def __init__(self, maximum, parent=None):
QThread.__init__(self, parent)
self.maximum = maximum
# this semaphore is used to stop the thread from outside. As long
# as the thread is permitted to run, it has yet a single resource
# available. If the thread is stopped, this resource is acquired,
# and the thread breaks its counting loop at the next iteration.
self._run_semaphore = QSemaphore(1)
