PyQt5 daughter window

[Analeea]

Help me create a subsidiary window that will close with him when the main window is closed, the bottom window itself must be different.

Unfortunately, I only know how to create a regular window.

class MainWindow(QMainWindow):
    def __init__(self):
        super(MainWindow, self).__init__()
    self.setWindowTitle("Lab 2-3")

    self.centralWidget = QWidget(self)
    self.setCentralWidget(self.centralWidget)
    self.grid_layout = QGridLayout(self.centralWidget)

    self.setGeometry(590, 300, 480, 215)
    self.setStyleSheet("background : white;")

[Avante]

Try this:

import sys
from PyQt5.Qt import *
class Window_2(QMainWindow):                             # !!! QMainWindow

def init(self, parent=None):

super().init(parent)                         # !!! parent

self.setWindowTitle("Window_2")

self.resize(200, 215)
class MainWindow(QMainWindow):

def init(self):

super(MainWindow, self).init()

self.setWindowTitle("Lab 2-3")

self.setGeometry(590, 300, 480, 215)

self.setStyleSheet("background : white;")
    self.centralWidget = QWidget(self)
    self.setCentralWidget(self.centralWidget)

    self.button = QPushButton('Создать второе окно')
    self.button.clicked.connect(self.create_window) 
    
    self.grid_layout = QGridLayout(self.centralWidget)
    self.grid_layout.addWidget(self.button)
    
def create_window(self):
    self.window = Window_2(self)                        # !!! self
    self.window.show()

if name == "main":

app = QApplication(sys.argv)

window = MainWindow()

window.show()

sys.exit(app.exec_())