PyQt4 [PyQt4]multiprocess 예제 코드

from PyQt4 import QtGui, QtCore
import multiprocessing as mp

def initChildProcess():
    app = QtGui.QApplication.instance()
    if app is not None:
        print "QApp already exists in child process."
    else:
        app = QtGui.QApplication([])
    
    win = QtGui.QMainWindow()
    win.setWindowTitle("Child Process")
    win.show()
    app.exec_()
    
def newProcess():
    proc = mp.Process(target=initChildProcess)
    proc.start()
    return proc
    
if __name__ == '__main__':
    ## This works as expected:
    #proc = newProcess()
    #app = QtGui.QApplication([])
    
    ## This causes crash:
    app = QtGui.QApplication([])
    proc = newProcess()
    
    win = QtGui.QMainWindow()
    win.setWindowTitle("Main Process")
    win.show()
    
    app.exec_()