Solve the problem that QToolButton cannot be used in pyqt5

When you use QToolButton in pyqt, you must add this sentence if you want to achieve different functions by pressing and lifting:

self.btn_1.setCheckable(True)

The basic code for setting up an toolbutton is:

 self.btn_1 = QToolButton(self)
 self.btn_1.setText('start')
 self.btn_1.setCheckable(True)
 self.btn_1.clicked.connect(self.btn_1_function)
 
 
def btn_1_function(self):
  if self.btn_1.isChecked():
    pass
  else:
    pass