单击按钮或操作菜单时，PyQt5窗口崩溃

Question

从New单击动作MenuBar时，我试图启动新对话框，但是当我单击该动作时，程序崩溃了，并且没有打开新窗口。

下面是我从QT Designer中提取的代码，然后根据需要进行了更改。

from PyQt5.QtWidgets import QMainWindow, QApplication
from PyQt5 import QtCore, QtWidgets

import sys


class main_window(QtWidgets.QMainWindow):

    switch_window = QtCore.pyqtSignal(str)

    def __init__(self):
        QtWidgets.QMainWindow.__init__(self)
        QtWidgets.QWidget.__init__(self)
        self.setObjectName("mainWindow")
        self.resize(792, 600)
        self.centralwidget = QtWidgets.QMainWindow(self)
        self.centralwidget.setObjectName("centralwidget")
        self.splitter = QtWidgets.QSplitter(self.centralwidget)
        self.splitter.setGeometry(QtCore.QRect(20, 80, 180, 20))
        self.splitter.setOrientation(QtCore.Qt.Horizontal)
        self.splitter.setObjectName("splitter")
        self.setCentralWidget(self.centralwidget)
        self.menubar = QtWidgets.QMenuBar(self)
        self.menubar.setGeometry(QtCore.QRect(0, 0, 792, 21))
        self.menubar.setObjectName("menubar")
        self.menuFile = QtWidgets.QMenu(self.menubar)
        self.menuFile.setObjectName("menuFile")
        self.menuView = QtWidgets.QMenu(self.menubar)
        self.menuView.setObjectName("menuView")
        self.setMenuBar(self.menubar)
        self.statusbar = QtWidgets.QStatusBar(self)
        self.statusbar.setObjectName("statusbar")
        self.setStatusBar(self.statusbar)
        self.actionNew = QtWidgets.QAction(self)
        self.actionNew.setObjectName("actionNew")
        self.menuFile.addSeparator()
        self.menuFile.addAction(self.actionNew)
        self.menubar.addAction(self.menuFile.menuAction())
        self.menubar.addAction(self.menuView.menuAction())

        self.setWindowTitle("MainWindow")
        self.menuFile.setTitle("File")
        self.menuView.setTitle("View")
        self.actionNew.setText("LandForm")

        self.actionNew.triggered.connect(self.switch)

    def switch(self):
        self.switch_window.emit()


class land_form(QtWidgets.QWidget):

    def __init__(self):
        QtWidgets.QWidget.__init__(self)

        self.setObjectName("LandForm")
        self.resize(660, 482)
        self.gridLayout = QtWidgets.QGridLayout(self)
        self.gridLayout.setObjectName("gridLayout")
        self.LandFormData = QtWidgets.QListView(self)
        self.LandFormData.setObjectName("LandFormData")
        self.gridLayout.addWidget(self.LandFormData, 0, 0, 1, 5)

        self.setWindowTitle("Dialog")


class MyForm:
    def __init__(self):
        pass

    def main_window(self):
        self.main_window_create = main_window()
        self.main_window_create.switch_window.connect(self.land_form)
        self.main_window_create.show()

    def land_form(self):
        self.land_form_create = land_form()
        self.land_form_create.show()


def main():
    main_app = QtWidgets.QApplication(sys.argv)
    main_my_app = MyForm()
    main_my_app.main_window()
    sys.exit(main_app.exec_())


if __name__ == "__main__":
    main()