Python 如何在 PyQt 中连接三个或更多窗口

我有一个复杂的程序，需要连接多个窗口.不幸的是，我似乎没有完全理解这样做所需的概念/步骤，因此，如果有人能很好地解释这些步骤/过程，我会得到额外的分数.在我当前的程序中，我有一个项目列表.一旦我通过将它们移到右边的列表小部件来 Select 它们，我需要它们转到第三个窗口.第三个窗口应通过单击第二个窗口上的点来激活.程序运行并适当显示第二个窗口，但dots按钮的信号/插槽连接不起作用.然而，其余的代码仍在运行，因为如果我切换工具箱以显示第三个窗口，则该部分的执行情况与预期一致.下面是我的代码，同样，没有返回任何错误，但单击第二个窗口上的点按钮没有任何作用.

还有一个问题，我是在第二个类中实例化第三个窗口，还是只在主窗口中实例化？再一次，我正在努力完全理解这个过程，我还需要多次这样做.

from PyQt5.QtWidgets import QApplication, QWidget, QLabel, QPushButton, QListWidget, QLineEdit, QTextEdit, QGridLayout, QHBoxLayout, QVBoxLayout, QSizePolicy, QFileDialog, QTabWidget, QCheckBox
import PyQt5.QtGui as qtg
import glob
import os
from PyQt5.QtCore import Qt, QSettings
import inspect
from PyQt5 import QtCore
import pandas as pd 
import pathlib
import pyreadstat
import json


class ThirdWindow(QWidget):
    def __init__(self):
        super().__init__()
        
        
        self.layout = QGridLayout()
        self.setLayout(self.layout)
        self.allVariables = QListWidget()
        self.variablesSelected = QListWidget()
        #self.allVariables.insertItem(0, 'Hello')
        self.layout.addWidget(self.allVariables, 1,0)
        self.layout.addWidget(self.variablesSelected, 1, 1)
        
    def setItems(self, items):
        self.allVariables.clear()
        for item in items:
            self.allVariables.addItem(item)
     
    
     
class SecondWindow(QWidget):
    def __init__(self):
        super().__init__()
        
        ##not sure if I am supposed to instantiate this here or only in the main window class
        self.thirdWindow = ThirdWindow()
        
    
        self.layout = QGridLayout(self)
        self.by = QLabel("By")
        self.byVariables = QLineEdit()
        self.byButton = QPushButton("...")
        self.layout.addWidget(self.by, 1, 0)
        self.layout.addWidget(self.byVariables, 2, 0)
        self.layout.addWidget(self.byButton, 2, 1)
        
       
    def seconddWindowConnections(self):
        self.byButton.clicked.connect(self.show_third_window)
        #self.buttons['Toolkit'].clicked.connect(self.show_new_window)   
        
    def show_third_window(self):
        self.thirdWindow.show()
        
class MainWindow(QWidget):
    def __init__(self):
        super().__init__()

        # Add a title
        self.setWindowTitle("GUI Querying Program")

        self.layout = QHBoxLayout()
        self.setLayout(self.layout)
        self.initUI()
        self.setButtonConnections()
        
        self.sw = SecondWindow()
        self.tw = ThirdWindow()
        

    def initUI(self):
        subLayouts = {}

        subLayouts['LeftColumn'] = QGridLayout()
    
        self.layout.addLayout(subLayouts['LeftColumn'],1)
        
        # Buttons
        self.buttons = {}
        self.buttons['addVariable'] = QPushButton('>')
        self.buttons['removeVariable'] = QPushButton('<')
        self.buttons['Toolkit'] = QPushButton('Toolkit')
        
        
        self.variables = QListWidget()
        self.selectedVariables = QListWidget()
        
        subLayouts['LeftColumn'].addWidget(self.variables, 7,0,4,1)
        subLayouts['LeftColumn'].addWidget(self.selectedVariables, 7,1,4,1)
        subLayouts['LeftColumn'].addWidget(self.buttons['addVariable'], 10,0,1,1)
        subLayouts['LeftColumn'].addWidget(self.buttons['removeVariable'], 10,1,1,1)
        subLayouts['LeftColumn'].addWidget(self.buttons['Toolkit'], 11,1,1,1)
        
        names = ['apple', 'banana', 'Cherry']
        self.variables.insertItems(0, names)
        
    def setButtonConnections(self):
        self.buttons['addVariable'].clicked.connect(self.add_variable)
        self.buttons['Toolkit'].clicked.connect(self.show_new_window)   
        self.buttons['Toolkit'].clicked.connect(self.add_selected_variables)
        
    def add_variable(self):
        for item in self.variables.selectedItems():
            self.selectedVariables.addItem(item.clone())

    def show_new_window(self):
        self.sw.show()
        
    def add_selected_variables(self):
        items = []
        for i in range(self.selectedVariables.count()):
            items.append(self.selectedVariables.item(i).clone())
        self.tw.setItems(items)


if __name__ == "__main__":
    import sys
    app = QApplication([])
    mw = MainWindow()
    mw.show()
    app.exec()