定时器QTimer

 import sys
 from PyQt5.QtCore import QTimer, Qt
 from PyQt5.QtWidgets import QApplication, QWidget, QPushButton, QLabel, QVBoxLayout

 class Demo(QWidget):
     def __init__(self):
         super(Demo, self).__init__()
         self.label = QLabel('', self)
         self.label.setAlignment(Qt.AlignCenter)

         self.step = 0

         self.timer = QTimer(self)  #实例化定时器
         self.timer.timeout.connect(self.update_func)  #设置定时执行的函数

         self.ss_button = QPushButton('Start', self)
         self.ss_button.clicked.connect(self.start_stop_func)

         self.v_layout = QVBoxLayout()
         self.v_layout.addWidget(self.label)
         self.v_layout.addWidget(self.ss_button)

         self.setLayout(self.v_layout)

     def start_stop_func(self):
         if not self.timer.isActive():
             #self.timer.isActive()  返回定时器是否激活  Ture激活
             self.ss_button.setText('Stop')
             self.timer.start(100)    #启动定时器，时间间隔100毫秒
         else:
             self.ss_button.setText('Start')
             self.timer.stop()   #停止定时器

     def update_func(self):
         self.step += 1
         self.label.setText(str(self.step))

 if __name__ == '__main__':
     app = QApplication(sys.argv)
     demo = Demo()
     demo.show()
     sys.exit(app.exec_())