如何让widgets与PyQt5中的窗口一起缩放？

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

class MyWindow(QMainWindow):
    def __init__(self):
        super().__init__()

        layout = QVBoxLayout()
        button1 = QPushButton("Button 1")
        button2 = QPushButton("Button 2")
        layout.addWidget(button1)
        layout.addWidget(button2)

        central_widget = QWidget()
        central_widget.setLayout(layout)
        self.setCentralWidget(central_widget)

if __name__ == "__main__":
    app = QApplication(sys.argv)
    window = MyWindow()
    window.show()
    sys.exit(app.exec_())

button1.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Expanding)
button2.setSizePolicy(QSizePolicy.Expanding, QSizePolicy.Expanding)

def resizeEvent(self, event):
    button1.resize(event.size().width() / 2, event.size().height())
    button2.resize(event.size().width() / 2, event.size().height())