如何从不同的进程向 GUI 中的槽发出信号？

语境： 在 Python 中，主线程生成第二个进程（使用多处理模块），然后启动 GUI（使用 PyQt4）。此时主线程会阻塞，直到 GUI 关闭。第二个进程始终处于处理状态，理想情况下应以异步方式向 GUI 中的特定插槽发出信号。

问题： Python 和 PyQt4 中可以使用哪些方法/工具来实现这一目标以及如何实现？最好以软中断方式而不是轮询方式。

抽象地说，我能想到的解决方案是在主线程中实例化一个“工具/处理程序”，它从 GUI 实例中获取可用插槽，并与第二个进程中获取的信号连接，假设我向该工具提供了一些信息：预期或硬编码。这可以实例化为第三个进程/线程。

这是一个示例 Qt 应用程序，演示了从子进程向母进程中的槽发送信号。我不确定这是正确的方法，但它确实有效。

我将过程区分为mother and child，因为这个词parent已在 Qt 上下文中使用。
母进程有两个线程。母进程的主线程通过以下方式向子进程发送数据multiprocessing.Queue。子进程将处理后的数据和要发送到母进程的第二个线程的信号签名通过multiprocessing.Pipe。母进程的第二个线程实际上发出了信号。

Python 2.X、PyQt4：

from multiprocessing import Process, Queue, Pipe
from threading import Thread
import sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *

class Emitter(QObject, Thread):

    def __init__(self, transport, parent=None):
        QObject.__init__(self,parent)
        Thread.__init__(self)
        self.transport = transport

    def _emit(self, signature, args=None):
        if args:
            self.emit(SIGNAL(signature), args)
        else:
            self.emit(SIGNAL(signature))

    def run(self):
        while True:
            try:
                signature = self.transport.recv()
            except EOFError:
                break
            else:
                self._emit(*signature)

class Form(QDialog):

    def __init__(self, queue, emitter, parent=None):
        super(Form,self).__init__(parent)
        self.data_to_child = queue
        self.emitter = emitter
        self.emitter.daemon = True
        self.emitter.start()
        self.browser = QTextBrowser()
        self.lineedit = QLineEdit('Type text and press <Enter>')
        self.lineedit.selectAll()
        layout = QVBoxLayout()
        layout.addWidget(self.browser)
        layout.addWidget(self.lineedit)
        self.setLayout(layout)
        self.lineedit.setFocus()
        self.setWindowTitle('Upper')
        self.connect(self.lineedit,SIGNAL('returnPressed()'),self.to_child)
        self.connect(self.emitter,SIGNAL('data(PyQt_PyObject)'), self.updateUI)

    def to_child(self):
        self.data_to_child.put(unicode(self.lineedit.text()))
        self.lineedit.clear()

    def updateUI(self, text):
        text = text[0]
        self.browser.append(text)

class ChildProc(Process):

    def __init__(self, transport, queue, daemon=True):
        Process.__init__(self)
        self.daemon = daemon
        self.transport = transport
        self.data_from_mother = queue

    def emit_to_mother(self, signature, args=None):
        signature = (signature, )
        if args:
            signature += (args, )
        self.transport.send(signature)

    def run(self):
        while True:
            text = self.data_from_mother.get()
            self.emit_to_mother('data(PyQt_PyObject)', (text.upper(),))

if __name__ == '__main__':

    app = QApplication(sys.argv)
    mother_pipe, child_pipe = Pipe()
    queue = Queue()
    emitter = Emitter(mother_pipe)
    form = Form(queue, emitter)
    ChildProc(child_pipe, queue).start()
    form.show()
    app.exec_()

为了方便起见，还有 Python 3.X、PySide：

from multiprocessing import Process, Queue, Pipe
from threading import Thread

from PySide import QtGui, QtCore

class Emitter(QtCore.QObject, Thread):

    def __init__(self, transport, parent=None):
        QtCore.QObject.__init__(self, parent)
        Thread.__init__(self)
        self.transport = transport

    def _emit(self, signature, args=None):
        if args:
            self.emit(QtCore.SIGNAL(signature), args)
        else:
            self.emit(QtCore.SIGNAL(signature))

    def run(self):
        while True:
            try:
                signature = self.transport.recv()
            except EOFError:
                break
            else:
                self._emit(*signature)

class Form(QtGui.QDialog):

    def __init__(self, queue, emitter, parent=None):
        super().__init__(parent)
        self.data_to_child = queue
        self.emitter = emitter
        self.emitter.daemon = True
        self.emitter.start()
        self.browser = QtGui.QTextBrowser()
        self.lineedit = QtGui.QLineEdit('Type text and press <Enter>')
        self.lineedit.selectAll()
        layout = QtGui.QVBoxLayout()
        layout.addWidget(self.browser)
        layout.addWidget(self.lineedit)
        self.setLayout(layout)
        self.lineedit.setFocus()
        self.setWindowTitle('Upper')
        self.lineedit.returnPressed.connect(self.to_child)
        self.connect(self.emitter, QtCore.SIGNAL('data(PyObject)'), self.updateUI)

    def to_child(self):
        self.data_to_child.put(self.lineedit.text())
        self.lineedit.clear()

    def updateUI(self, text):
        self.browser.append(text[0])

class ChildProc(Process):

    def __init__(self, transport, queue, daemon=True):
        Process.__init__(self)
        self.daemon = daemon
        self.transport = transport
        self.data_from_mother = queue

    def emit_to_mother(self, signature, args=None):
        signature = (signature, )
        if args:
            signature += (args, )
        self.transport.send(signature)

    def run(self):
        while True:
            text = self.data_from_mother.get()
            self.emit_to_mother('data(PyQt_PyObject)', (text.upper(),))

if __name__ == '__main__':

    app = QApplication(sys.argv)
    mother_pipe, child_pipe = Pipe()
    queue = Queue()
    emitter = Emitter(mother_pipe)
    form = Form(queue, emitter)
    ChildProc(child_pipe, queue).start()
    form.show()
    app.exec_()