How to signal slots in a GUI from a different process?

Question

Context: In Python a main thread spawns a 2nd process (using multiprocessing module) and then launches a GUI (using PyQt4). At this point the main thread blocks until the GUI is

Answer 1

A quite interesting topic. I guess having a signal that works between threads is a very useful thing. How about creating a custom signal based on sockets? I haven't tested this yet, but this is what I gathered up with some quick investigation:

class CrossThreadSignal(QObject):
    signal = pyqtSignal(object)
    def __init__(self, parent=None):
        super(QObject, self).__init__(parent)
        self.msgq = deque()
        self.read_sck, self.write_sck = socket.socketpair()
        self.notifier = QSocketNotifier(
                           self.read_sck.fileno(), 
                           QtCore.QSocketNotifier.Read
                        )
        self.notifier.activated.connect(self.recv)

    def recv(self):
        self.read_sck.recv(1)
        self.signal.emit(self.msgq.popleft())

    def input(self, message):
        self.msgq.append(message)
        self.write_sck.send('s')

Might just put you on the right track.