设置了两个 Frame ,一个为左边内部组件为垂直布局的按钮集合,一个为右边用于 页面切换 的方形区域,宽度比为 1 : 5

初始化 stackedWidget

# 以父 Frame 为父组件,构建完整覆盖父 Frame 的空间
self.stackedWidget = QtWidgets.QStackedWidget(self.frame_2)
self.stackedWidget.setGeometry(QtCore.QRect(0, 0, 651, 551))
self.stackedWidget.setObjectName("stackedWidget")

成员加入 stackedWidget

# 声明一个页面
self.page = QtWidgets.QWidget()
self.page.setObjectName("page")
# 通过方法配置 Tab ,类似于 Page
self.setTabs_Page_1_Frame_2()
# 将该页面加入 stackedWidget
self.stackedWidget.addWidget(self.page)
# 声明第 2 个页面
self.page_2 = QtWidgets.QWidget()
self.page_2.setObjectName("page_2")
......
# 将该页面加入 stackedWidget
self.stackedWidget.addWidget(self.page_2)
# 声明第 3 个页面
self.page_3 = QtWidgets.QWidget()
self.page_3.setObjectName("page_3")
......
# 将该页面加入 stackedWidget
self.stackedWidget.addWidget(self.page_3)

切换调用 stackedWidget

要将 Frame 2 页面内容切换,需要指定 stackedWidget 的索引,第一个添加的页面对应索引为 0

self.stackedWidget.setCurrentIndex(0)

