> do is, when the queue is empty, i want the thread to pause (or more
>> technical, i want the thread to block) until the queue gets populated
>> again. Is this possible ?
>>[/color]
> Did you read the documentation for Queue methods?
>
> x = q.get(true) #blocks until data is available[/color]

Like a good lawyer, Dennis knows the answer before he asks the question.

--
Edward Elliott
UC Berkeley School of Law (Boalt Hall)
complangpython at eddeye dot net

[placid]

Re: Threads


Dennis Lee Bieber wrote:[color=blue]
> On 11 May 2006 17:02:51 -0700, "placid" <Bulkan@gmail.c om> declaimed the
> following in comp.lang.pytho n:
>
>[color=green]
> > I have a thread that has a job Queue, it continuosly polls this queue
> > to see if there are any jobs for it, what i really wont to be able to
> > do is, when the queue is empty, i want the thread to pause (or more
> > technical, i want the thread to block) until the queue gets populated
> > again. Is this possible ?
> >[/color]
> Did you read the documentation for Queue methods?[/color]

there is no need to be patronizing about this dude, im just learning
Python in my spare time, as im a Intern Software Engineer
[color=blue]
>
> x = q.get(true) #blocks until data is available[/color]


this is even better, thanks dude
[color=blue]
> --
> Wulfraed Dennis Lee Bieber KD6MOG
> wlfraed@ix.netc om.com wulfraed@bestia ria.com
> HTTP://wlfraed.home.netcom.com/
> (Bestiaria Support Staff: web-asst@bestiaria. com)
> HTTP://www.bestiaria.com/[/color]

[Sybren Stuvel]

Re: Threads

placid enlightened us with:[color=blue][color=green]
>> Did you read the documentation for Queue methods?[/color]
>
> there is no need to be patronizing about this dude, im just learning
> Python in my spare time, as im a Intern Software Engineer[/color]

There is nothing patronizing about the question, it's merely an
enquiry to a possible fact. If you're going to be a techie, you should
learn stuff like that.

Sybren
--
The problem with the world is stupidity. Not saying there should be a
capital punishment for stupidity, but why don't we just take the
safety labels off of everything and let the problem solve itself?
Frank Zappa

[placid]

Re: Threads


Sybren Stuvel wrote:[color=blue]
> placid enlightened us with:[color=green][color=darkred]
> >> Did you read the documentation for Queue methods?[/color]
> >
> > there is no need to be patronizing about this dude, im just learning
> > Python in my spare time, as im a Intern Software Engineer[/color]
>
> There is nothing patronizing about the question, it's merely an
> enquiry to a possible fact. If you're going to be a techie, you should[/color]

true enough
[color=blue]
> learn stuff like that.[/color]

its always said that (in programming) that the easiest solution to a
problem is hard to find, well for me posting my question here was the
hardest, when the easier solution was for me to go look at the Python
documentation!
[color=blue]
>
> Sybren
> --
> The problem with the world is stupidity. Not saying there should be a
> capital punishment for stupidity, but why don't we just take the
> safety labels off of everything and let the problem solve itself?
> Frank Zappa[/color]

[Sybren Stuvel]

Re: Threads

placid enlightened us with:[color=blue]
> its always said that (in programming) that the easiest solution to a
> problem is hard to find[/color]

Yeah, that's true allright!

Sybren
--
The problem with the world is stupidity. Not saying there should be a
capital punishment for stupidity, but why don't we just take the
safety labels off of everything and let the problem solve itself?
Frank Zappa

[antred]

Re: Threads

Aww shoot, I never knew that!! LOL, I implemented my own worker thread
class using a mutex protected job list and a pair of connected sockets
for interprocess communication when I could just have used the darn
Queue module instead. Grrrrr .... hehe.

[Grant Edwards]

Re: Threads

On 2006-05-12, antred <NutJob@gmx.net > wrote:

Nerver knew what? Please quote for context.
[color=blue]
> Aww shoot, I never knew that!![/color]

http://docs.python.org/lib/QueueObjects.html

get([block[, timeout]])

Remove and return an item from the queue. If optional args
block is true and timeout is None (the default), block if
necessary until an item is available. [...]

--
Grant Edwards grante Yow! VICARIOUSLY
at experience some reason
visi.com to LIVE!!

[Grant Edwards]

Re: Threads

On 2006-05-12, Sybren Stuvel <sybrenUSE@YOUR thirdtower.com. imagination> wrote:[color=blue]
> placid enlightened us with:[color=green][color=darkred]
>>> Did you read the documentation for Queue methods?[/color]
>>
>> there is no need to be patronizing about this dude, im just learning
>> Python in my spare time, as im a Intern Software Engineer[/color]
>
> There is nothing patronizing about the question, it's merely
> an enquiry to a possible fact. If you're going to be a techie,
> you should learn stuff like that.[/color]

It's also valuable information to the maintainers of the
documentation. If he _did_ read the documentation and still
didn't know that Queue.get() could block, then one might ask
how the documentation could be improved.

--
Grant Edwards grante Yow! Is this ANYWHERE,
at USA?
visi.com