title: Update stylesheet without losing original style
body: <p>I am creating qpushbuttons with a certain style and then updating the style sheet to color them later on. However when I do this it overwrites the original style. Is there a way I can update or append to the object's stylesheet without losing it or having to redefine everything again? </p>
  
  <pre><code>import sys
  from PyQt5 import QtCore, QtWidgets
  from PyQt5.QtWidgets import QMainWindow, QLabel, QGridLayout,QPushButton, QMenu, QApplication, QWidget, QInputDialog, QLineEdit
  from PyQt5.QtCore import QSize, QCoreApplication, Qt, QLine, QPoint
  from PyQt5.QtGui import QPainter, QPen, QFont,QPainter, QPainterPath, QPixmap
  
  
  class MainWindow(QMainWindow):
      def __init__(self):
          QMainWindow.__init__(self)
          self.setMinimumSize(QSize(400, 400))   
  
          color = QPushButton('color', self)
          color.clicked.connect(self.color)
          color.resize(100,115)
          color.move(0, 100)
  
          buttons= ['button1','button2','button3']
          self.pybutton = {}
          x=0
          t = 0
          for i in buttons:
              t = t + 100
              x+=1
              self.pybutton[str(x)] = QPushButton(i, self) 
              self.pybutton[str(x)].setObjectName('btn' + str(x))
              self.pybutton[str(x)].resize(100,100)
              self.pybutton[str(x)].move(400-int(t),100)
              self.pybutton[str(x)].setStyleSheet('QPushButton {max-width: 75px;text-align:center;padding-left: 20px; max-height: 60px; font-size: 20px;}')
          self.statusBar()
      def status(self):
          sender = self.sender()
          print('PyQt5 button click')
          self.statusBar().showMessage(sender.text() + ' was pressed')
  
      def color(self):
          for i in self.pybutton:
              self.pybutton[str(i)].objectName()
              if self.pybutton[str(i)].objectName() == 'btn1':
                  self.pybutton[str(i)].setStyleSheet("background-color: green")
              else:
                  self.pybutton[str(i)].setStyleSheet("background-color: red")    
  
  if __name__ == "__main__":
      app = QtWidgets.QApplication(sys.argv)
      mainWin = MainWindow()
      mainWin.show()
      sys.exit( app.exec_() )
  </code></pre>