import sys

 from PyQt5.QtCore import Qt, QThread,pyqtSignal

 from PyQt5.QtWidgets import QApplication, QWidget, QPushButton, QLabel, QVBoxLayout,QHBoxLayout

 class Demo(QWidget):

     def __init__(self):

         super(Demo, self).__init__()

         self.button = QPushButton('开始', self)

         self.button.clicked.connect(self.count_func)

         self.button_2 = QPushButton('停止', self)

         self.button_2.clicked.connect(self.stop_count_func)

         self.label = QLabel('', self)

         self.label.setAlignment(Qt.AlignCenter)

         self.my_thread = MyThread()#实例化线程对象

         self.my_thread.my_signal.connect(self.set_label_func)

20         #线程自定义信号连接的槽函数

         self.h_layout = QHBoxLayout()

         self.v_layout = QVBoxLayout()

         self.h_layout.addWidget(self.button)

         self.h_layout.addWidget(self.button_2)

         self.v_layout.addWidget(self.label)

         self.v_layout.addLayout(self.h_layout)

         self.setLayout(self.v_layout)

     def stop_count_func(self):

         self.my_thread.is_on = False

         self.my_thread.count = 0

     def count_func(self):

         self.my_thread.is_on = True

         self.my_thread.start()#启动线程

     def set_label_func(self, num):

         self.label.setText(num)

         #由于自定义信号时自动传递一个字符串参数，所以在这个槽函数中要接受一个参数

 class MyThread(QThread):#线程类

     my_signal = pyqtSignal(str)  #自定义信号对象。参数str就代表这个信号可以传一个字符串

     def __init__(self):

         super(MyThread, self).__init__()

         self.count = 0

         self.is_on = True

     def run(self): #线程执行函数

         while self.is_on :

             print(self.count)

             self.count += 1

             self.my_signal.emit(str(self.count))  #释放自定义的信号

             #通过自定义信号把str(self.count)传递给槽函数

             self.sleep(1)  #本线程睡眠n秒【是QThread函数】

 if __name__ == '__main__':

     app = QApplication(sys.argv)

     demo = Demo()

     demo.show()

     sys.exit(app.exec_())