class Counter(QThread):
#: this signal is emitted whenever the worker has performed a single
# step
progress = Signal(int)
#: this signal publishes the minimum amount of required steps
minimumChanged = Signal(int)
#: this signal publishes the maximum amount of required steps
maximumChanged = Signal(int)
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)
def run(self):
# published our minimum and maximum values. A real worker thread
# would typically calculate the number of required steps
self.minimumChanged.emit(1)
self.maximumChanged.emit(self.maximum)
# now do our work, which is simply counting in this example
for i in range(1, self.maximum + 1):
self.progress.emit(i)
# check, if the thread is still permitted to run. This test
# fails, if the single resource of this semaphore is acquired,
# which is done by the stop() method, just to stop work at
# precisly this point
if self._run_semaphore.available() == 0:
# release the resource again to enable a restart of this worker
self._run_semaphore.release(1)
# break the loop. A real worker would typically roll back
# his work to leave the state of the application unchanged,
# because the work was forcibly interrupted.
break
# simulate some heavy work
self.msleep(100)
def stop(self):
# acquire the single resource of our run semaphore. No resources
# are now available anymore, so next time, run() checks the number
# of available resources, it sees none and returns.
self._run_semaphore.acquire(1)
class Counter(QThread):
#: this signal is emitted whenever the worker has performed a single
# step
progress = Signal(int)
#: this signal publishes the minimum amount of required steps
minimumChanged = Signal(int)
#: this signal publishes the maximum amount of required steps
maximumChanged = Signal(int)
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)
def run(self):
# published our minimum and maximum values. A real worker thread
# would typically calculate the number of required steps
self.minimumChanged.emit(1)
self.maximumChanged.emit(self.maximum)
# now do our work, which is simply counting in this example
for i in range(1, self.maximum+1):
self.progress.emit(i)
# check, if the thread is still permitted to run. This test
# fails, if the single resource of this semaphore is acquired,
# which is done by the stop() method, just to stop work at
# precisly this point
if self._run_semaphore.available() == 0:
# release the resource again to enable a restart of this worker
self._run_semaphore.release(1)
# break the loop. A real worker would typically roll back
# his work to leave the state of the application unchanged,
# because the work was forcibly interrupted.
break
# simulate some heavy work
self.msleep(100)
def stop(self):
# acquire the single resource of our run semaphore. No resources
# are now available anymore, so next time, run() checks the number
# of available resources, it sees none and returns.
self._run_semaphore.acquire(1)
