to create a circle progressbar

[wagmare]

You could also go for a simple way... Use a busy cursor animated gif and show that

yeah its a good way ... but i am aiming like this .. when user selects some operation
make the screen black and in middle rotate the progressBar circle until the operatio completes ... it will be good task ...?

[aamer4yu]

make the screen black and in middle rotate the progressBar circle until the operatio completes ... it will be good task ...?

You can show a widget fullscreen with semi transparency. In the middle of the widget you can have a QLabel running the gif as a movie, or you will need to do you custom painting.
Whether to add painting in the full screen widget or create a custom widget and then add it to the full screen widget is your choice.