Preventing tread collisions

Wanderer wanderer at dialup4less.com
Wed Dec 12 21:11:35 CET 2012


I have a program that has a main GUI and a camera. In the main GUI, you can manipulate the images taken by the camera. You can also use the menu to check the camera's settings. Images are taken by the camera in a separate thread, so the long exposures don't block the GUI. I block conflicts between the camera snapshot thread and the main thread by setting a flag called self.cameraActive. I check to see if the cameraActive flag is false and set the cameraActive to True just before starting the thread. I generate an event on exiting the thread which sets the cameraActive flag to False. I also check and set and reset the flag in all the menu commands that access the camera. Like this.

    def onProperties(self, event):
        """ Display a message window with the camera properties
        event -- The camera properties menu event
        """
        # Update the temperature
        if not self.cameraActive:
            self.cameraActive = True
            self.camera.getTemperature()
            camDict = self.camera.getPropertyDict()
            self.cameraActive = False
        else:
            camDict = {'Error': 'Camera Busy'}
        dictMessage(camDict, 'Camera Properties')

This works but my question is, is there a better way using semaphores, locks or something else to prevent collisions between threads?

Thanks



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