QMainWindow{
    border-image:url(./images/screen1.jpg);

}

QToolTip{
    border: 1px solid rgb(45, 45, 45);
    background: white;
    color: red;
}

class CommonHelper:
  def __init__(self):
    pass

  @staticmethod
  def readQss(style):
    with open(style, 'r') as f:
      return f.read()

app = QApplication(sys.argv)
  win = MainWindow()

  styleFile = './style.qss'
  qssStyle = CommonHelper.readQss(styleFile)
  win.setStyleSheet(qssStyle)

  win.show()
  sys.exit(app.exec_())

import sys
from PyQt5.QtWidgets import QMainWindow, QApplication, QVBoxLayout, QPushButton


class CommonHelper:
  def __init__(self):
    pass

  @staticmethod
  def readQss(style):
    with open(style, 'r') as f:
      return f.read()

class MainWindow(QMainWindow):
  def __init__(self, parent=None):
    super(MainWindow, self).__init__(parent)
    self.resize(477, 258)
    self.setWindowTitle("加载QSS文件")
    btn1 = QPushButton(self)
    btn1.setText('添加')
    btn1.setToolTip('测试提示')
    vbox = QVBoxLayout()
    vbox.addWidget(btn1)

    self.setLayout(vbox)


if __name__ == "__main__":
  app = QApplication(sys.argv)
  win = MainWindow()

  styleFile = './style.qss'
  qssStyle = CommonHelper.readQss(styleFile)
  win.setStyleSheet(qssStyle)

  win.show()
  sys.exit(app.exec_())