> *Forward multiple:* Plot graphs from the current set till the last set
> in the array. ie forward play from current graph till last graph.(Works,
> but when it reaches the last graph it exit from the app)
It can be confusing to use event loops in the way you are using them.
The danger is that the application's event loop will terminate.
My general advice would be to use only the event loop provided by
QApplication and write a widget that only includes the minimum needed
to show the dataset passed as an index.
Then add methods to step forward and backward.
Then think about adding methods to step forward and backward automatically,
using a QTimer.singleShot to queue the next dataset.
You will then be well on the way to implementing what you are asking for.