[Patches] [ python-Patches-1175933 ] threading.Condition.wait() return value indicates timeout

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Patches item #1175933, was opened at 2005-04-04 04:09
Message generated for change (Comment added) made by mdehoon
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https://sourceforge.net/tracker/?func=detail&atid=305470&aid=1175933&group_id=5470

Category: Library (Lib)
Group: Python 2.4
Status: Open
Resolution: None
Priority: 5
Submitted By: Martin Blais (blais)
Assigned to: Nobody/Anonymous (nobody)
Summary: threading.Condition.wait() return value indicates timeout

Initial Comment:
A condition variable returns in two cases: it was
notified by another thread, or it timed out (if a
timeout was specified).  See an example in the popular
Boost C++ library:

http://boost.org/doc/html/condition.html

This patch adds this capability to the Python
threading.Condition.wait() method, which used to return
nothing.  I added the relevant couple of lines to the
documentaion as well (see patch).

(An example is using a condition variable as a sentinel
for exiting a loop or a polling thread.  Using the
return value one can decide whether to exit the loop or
not.)


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Comment By: Michiel de Hoon (mdehoon)
Date: 2005-04-29 15:59

Message:
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user_id=488897

This looks like a good idea to me. It will help to clean up
the "get" method in Queue.py, which now has:

                while self._empty():
                    remaining = endtime - _time()
                    if remaining <= 0.0:
                        raise Empty
                    self.not_empty.wait(remaining)

Here, self.not_empty is an object of the class
threading.Condition. It seems odd that first we wait for
self.not_empty.wait to return, and then have to check
self._empty(), even though self.not_empty.wait could have
told us directly if it was notified or it timed out.

I'll write a message to python-dev in support of this patch
(I'm a mere patch reviewer, not an official Python developer).

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https://sourceforge.net/tracker/?func=detail&atid=305470&aid=1175933&group_id=5470