I need to emit a signal periodically. A timer executes certain function, which emits the signal that I want. For some reason this function is not being emitted. I was able to reproduce the error on minimal code (see further down). If I do the same without the timer everything works:

from threading import Timer
import time
from PySide import QtCoreclass testSignals(QtCore.QObject):signal = QtCore.Signal();def __init__(self):QtCore.QObject.__init__(self)def run(self):self.signal.emit()class testConnection():@QtCore.Slot()def receiveMe(self):print('Signal received')# signal is emmited when data is changeddef __init__(self):test = testSignals()test.signal.connect(self.receiveMe)test.run();test = testConnection()

I was able to reproduce my problem in the following code:

from threading import Timer
import time
from PySide import QtCoreclass testSignals(QtCore.QObject):signal = QtCore.Signal();def __init__(self):self.is_running = FalseQtCore.QObject.__init__(self)self.start()def emitMe(self):self.is_running = Falseself.start()# print("emitMe")self.signal.emit()def start(self):if not self.is_running:self._timer = Timer(0.2, self.emitMe)self._timer.start()self.is_running = Truedef stop(self):self._timer.cancel()self.is_running = Falseclass testConnection():@QtCore.Slot()def receiveMe(self):print('Signal received')# signal is emmited when data is changeddef __init__(self):test = testSignals()test.signal.connect(self.receiveMe)test.start();time.sleep(2.0)test.stop();test = testConnection()

the phrase "Signal received" does not get printed on the screen.

As @ekhumoro said in the comments, QTimer helped a lot. I needed an event-loop. I'm posting the code to make the answer valid. I rewrote it using QTimer, which made everything simpler really. Note that I need to call QCoreApplication to run the threads. Again, this is just the minimal code to reproduce what I needed to do.

import time
from PySide import QtCore
from probeConnection import ProbeConnection class testSignals(QtCore.QObject):def __init__(self):self.timer = QtCore.QTimer()self.timer.timeout.connect(self.tick)self.start()def tick(self):print("tick")def getData(self):return time.strftime('%H:%M:%S')def start(self):self.timer.start(1000)def stop(self):self.timer.stop()class testConnection():def receiveMe(self):print('time: ' + self.test.getData())def __init__(self):self.test = testSignals()self.test.timer.timeout.connect(self.receiveMe)app = QtCore.QCoreApplication([])
test = testConnection()
timer = QtCore.QTimer()
timer.singleShot(4000,app.exit)
app.exec_()

it produces:

tick
time: 13:23:37
tick
time: 13:23:38
tick
time: 13:23:39
tick
time: 13:23:40