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]

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

-carl



--

Carl J. Van Arsdall
(e-mail address removed)
Build and Release
MontaVista Software

 

[placid]

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

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 ?

 

[David Reed]

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 ?

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

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

Dave

 

[placid]

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

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

thanks, this is what i was after

 

[Peter Otten]

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 ?

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

Peter

 

[Alex Martelli]

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

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

 

[Dennis Lee Bieber]

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 ?

Did you read the documentation for Queue methods?

x = q.get(true) #blocks until data is available
--
Wulfraed Dennis Lee Bieber KD6MOG
(e-mail address removed) (e-mail address removed)
HTTP://wlfraed.home.netcom.com/
(Bestiaria Support Staff: (e-mail address removed))
HTTP://www.bestiaria.com/

 

[Edward Elliott]

Did you read the documentation for Queue methods?

x = q.get(true) #blocks until data is available

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

 

[placid]

Did you read the documentation for Queue methods?

there is no need to be patronizing about this dude, im just learning
Python in my spare time, as im a Intern Software Engineer

x = q.get(true) #blocks until data is available

this is even better, thanks dude

 

[Sybren Stuvel]

placid enlightened us with:

there is no need to be patronizing about this dude, im just learning
Python in my spare time, as im a Intern Software Engineer

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

 

[placid]

placid enlightened us with:

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

true enough

learn stuff like that.

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!

 

[Sybren Stuvel]

placid enlightened us with:

its always said that (in programming) that the easiest solution to a
problem is hard to find

Yeah, that's true allright!

Sybren

 

[antred]

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]

Nerver knew what? Please quote for context.

Aww shoot, I never knew that!!

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]

placid enlightened us with:

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.

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.

 

[Dennis Lee Bieber]

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.

If it means anything -- I typically do bring up the help files and
cut&paste the relevant paragraph. But I had a 24-hour backlog and it was
late at night so a straight off-the-cuff entry was made. Though I
suppose one could go back to the "smart questions" FAQ, and have
suggested the original poster tell us what documentation was read in
search of a solution prior to their post (in which case my short
response could be interpreted as a less than subtle hint to read the
references first).
--
Wulfraed Dennis Lee Bieber KD6MOG
(e-mail address removed) (e-mail address removed)
HTTP://wlfraed.home.netcom.com/
(Bestiaria Support Staff: (e-mail address removed))
HTTP://www.bestiaria.com/

 

[placid]

If it means anything -- I typically do bring up the help files and
cut&paste the relevant paragraph. But I had a 24-hour backlog and it was
late at night so a straight off-the-cuff entry was made. Though I
suppose one could go back to the "smart questions" FAQ, and have
suggested the original poster tell us what documentation was read in
search of a solution prior to their post (in which case my short
response could be interpreted as a less than subtle hint to read the
references first).

telling me to read the documentation would have been a good reminder
dude!

--
Wulfraed Dennis Lee Bieber KD6MOG
(e-mail address removed) (e-mail address removed)
HTTP://wlfraed.home.netcom.com/
(Bestiaria Support Staff: (e-mail address removed))
HTTP://www.bestiaria.com/

thanks again for all of you who replied with great answers.