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

class RadioDemo(QWidget):
 def __init__(self,parent=None):
  super(RadioDemo,self).__init__(parent)
  #水平布局
  layout=QHBoxLayout()


  self.btn1=QRadioButton('Button1')
  #默認選中btn1
  self.btn1.setChecked(True)
  #toggled信號與槽函數(shù)綁定
  self.btn1.toggled.connect(lambda :self.btnstate(self.btn1))
  layout.addWidget(self.btn1)

  self.btn2 = QRadioButton('Button2')
  self.btn2.toggled.connect(lambda: self.btnstate(self.btn2))
  layout.addWidget(self.btn2)

  self.setLayout(layout)
  self.setWindowTitle('RadioButton demo')

 def btnstate(self,btn):
 #輸出按鈕1與按鈕2的狀態(tài)，選中還是沒選中
  if btn.text()=='Button1':
   if btn.isChecked()==True:
    print(btn.text()+"is selected")
   else:
    print(btn.text()+"is deselected")

  if btn.text()=="Button2":
   if btn.isChecked() == True:
    print(btn.text() + "is selected")
   else:
    print(btn.text() + "is deselected")
if __name__ == '__main__':
 app=QApplication(sys.argv)
 radioDemo=RadioDemo()
 radioDemo.show()
 sys.exit(app.exec_())

self.btn1.setChecked(True)

self.btn1.toggled.connect(lambda :self.btnstate(self.btn1))
self.btn1.toggled.connect(lambda :self.btnstate(self.btn1))