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List:       pykde
Subject:    Re: [PyQt] Are QThreads compatible with python's threading.RLock?
From:       Phil Thompson <phil () riverbankcomputing ! com>
Date:       2008-07-27 13:22:52
Message-ID: f5deab01bc999acb9f9d65994520d5ef () localhost
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On Sun, 27 Jul 2008 08:55:02 -0400, Darren Dale <dsdale24@gmail.com> wrote:
> On Saturday 26 July 2008 03:48:53 you wrote:
>> On Fri, 25 Jul 2008 17:41:22 -0400, Darren Dale <dsdale24@gmail.com>
> wrote:
>> > I use a library that provides rudimentary thread safety of its objects
>>
>> and
>>
>> > file
>> > I/O using threading.RLock from the python standard library. Could
> anyone
>> > tell
>> > me if PyQt4's QThreads are compatible with these recursive locks?
>>
>> Other than the fact that they will both be implemented using the same OS
>> primitives, Python's and Qt's threading know nothing about each other.
> 
> Thanks Phil. The author of this other library I use added a mechanism to 
> accommodate alternative threading libraries: users can provide their own
> lock 
> object, provided it is reentrant and respect python's context manager 
> protocol. So I think I can can do this:
> 
> class MyRLock(QtCore.QMutex):
> 
>     def __init__(self):
>         super(MyRLock, self).__init__(QtCore.QMutex.Recursive)
> 
>     def __enter__(self):
>         return self.lock()
> 
>     def __exit__(self, type, value, traceback):
>         self.unlock()
> 
>     def acquire(self):
>         return self.lock()
> 
>     def release(self):
>         self.unlock()
> 
> h5.config.RLock = MyRLock
> 
> One last question, concerning context managers: I think the current PyQt4
> way 
> is:
> 
>     def foo(self):
>         with QMutexLocker(self.mutex):
>             [...]
> 
> but if QMutex and friends had __enter__ and __exit__ methods, like
> MyRLock, we 
> could do:
> 
>     def foo(self):
>         with self.mutex:
>             [...]
> 
> Is there a reason (performance?) for using Qt's QMutexLocker to provide
> the 
> context manager, rather than the QMutex itself?

Probably just to keep the Python behaviour in line with the C++ behaviour.

Phil

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