如何制作秒表

试试这样：

import sys
from datetime import datetime
from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.Qt import *


class MainWindow(QtWidgets.QWidget):
    def __init__(self):
        super().__init__()
        
        self.temp = 0
        
        self.label = QLabel("00:00:00", alignment=Qt.AlignCenter)
        self.label.setFont(QtGui.QFont("Rio Glamour personal use", 30, QtGui.QFont.Bold))
        self.label.setStyleSheet("color: #4B6587;")
        
        self.button_start = QtWidgets.QPushButton('Старт')
        self.button_start.clicked.connect(self.func_start)

        self.button_continue = QtWidgets.QPushButton('Продолжить')
        self.button_continue.clicked.connect(self.func_continue)

        self.button_reset = QtWidgets.QPushButton('Сбросить')
        self.button_reset.clicked.connect(self.func_reset)
        
        layout = QGridLayout(self)
        layout.addWidget(self.label, 0, 0, 1, 2)
        layout.addWidget(self.button_start, 1, 0, 1, 2)
        layout.addWidget(self.button_continue, 2, 0, 1, 1)
        layout.addWidget(self.button_reset, 2, 1, 1, 1)        
        
        self.button_continue.hide()
        self.button_reset.hide()
        
        self.timer = QtCore.QTimer()
        self.timer.setInterval(1000)
        self.timer.timeout.connect(self.displayTime)        
        
    def func_start(self):
        if self.button_start.text() == 'Старт':
            self.timer.start()
            self.button_start.setText('Стоп')
        else:
            self.timer.stop()
            self.button_start.setText('Старт')
            self.button_start.hide()
            self.button_continue.show()
            self.button_reset.show()            
         
    def func_continue(self):
        self.timer.start()
        self.button_start.setText('Стоп') 
        self.button_start.show()
        self.button_continue.hide()
        self.button_reset.hide() 

    def func_reset(self):
        self.temp = 0
        self.label.setText("00:00:00") 
        self.button_start.setText('Старт') 
        self.button_start.show()
        self.button_continue.hide()
        self.button_reset.hide()         

    def displayTime(self):
        f_temp = datetime.utcfromtimestamp(self.temp).strftime("%H:%M:%S")
        self.label.setText(f_temp)
        self.temp += 1    
        
        
if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    app.setStyle("Fusion")
    w = MainWindow()
    w.setWindowTitle('Секундомер')
    w.resize(300, 150)
    w.show()
    sys.exit(app.exec_())