Repeating Thread Error

[Marc 'BlackJack' Rintsch]

On Fri, 06 Jul 2007 14:40:16 -0700, Jonathan Shan wrote:

> I am trying to call a function every 5 seconds. My understanding of
> time.sleep() is during the sleep time everything "stops".

Not "everything", just the thread in which `sleep()` is called.

> However, in my application, there are background processes that must be
> running continuously during the five second interval.

Then start them as threads and they will run all the time.

> Thus, threading.Timer seems like a good function. Here is the relevant
> code:
> 
> # background processes
> t = threading.Timer(5.0, function_name, [arguments])
> while True:
>      # Do background processes run inside while loop?
>      t.start()
> 
> The above code generates an error:
> AssertionError: thread already started
> 
> Any hints on how to fix the error?

A thread can only be started once but you try to start the `Timer` over
and over.  And you don't wait, so even if this would "work" you would
start many, many `Timer`\s as fast as the ``while`` loop runs. The
`Timer`\s would all run the function after five seconds.  It's like::

  while True:
      function_name(*arguments)

just with a five second delay.

> Also, do background processes run inside while loops?

This question doesn't make much sense to me.  Do ``while`` loops block
other threads?  No of course not.

Ciao,
	Marc 'BlackJack' Rintsch