title: How do I properly perform multiprocessing from PyQt?
body: <p>I create a button and try to run multiprocessing when I click button ,</p>
  
  <p>but the UI is become blocked . I hope process run in backgorund .</p>
  
  <p>How can I fix it ?</p>
  
  <pre><code>from PySide2 import QtCore,QtGui,QtWidgets
  import sys
  import multiprocessing
  from threading import Timer
  class TTT(multiprocessing.Process):
      def __init__(self):
          super(TTT, self).__init__()
          self.daemon = True
      def run(self):
          while True:
              t = Timer(5, self.doSomething)
              t.start()
              t.join()
  
      def doSomething(self):
          try:
              print('123')
          except Exception as e:
              print(e)
  
  class MainWindow(QtWidgets.QMainWindow):
      def __init__(self, parent=None):
          super(MainWindow, self).__init__(parent)
          btn = QtWidgets.QPushButton('run process')
          btn.clicked.connect(self.create_process)
          self.setCentralWidget(btn)
  
      def create_process(self):
          QtWidgets.QMessageBox.information(self,'hhh','hhh')
          t = TTT()
          t.start()
          t.join()
  
  if __name__=="__main__":
      app=QtWidgets.QApplication(sys.argv)
      ex = MainWindow()
      ex.show()
      sys.exit(app.exec_())
  </code></pre>