I have created a pyqt4 app and I want to make it so only one instance (of QApplication) is allowed to run.
The program reads and writes audio files, and if more than 1 instance is running, Windows (linux is fine) throws errors that 2 programs are trying to access the same files. I see a lot of java and C apps that will display a simple dialog if the program is already running, I just want to know how to do this in pyqt4.
A little help?
This kind of programming pattern is called a "singleton" instance or a "singleton application".
Usually it is done with a global mutex or by locking a file early in the life of the program. And when you program launches, if the file handle is already locked, then you exit.
Qt Solutions has it here: http://doc.qt.digia.com/solutions/4/qtsingleapplication/qtsingleapplication.html
It would probably take a bit of work to get those global mutexes/locks to work in pyqt, since pyqt doesn't have the qt-solutions part in it yet as far as I could tell.
Here is an alternative that uses a cross platform python script:
Python: single instance of program
Hope that helps.
Thanks. I Used https://gitorious.org/qsingleapplication/qsingleapplication/source/ca13324b0f5bdfcaf4e379a78108f0bd85fed98a:qSingleApplication.py#L66 And Called QSingleApplication On My MainWindow And Works Fine
