Use QProcess to run a program

if self.mosquitto_process is None:
    self.mosquitto_process = QProcess()
self.mosquitto_process.start("mosquitto.cmd")

self.port = utils.pick_free_port()
    _logger().debug('starting server process: %s',
                    ' '.join([self._interpreter, server.__file__,
                              str(self.port)]))
    self._process = QtCore.QProcess()
    self._process.readyRead.connect(self._on_ready_read)
    self._process.setProcessChannelMode(self._process.MergedChannels)
    self._process.finished.connect(self._on_finished)
    self._process.stateChanged.connect(self._on_state_changed)
    self._process.start(
        self._interpreter, (server.__file__, str(self.port)))

proc = QProcess()
    proc.start(*py_proc('print("Hello World")'))
    dev = qtutils.PyQIODevice(proc)
    assert not dev.closed
    with pytest.raises(OSError) as excinfo:
        dev.seek(0)
    assert str(excinfo.value) == 'Random access not allowed!'
    with pytest.raises(OSError) as excinfo:
        dev.tell()
    assert str(excinfo.value) == 'Random access not allowed!'
    proc.waitForFinished(1000)
    proc.kill()
    assert bytes(dev.read()).rstrip() == b'Hello World'

References
https://programtalk.com/python-examples/PyQt5.QtCore.QProcess/