按钮调用 stackedWidget

Frame 1 中声明了三个 PushButton ,通过 clicked 点击触发切换函数。

因为自定义槽函数需要使用到 lambda 匿名函数,请参考 PyQt5 信号、槽函数和 lambda 匿名函数

self.pushButton.clicked.connect(lambda: self.printStr("123"))
# -*- coding: utf-8 -*-
# Form implementation generated from reading ui file 'untitled.ui'
# Created by: PyQt5 UI code generator 5.15.7
# WARNING: Any manual changes made to this file will be lost when pyuic5 is
# run again.  Do not edit this file unless you know what you are doing.
import sys
from PyQt5 import QtCore, QtGui, QtWidgets
class Ui_MainWindow(object):
    def __init__(self):
        self.centralwidget = None
        self.menubar = None
        self.layoutWidget = None
        self.horizontalLayout = None
        self.widget = None
        self.verticalLayout = None
        self.fileMenu = None
        self.fileMenuAction = None
        self.fileMenuAction_2 = None
        self.fileMenuAction_3 = None
        self.pushButton = None
        self.pushButton_2 = None
        self.pushButton_3 = None
        self.frame = None
        self.frame_2 = None
        self.stackedWidget = None
        self.tabWidget = None
        self.tab = None
        self.tab_2 = None
        self.page = None
        self.page_2 = None
        self.page_3 = None
        self.label = None
        self.label_2 = None
        self.label_3 = None
        self.label_4 = None
        self.action = None
        self.action_2 = None
        self.action_3 = None
    def setupUi(self, MainWindow):
        MainWindow.setObjectName("MainWindow")
        MainWindow.resize(800, 600)
        self.centralwidget = QtWidgets.QWidget(MainWindow)
        self.centralwidget.setObjectName("centralwidget")
        self.layoutWidget = QtWidgets.QWidget(self.centralwidget)
        self.layoutWidget.setGeometry(QtCore.QRect(0, 0, 791, 551))
        self.layoutWidget.setObjectName("layoutWidget")
        self.horizontalLayout = QtWidgets.QHBoxLayout(self.layoutWidget)
        self.horizontalLayout.setContentsMargins(0, 0, 0, 0)
        self.horizontalLayout.setObjectName("horizontalLayout")
        self.setMenu(MainWindow)
        self.setFrame_1()
        self.setFrame_2()
        MainWindow.setCentralWidget(self.centralwidget)
        self.setActions(MainWindow)
        self.retranslateUi(MainWindow)
        self.stackedWidget.setCurrentIndex(0)
        self.tabWidget.setCurrentIndex(0)
        QtCore.QMetaObject.connectSlotsByName(MainWindow)
    def retranslateUi(self, MainWindow):
        _translate = QtCore.QCoreApplication.translate
        MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
        self.pushButton.setText(_translate("MainWindow", "页面1"))
        self.pushButton_2.setText(_translate("MainWindow", "页面2"))
        self.pushButton_3.setText(_translate("MainWindow", "页面3"))
        # Page 1
        self.label.setText(_translate("MainWindow", "TextLabel 1"))
        self.tabWidget.setTabText(self.tabWidget.indexOf(self.tab), _translate("MainWindow", "Tab 1"))
        self.label_2.setText(_translate("MainWindow", "TextLabel 2"))
        self.tabWidget.setTabText(self.tabWidget.indexOf(self.tab_2), _translate("MainWindow", "Tab 2"))
        # Page 2
        self.label_3.setText(_translate("MainWindow", "Page 2"))
        # Page 3
        self.label_4.setText(_translate("MainWindow", "Page 3"))
        # Actions
        self.action.setText(_translate("MainWindow", "action"))
        self.action_2.setText(_translate("MainWindow", "action_2"))
        self.action_3.setText(_translate("MainWindow", "action_3"))
    def setActions(self, MainWindow):
        self.action = QtWidgets.QAction(MainWindow)
        self.action.setObjectName("action")
        self.action_2 = QtWidgets.QAction(MainWindow)
        self.action_2.setObjectName("action_2")
        self.action_3 = QtWidgets.QAction(MainWindow)
        self.action_3.setObjectName("action_3")
    def setFrame_1(self):
        主界面左侧 3 个按钮定为 1 个 Frame ,内部组件采用垂直布局
        :return:
        self.frame = QtWidgets.QFrame(self.layoutWidget)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Expanding)
        sizePolicy.setHorizontalStretch(1)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.frame.sizePolicy().hasHeightForWidth())
        self.frame.setSizePolicy(sizePolicy)
        self.frame.setFrameShape(QtWidgets.QFrame.StyledPanel)
        self.frame.setFrameShadow(QtWidgets.QFrame.Raised)
        self.frame.setObjectName("frame")
        self.widget = QtWidgets.QWidget(self.frame)
        self.widget.setGeometry(QtCore.QRect(0, 0, 131, 551))
        self.widget.setObjectName("widget")
        self.verticalLayout = QtWidgets.QVBoxLayout(self.widget)
        self.verticalLayout.setContentsMargins(0, 0, 0, 0)
        self.verticalLayout.setObjectName("verticalLayout")
        self.setPushButton_Frame_1()
        self.horizontalLayout.addWidget(self.frame)
    def setPushButton_Frame_1(self):
        对 Frame 1 的按钮进行声明 和 点击触发方法 配置
        :return:
        self.pushButton = QtWidgets.QPushButton(self.widget)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Expanding)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.pushButton.sizePolicy().hasHeightForWidth())
        self.pushButton.setSizePolicy(sizePolicy)
        self.pushButton.setObjectName("pushButton")
        # 加入垂直布局列表
        self.verticalLayout.addWidget(self.pushButton)
        self.pushButton_2 = QtWidgets.QPushButton(self.widget)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Expanding)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.pushButton_2.sizePolicy().hasHeightForWidth())
        self.pushButton_2.setSizePolicy(sizePolicy)
        self.pushButton_2.setObjectName("pushButton_2")
        self.verticalLayout.addWidget(self.pushButton_2)
        self.pushButton_3 = QtWidgets.QPushButton(self.widget)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Expanding)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.pushButton_3.sizePolicy().hasHeightForWidth())
        self.pushButton_3.setSizePolicy(sizePolicy)
        self.pushButton_3.setObjectName("pushButton_3")
        self.verticalLayout.addWidget(self.pushButton_3)
        # 点击触发方法
        # self.pushButton.clicked.connect(self.gotoStack_1)
        self.pushButton.clicked.connect(lambda: self.gotoStack(0))
        self.pushButton_2.clicked.connect(lambda: self.gotoStack(1))
        self.pushButton_3.clicked.connect(lambda: self.gotoStack(2))
