3、取事件的的傳送者（此例為各個按鈕）的文字： self.sender().text()

#簡易計算器
import sys
from PyQt5 import QtWidgets,QtCore,QtGui
class Example(QtWidgets.QWidget):
 def __init__(self):
  super(Example, self).__init__()
  self.initUI()
  self.reset()
 def initUI(self):
  self.setWindowTitle('簡易計算器')
  grid = QtWidgets.QGridLayout()
  self.display = QtWidgets.QLineEdit('0')
  self.display.setFont(QtGui.QFont("Times", 20))
  self.display.setReadOnly(True)
  self.display.setAlignment(QtCore.Qt.AlignRight)
  self.display.setMaxLength(15)
  grid.addWidget(self.display,0,0,1,4)
  names = ['Clear', 'Back', '', 'Close', 
    '7', '8', '9', '/',
    '4', '5', '6', '*', 
    '1', '2', '3', '-',
    '0', '.', '=', '+']
  pos = [(0, 0), (0, 1), (0, 2), (0, 3),
    (1, 0), (1, 1), (1, 2), (1, 3),
    (2, 0), (2, 1), (2, 2), (2, 3),
    (3, 0), (3, 1), (3, 2), (3, 3 ),
    (4, 0), (4, 1), (4, 2), (4, 3)]
  c = 0
  for name in names:
   button = QtWidgets.QPushButton(name)
   button.setFixedSize(QtCore.QSize(60,30))
   button.clicked.connect(self.buttonClicked) # 給每個按鈕設定訊號/槽
   if c == 2:
    pass
    #grid.addWidget(QtWidgets.QLabel(''), 0, 2) #替換 第三個按鈕 為 文字標籤！
   else: 
    grid.addWidget(button, pos[c][0]+1, pos[c][1])
   c = c + 1
  self.setLayout(grid)
 def buttonClicked(self): 
  #sender = self.sender(); # 確定訊號傳送者
  #self.display.setText(sender.text())
  text = self.sender().text()
  if text in '+-*/':
   self.history.append(self.number) # 數字入棧
   self.history.append(text) # 運算子入棧
   self.operator = text # 設定當前運算子
   self.number = "" # 數字清空
   self.numberType = "int"
   return
  elif text == "=":
   self.calculate() # 計算
  elif text == "Back":
   pass
  elif text == "Clear":
   self.reset()
  elif text == "Close":
   self.close()
  elif text == ".":
   if self.numberType == "int":
    self.number += text
    self.numberType = "float"
  else:
   self.number = self.number + text if self.number != "0" else text
  self.display.setText(self.number)
 def calculate(self):
  pass
 def reset(self):
  self.number = "0"
  self.result = 0
  self.history = []
  self.operator = '' # +,-,*,/
  self.numberType = 'int' # int與float兩種，如果輸入了小數點則為實數
app = QtWidgets.QApplication(sys.argv)
ex = Example()
ex.show()
sys.exit(app.exec_())