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('0', 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_())