    def setFrame_2(self):
        self.frame_2 = QtWidgets.QFrame(self.layoutWidget)
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Expanding)
        sizePolicy.setHorizontalStretch(5)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.frame_2.sizePolicy().hasHeightForWidth())
        self.frame_2.setSizePolicy(sizePolicy)
        self.frame_2.setFrameShape(QtWidgets.QFrame.StyledPanel)
        self.frame_2.setFrameShadow(QtWidgets.QFrame.Raised)
        self.frame_2.setObjectName("frame_2")
        self.stackedWidget = QtWidgets.QStackedWidget(self.frame_2)
        self.stackedWidget.setGeometry(QtCore.QRect(0, 0, 651, 551))
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Expanding, QtWidgets.QSizePolicy.Expanding)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.stackedWidget.sizePolicy().hasHeightForWidth())
        self.stackedWidget.setSizePolicy(sizePolicy)
        self.stackedWidget.setObjectName("stackedWidget")
        self.setPages_Frame_2()
        self.horizontalLayout.addWidget(self.frame_2)
    def setPages_Frame_2(self):
        self.page = QtWidgets.QWidget()
        self.page.setObjectName("page")
        self.setTabs_Page_1_Frame_2()
        self.stackedWidget.addWidget(self.page)
        self.page_2 = QtWidgets.QWidget()
        self.page_2.setObjectName("page_2")
        self.label_3 = QtWidgets.QLabel(self.page_2)
        self.label_3.setGeometry(QtCore.QRect(180, 230, 281, 111))
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Preferred, QtWidgets.QSizePolicy.Preferred)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.label_3.sizePolicy().hasHeightForWidth())
        self.label_3.setSizePolicy(sizePolicy)
        font = QtGui.QFont()
        font.setFamily("Arial")
        font.setPointSize(28)
        self.label_3.setFont(font)
        self.label_3.setLayoutDirection(QtCore.Qt.LeftToRight)
        self.label_3.setAlignment(QtCore.Qt.AlignCenter)
        self.label_3.setObjectName("label_3")
        self.stackedWidget.addWidget(self.page_2)
        self.page_3 = QtWidgets.QWidget()
        self.page_3.setObjectName("page_3")
        self.label_4 = QtWidgets.QLabel(self.page_3)
        self.label_4.setGeometry(QtCore.QRect(190, 240, 281, 111))
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Preferred, QtWidgets.QSizePolicy.Preferred)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.label_4.sizePolicy().hasHeightForWidth())
        self.label_4.setSizePolicy(sizePolicy)
        font = QtGui.QFont()
        font.setFamily("Arial")
        font.setPointSize(28)
        self.label_4.setFont(font)
        self.label_4.setLayoutDirection(QtCore.Qt.LeftToRight)
        self.label_4.setAlignment(QtCore.Qt.AlignCenter)
        self.label_4.setObjectName("label_4")
        self.stackedWidget.addWidget(self.page_3)
    def setTabs_Page_1_Frame_2(self):
        self.tabWidget = QtWidgets.QTabWidget(self.page)
        self.tabWidget.setGeometry(QtCore.QRect(-10, 0, 661, 551))
        self.tabWidget.setObjectName("tabWidget")
        self.tab = QtWidgets.QWidget()
        self.tab.setObjectName("tab")
        self.label = QtWidgets.QLabel(self.tab)
        self.label.setGeometry(QtCore.QRect(180, 200, 281, 111))
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Preferred, QtWidgets.QSizePolicy.Preferred)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.label.sizePolicy().hasHeightForWidth())
        self.label.setSizePolicy(sizePolicy)
        font = QtGui.QFont()
        font.setFamily("Arial")
        font.setPointSize(28)
        self.label.setFont(font)
        self.label.setLayoutDirection(QtCore.Qt.LeftToRight)
        self.label.setAlignment(QtCore.Qt.AlignCenter)
        self.label.setObjectName("label")
        self.tabWidget.addTab(self.tab, "")
        self.tab_2 = QtWidgets.QWidget()
        self.tab_2.setObjectName("tab_2")
        self.label_2 = QtWidgets.QLabel(self.tab_2)
        self.label_2.setGeometry(QtCore.QRect(190, 210, 281, 111))
        sizePolicy = QtWidgets.QSizePolicy(QtWidgets.QSizePolicy.Preferred, QtWidgets.QSizePolicy.Preferred)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.label_2.sizePolicy().hasHeightForWidth())
        self.label_2.setSizePolicy(sizePolicy)
        font = QtGui.QFont()
        font.setFamily("Arial")
        font.setPointSize(28)
        self.label_2.setFont(font)
        self.label_2.setLayoutDirection(QtCore.Qt.LeftToRight)
        self.label_2.setAlignment(QtCore.Qt.AlignCenter)
        self.label_2.setObjectName("label_2")
        self.tabWidget.addTab(self.tab_2, "")
    def gotoStack(self, index: int):
        Frame 2 的第 index 个界面, index = 0
        :param index: 
        :return: 
        self.stackedWidget.setCurrentIndex(index)
    def setMenu(self, MainWindow):
                配置菜单栏
                :return:
        # 声明菜单栏
        self.menubar = QtWidgets.QMenuBar(self.ui)
        self.menubar = QtWidgets.QMenuBar()
        self.ui.setMenuBar(self.menubar)
        self.menubar = QtWidgets.QMenuBar()
        self.menubar.setGeometry(QtCore.QRect(0, 0, 800, 23))
        self.menubar.setObjectName("menubar")
        # 添加菜单组件
        self.fileMenu = QtWidgets.QMenu(self.menubar)
        self.fileMenu.setObjectName("fileMenu")
        self.fileMenu.setTitle("文件")
        # 添加单一组件
        self.fileMenuAction = QtWidgets.QAction("Page 1")
        self.fileMenuAction.triggered.connect(self.gotoStack_1)
        self.fileMenuAction_2 = QtWidgets.QAction("Page 2")
        self.fileMenuAction_2.triggered.connect(self.gotoStack_2)
        self.fileMenuAction_3 = QtWidgets.QAction("Page 3")
        self.fileMenuAction_3.triggered.connect(self.gotoStack_3)
        # 构建文件菜单
        self.fileMenu.addAction(self.fileMenuAction)
        self.fileMenu.addSeparator()
        self.fileMenu.addAction(self.fileMenuAction_2)
        self.fileMenu.addSeparator()
        self.fileMenu.addAction(self.fileMenuAction_3)
        # 构建菜单栏
        self.menubar.addAction(self.fileMenu.menuAction())
        MainWindow.setMenuBar(self.menubar)
if __name__ == "__main__":
    # 创建活跃 app 句柄
    app = QtWidgets.QApplication(sys.argv)
    # 关闭全部窗口后程序不退出
    app.setQuitOnLastWindowClosed(False)
    # 声明界面句柄
    mainWindow = QtWidgets.QMainWindow()
    # 构建程序界面
    ui = Ui_MainWindow()
    ui.setupUi(mainWindow)
    # 程序启动时打开主界面
    mainWindow.show()
    sys.exit(app.exec_())