[PyKDE] qApp is a QApplication instance

Phil Thompson phil at riverbankcomputing.co.uk
Mon Mar 21 15:50:18 GMT 2005

> Phil Thompson <phil at riverbankcomputing.co.uk> wrote:
>>>>> Is this expected / wanted? I had expected to be able to access the
>>>>> Python
>>>>> instance of the application through the global qApp, not the
> QApplication.
>>>>> In Qt, I can down-cast the qApp pointer to my subclass to access my
>>>>> methods,
>>>>> how can I do the same in PyQt?
>>>> sys.modules['qt'].__dict__['qApp'] = A(sys.argv)
>>>> ...might do it. You have to make sure that this is done before the
>>>> other
>>>> modules that want to use it get imported.
>>> I'll try that, thanks.
>>> Would you consider this behaviour a bug, and in that case, is it
>>> feasable
>>> to
>>> fix it?
>> No, it's not a bug.
> Well, I'm trying, but it's almost impossible to do it. By the time the App
> constructor has executed, many modules are imported already. Even putting
> the sys.modules line at the top of A's constructor is not enough because
> of
> the fact that many modules are already imported. I even tried reload the
> modules but that caused other problems.
> I understand that you consider this not stricly a bug. But there *is* a
> need
> to access the application from everywhere without passing it around, and
> qApp exists exactly for that. In C++, you can downcast it to whatever app
> type you defined and use it. This is impossible with PyQt.

No it isn't - sip.cast()

> So, you should
> at
> least consider providing a different global for accessing the Python's
> application (pyApp?), as there is really no easy way to do it manually.


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