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

    Form = QMdiArea()
    Form.resize(1000, 400)

    win = n_window()
    win.maximumSize()
    sub = QMdiSubWindow()
    sub.setWidget(win)
    sub.resize(380, 150)
    # sub.show()

    win2 = n_window()
    sub2 = QMdiSubWindow()
    sub2.setWidget(win2)
    sub2.resize(380, 150)
    Form.addSubWindow(sub)
    # Form.addSubWindow(sub2)
    Form.show()
    sub2.show()

    sys.exit(app.exec_())