PyQt5实现从主窗口打开子窗口的方法

#-*- coding:utf-8 -*-
from PyQt5.QtWidgets import QMainWindow, QApplication
from window import Ui_MainWindow
from child import Ui_Child
import sys
 
class Main(QMainWindow,Ui_MainWindow):
  def __init__(self):
    super(Main, self).__init__()
    self.setupUi(self)
 
class Child(QMainWindow,Ui_Child):
  def __init__(self):
    super(Child, self).__init__()
    self.setupUi(self)
    self.pushButton.clicked.connect(self.close)
  def OPEN(self):
    self.show()
 
if __name__ =="__main__":
  app = QApplication(sys.argv)
  main = Main()
  ch = Child()
  main.show()
  main.pushButton.clicked.connect(ch.OPEN)
  sys.exit(app.exec_())