[PyQt] help a noob, Im a noob (David Boddie)

[Brian McDonald]

David, 

Thank you so much. Your suggestion got me thinking the right way and now the program is working just as I want it to. To prove how much of a noob I am, I should tell you, now that it is working I could sit and watch the screen toggle between queries for hours! HA. Feels like a major achievement. Of course, I realize its not really at all, but boy it sure feels cool. 

Thanks, 

Brian 

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Sent: Friday, July 12, 2013 5:00:01 AM 
Subject: PyQt Digest, Vol 108, Issue 13 

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Today's Topics: 

1. Re: help a noob, Im a noob (David Boddie) 
2. Parent child relationship: child survives parent (Volker Pilipp) 
3. Re: Parent child relationship: child survives parent 
(Phil Thompson) 


---------------------------------------------------------------------- 

Message: 1 
Date: Thu, 11 Jul 2013 20:00:50 +0200 
From: David Boddie <david at boddie.org.uk> 
To: pyqt at riverbankcomputing.com 
Subject: Re: [PyQt] help a noob, Im a noob 
Message-ID: <201307112000.51212.david at boddie.org.uk> 
Content-Type: Text/Plain; charset="iso-8859-1" 

On Tue, 9 Jul 2013 15:00:25 -0600 (MDT), Brian McDonald wrote: 

> Just getting into programming in general. Loving python so far. I am 
> working on an application that will display database information on 
> screen. The idea is that some rows of database information will appear on 
> screen for 30 seconds, and then the next rows will appear. I think I have 
> made some pretty good headway getting the database connected and even 
> displaying data, but I am having a hell of a time getting the data to 
> refresh to a new query after 30 seconds. I feel like I must just be 
> calling the qtimer at the wrong point in the program. Or, perhaps I should 
> be using a "while" loop of some kind. Anyway, here is my code. Any help 
> would be sooo appreciated. 

Just quickly glancing at the code, I notice that you start the timer after 
the application has run. Have you tried starting the timer in your run() 
method? 

David 


------------------------------ 

Message: 2 
Date: Fri, 12 Jul 2013 09:30:46 +0200 
From: Volker Pilipp <volker.pilipp at dectris.com> 
To: pyqt at riverbankcomputing.com 
Subject: [PyQt] Parent child relationship: child survives parent 
Message-ID: 
<CAHio_yWovSQyiq1x1TMeWOGoG4pjM6179yCDELKgS0bXrj7_rQ at mail.gmail.com> 
Content-Type: text/plain; charset=ISO-8859-1 

I've got a little bit confused about ownership of objects in SIP As 
far as I understand, if ParentObject owns ChildObject, the destruction 
of ChildObject is left to c++ i.e. the c++ destructor of ParentObject 
is expected to destruct ChildObject. This behaviour may result in a 
seg fault if the python programmer does not make sure that ChildObject 
goes out of scope before ParentObject does. Indeed, there are many 
scenarios where this may happen accidentally. 

That's what I would like to have: The ChildObject keeps a reference 
on ParentObject that is released during destruction of ChildObject, 
where the Python destructor of ChildObject must not call the c++ 
destructor of the wrapped c++ instance (this is done during 
destruction of ParentObject). 
I am wondering if this behavior is possible to achieve in SIP. 


------------------------------ 

Message: 3 
Date: Fri, 12 Jul 2013 08:44:43 +0100 
From: Phil Thompson <phil at riverbankcomputing.com> 
To: Volker Pilipp <volker.pilipp at dectris.com> 
Cc: pyqt at riverbankcomputing.com 
Subject: Re: [PyQt] Parent child relationship: child survives parent 
Message-ID: <84fc10803f95f9bd598555abed8b40f7 at localhost> 
Content-Type: text/plain; charset=UTF-8 

On Fri, 12 Jul 2013 09:30:46 +0200, Volker Pilipp 
<volker.pilipp at dectris.com> wrote: 
> I've got a little bit confused about ownership of objects in SIP As 
> far as I understand, if ParentObject owns ChildObject, the destruction 
> of ChildObject is left to c++ i.e. the c++ destructor of ParentObject 
> is expected to destruct ChildObject. This behaviour may result in a 
> seg fault if the python programmer does not make sure that ChildObject 
> goes out of scope before ParentObject does. Indeed, there are many 
> scenarios where this may happen accidentally. 

If you are talking about QObject then you shouldn't get a segfault - you 
should get a Python exception. 

> That's what I would like to have: The ChildObject keeps a reference 
> on ParentObject that is released during destruction of ChildObject, 
> where the Python destructor of ChildObject must not call the c++ 
> destructor of the wrapped c++ instance (this is done during 
> destruction of ParentObject). 

The Python destructor will not call the C++ destructor if the C++ instance 
has a parent. If you think it does then provide a test case that 
demonstrates it. 

> I am wondering if this behavior is possible to achieve in SIP. 

Phil 


------------------------------ 

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