[PyQt] PyQt4 and Python 3.0

[Daniel Miller]

On Oct 7, 2008, at 12:54 PM, Phil Thompson wrote:
> On Tue, 7 Oct 2008 11:10:57 -0400, Daniel Miller  
> <daniel at keystonewood.com>
> wrote:
>>
>> - I am moving to PyQt4 because I need to use some of the new features
>> (the Graphics View Framework, for one). If I did not need these new
>> features in PyQt4 I'd be content to stay with PyQt3.
>>
>> ...
>>
>> Why should I rewrite an entire code base that is working fine and
>> does not need to be touched?
>
> Obviously you shouldn't if it is meeting your current and anticipated
> requirements.

It doesn't, see above.

> PyQt3 has always maintained backwards compatibility, so has PyQt4.  
> PyQt3 is
> not PyQt4. Likewise Qt3 is not Qt4. Granted, Trolltech produced a  
> Qt3=>Qt4
> migration tool, but then they have orders of magnitude more  
> development
> resources and charge a lot more money for their product.

You have a good point there. I should apologize for being so harsh. I  
guess I'm just frustrated that I have to do so much work to get to  
the point where I can actually start using PyQt4. I am really looking  
forward to it...

>> Not at all. You talk about PyQt4 like it's some entirely new beast
>> sharing next to nothing with the old PyQt3. Maybe that's how the
>> underlying implementation looks, but the end-user functionality is
>> 95% the same as it was in PyQt3--it still shows windows with widgets
>> on the screen, and users still interact with them in the same way
>> they did before. Adapting PyQt4 to the old PyQt3 API is not that
>> hard, it's just very tedious.
>
> I'm beginning to see where you are coming from. Apart from the fact  
> that
> there is tons more stuff in Qt4, which you probably haven't used if  
> you are
> just trying to emulate Qt3, I found that my programming style  
> changed once
> I became more familiar with Qt4. The model stuff just changes the  
> way you
> think about an application's architecture.

I've started to experiment with the model stuff. I have a framework  
similar to the Qt4 model API built around the old Qt3 table/listview/ 
combobox widgets, so it's mostly a matter of porting that framework  
to use the new Qt4 API.

>> However, it's much less tedious to implement a single new version of
>> qt.QSettings based on PyQt4.QtGui.QSettings than to rewrite every
>> place in my application that happens to touch the QSettings API (for
>> example).
>
> Every place? Surely you only use QSettings in one place?

Well, yes of course. Sorry for picking a bad example. How about  
QSplitter, QPushButton, QProgressBar, QPopumMenu, etc. Those are  
definitely used in many places, and the API for each of them changed.  
I realize this is not your fault--it was a decision made by  
Trolltech. However, I feel like they did more to help their users  
migrate old code bases to Qt4.


>>> Note that I wouldn't call the Q3Support classes a compatibility  
>>> layer.
>>
>> I agree. In a C++ app it might be possible (even simple?) to do
>> global find/replace ...
>
> You are seriously suggesting that PyQt4 should include a full  
> emulation of
> the PyQt3 API???

Why not? Is it too much to expect a widely used library to have  
backward compatibility between versions?

>> Why should I start with a blank piece of paper when I already have
>> 99% of what I need and it's all working correctly? You seem to think
>> there's value in rewriting code that is working perfectly. I see this
>> as a waste of my valuable time, which I could be spending
>> implementing new features.
>
> And if your design is adaptable and able to take new user  
> requirements, and
> new iterations of dependent technology easily then congratulations.  
> Except
> it isn't, otherwise we wouldn't be having this conversation and you
> wouldn't have calls to QSettings spread throughout your code.

Sorry, I picked a bad example; I don't have calls to QSettings  
everywhere.



>> Especially
>> not in the transition to Python 3, as it would require us to test two
>> new things at the same time: Python 3 and PyQtX.
>
> I know, that's what the thread on the mailing is all about. There  
> will be
> the old API and the new API and both will be available,  
> simultaneously, for
> Python2 and Python3. You choose which you want to develop against.

Great, that's what I was hoping would come out of this.


~~~~~~~~~~~

I tried to answer more of your questions, but the more I tried to  
take them seriously the more it just seemed like you were trying to  
blame my coding and design skills and not interested in the general  
point that I've been trying to make. So in an effort to minimize name  
calling and style bashing I'm going to stop here. Thanks a lot for  
your hard work on PyQt up to this point.

~ Daniel