I used Qt4Designer to design an application UI.
I did this but when I was converting it to a .py file via pyuic4 as below:
pyuic4 myui.ui > myui.py
I facet to an error that said: Error: Q3Support widgets are not supported by PyQt4.
what is this error's reason?
Can we use all widgets placed in designer? for example KDatePicker, Q3Table and etc.
The Q3Support classes are only there to help with porting a Qt3 application to Qt4. There's absolutely no reason to use them in new code. And in any case, they will be dropped completely for Qt5 (which is not far away now).
There's nothing much to add regarding the error message you got, as it could hardly be clearer. The Q3Support widgets are not supported by PyQt4. Which is to say, PyQt4 simply does not wrap any of those particular Qt classes.
As for the KDE widgets: they are not directly supported by PyQt either.
To use them with python, you would require PyKDE4 - and the ui files would need to be compiled with pykdeuic4.