方法1

在qtdesigner中设置按钮图标的三个属性，normal off 、normal on和checkable=true。

from PyQt5.QtWidgets import *
from PyQt5.QtGui import *
from PyQt5.QtCore import *
from PyQt5 import uic
from switchBtn import Ui_Dialog


class Test(QDialog, Ui_Dialog):
    def __init__(self):
        super(Test, self).__init__()
        self.setupUi(self)

if __name__ == "__main__":
    app = QApplication([])
    window = Test()
    window.show()
    app.exec_()

方法2，通过切换图片

from PyQt5.QtWidgets import *
from PyQt5.QtGui import *
from PyQt5.QtCore import *
from PyQt5 import uic

from switchBtn import Ui_Dialog


class Test(QDialog, Ui_Dialog):
    def __init__(self):
        super(Test, self).__init__()
        self.setupUi(self)
        # uic.loadUi("switchBtn.ui", self)
        self.pushButton.clicked.connect(self.toggleIcon2)
        self.pushButton.setEnabled(True)  # false是点不动按钮
        self.btn_clicked = False

    def toggleIcon2(self):
        self.btn_clicked = not self.btn_clicked
        if self.btn_clicked:
            self.pushButton.setIcon(QIcon('switch_on.png'))
        else:
            self.pushButton.setIcon(QIcon('switch_off.png'))
        print(f"self.btn_clicked: {self.btn_clicked}")


if __name__ == "__main__":
    app = QApplication([])
    window = Test()
    window.show()
    app.exec_()

c++qt版本

bool btn_clicked = false;

    connect(ui->switchBtn,&QPushButton::clicked,this,[this](){
        btn_clicked = !btn_clicked;
        if (btn_clicked) {
            ui->switchBtn->setIcon(QIcon(":/imgs/switch_on.png"));
        } else {
            ui->switchBtn->setIcon(QIcon(":/imgs/switch_off.png"));
        }
        qDebug()<<"btn_clicked:"<<btn_clicked;
    });