pyqt5中QThread在使用时出现重复emit的实例

# -*- coding: utf-8 -*-import sysimport timefrom PyQt5.QtWidgets import *from PyQt5.QtCore import *  class MainUi(QWidget):  def __init__(self):    super(MainUi, self).__init__()    self.resize(400, 200)    self.setWindowTitle('QThread例子')     # 实例化多线程对象    self.thread = Worker()     # 实例化列表控件与按钮控件    self.listFile = QListWidget()    self.btnStart = QPushButton('开始')    self.btn_over = QPushButton('结束')     # 把控件放置在栅格布局中    layout = QGridLayout(self)    layout.addWidget(self.listFile, 0, 0, 1, 2)    layout.addWidget(self.btnStart, 1, 0)    layout.addWidget(self.btn_over, 1, 1)     # 信号与槽函数的连接    self.btnStart.clicked.connect(self.slotStart)    self.btn_over.clicked.connect(self.slot_btn_over)     # 建立线程信号的槽连接    self.thread.trigger.connect(self.slotAdd)   def slotAdd(self, msg):    print(msg)    if int(msg) % 2 == 0:      self.listFile.addItem(msg)    else:      pass    self.thread.exit()   def slotStart(self):    self.btnStart.setEnabled(False)    self.thread.start()   def slot_btn_over(self):    self.btnStart.setEnabled(True)    self.thread.terminate()    self.thread.num = 0  class Worker(QThread):  trigger = pyqtSignal(str)  num = 0   def __init__(self):    super(Worker, self).__init__()   def run(self):    while True:      print('num= ', self.num)      if self.num % 2 == 0:        self.trigger.emit(str(50))      elif self.num == 200:        self.num = 0      else:        pass      time.sleep(0.1)      self.num += 1  if __name__ == '__main__':  app = QApplication(sys.argv)  w = MainUi()  w.show()  sys.exit(app.exec_())