如何从子窗口获取小部件值到另一个窗口

试试这样：

主文件

import sys
import platform
'''
from PySide2 import QtCore, QtGui, QtWidgets
from PySide2.QtCore import (QCoreApplication, QPropertyAnimation, QDate, QDateTime, QMetaObject, QObject, QPoint, QRect, QSize, QTime, QUrl, Qt, QEvent)
from PySide2.QtGui import (QBrush, QColor, QConicalGradient, QCursor, QFont, QFontDatabase, QIcon, QKeySequence, QLinearGradient, QPalette, QPainter, QPixmap, QRadialGradient)
from PySide2.QtWidgets import *
'''
from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.Qt import *

# ||| my imports
import asyncio
# from asyncqt import QEventLoop, asyncSlot  # для асинхронности pyqt5
# ? from loguru import logger                # библиотека для вывода сообщений/логов

# GUI FILE
from q1429928_ui_main import Ui_MainWindow

# IMPORT FUNCTIONS
from q1429928_ui_functions import UiFunctions                      # !!! 


class MainWindow(QMainWindow):
    """ Главное окно программы
    работа с таблицами из БД по "Шасси" """
    
    def __init__(self, parent=None):
#        QMainWindow.__init__(self)
        super(MainWindow, self).__init__(parent)                   # !!!

        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)

# !!! +++
        self.windowLogon = parent                                  # !!! +++
        self.uiFunctions = UiFunctions(self.windowLogon, self)     # !!! +++

        ## TOGGLE/BURGUER MENU
        self.ui.Btn_Toggle.clicked.connect(
#            lambda: UIFunctions.toggleMenu(self, 250, True))
            lambda: self.uiFunctions.toggleMenu(250, True))        # !!! +++
            
        # PAGE 1
        self.ui.btn_page_1.clicked.connect(lambda: self.ui.stackedWidget.setCurrentWidget(self.ui.page_1))
        self.ui.show_content.clicked.connect(
#            lambda: UIFunctions.sql_content(self))  
            self.uiFunctions.sql_content)                          # !!! +++
            
        # PAGE 2
        self.ui.btn_page_2.clicked.connect(lambda: self.ui.stackedWidget.setCurrentWidget(self.ui.page_2))

        # PAGE 3
        self.ui.btn_page_3.clicked.connect(lambda: self.ui.stackedWidget.setCurrentWidget(self.ui.page_3))

#        self.ui.pushButton.clicked.connect(lambda: self.show_logon_window())
        self.ui.pushButton.clicked.connect(self.show_logon_window)            # !!!
        
#        ## SHOW ==> MAIN WINDOW
#        self.show()
#        ## ==> END ##

    def show_logon_window(self):
#        self.w = Logon()
#        self.w.show()
# !!! +++
        self.windowLogon.setGeometry(600, 300, 200, 150)              # !!! +++        
        self.windowLogon.show()                                       # !!! +++
        self.hide()                                                   #


class Logon(QWidget):
    """ Класс окно - авторизации
    """
    def __init__(self, parent=None):
        super(Logon, self).__init__(parent)
        self.parent = parent        # поставил для реализации дочернего окна
        self.resize(200, 150)
        
        self.button = QPushButton("Войти")
        self.button.clicked.connect(self.show_main_window)
        self.label = QLabel("Введите логин и пароль для входа")
        self.login_edit = QLineEdit('логин')          # вот значение ко-е надо получить в основном окне
        self.password_edit = QLineEdit('пароль')
        self.password_edit.setEchoMode(QLineEdit.Password)    

        layout = QVBoxLayout()
        layout.addWidget(self.label)
        layout.addWidget(self.login_edit)
        layout.addWidget(self.password_edit)
        layout.addWidget(self.button)
        self.setLayout(layout)

    def show_main_window(self):
        """ при входе в систему откроется главное окно программмы 
        для работы с БД и тд , и скрывая само окно авторизации
        :return:
        """
        # x = self.login_edit.text()
        # logger.info(f"your login is: {x}")

# ----> vvvv   !!! +++  --> vvvv
        self.w = MainWindow(self)                                # !!! +++ self
        self.w.setGeometry(200, 150, 1000, 500)                  # !!! +++
        self.w.show()                          # show window main
        self.hide()                            # hide window of authorization


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

    app.setStyle("Fusion")
    palette = QPalette()
    palette.setColor(QPalette.Window, QColor(53, 53, 53))
    palette.setColor(QPalette.WindowText, Qt.white)
    palette.setColor(QPalette.Base, QColor(25, 25, 25))
    palette.setColor(QPalette.AlternateBase, QColor(53, 53, 53))
    palette.setColor(QPalette.ToolTipBase, Qt.white)
    palette.setColor(QPalette.ToolTipText, Qt.white)
    palette.setColor(QPalette.Text, Qt.white)
    palette.setColor(QPalette.Button, QColor(45, 53, 53))
    palette.setColor(QPalette.ButtonText, Qt.white)
    palette.setColor(QPalette.BrightText, Qt.red)
    palette.setColor(QPalette.Link, QColor(12, 100, 238))
    palette.setColor(QPalette.Highlight, QColor(182, 115, 228))
    palette.setColor(QPalette.HighlightedText, Qt.black)
    app.setPalette(palette)
    app.setStyleSheet(
        "QToolTip { color: #ffffff; background-color: #2a82da; border: 1px solid white; }"
    )

    ex = Logon()
    ex.show()    
    sys.exit(app.exec_())

q1429928_ui_main.py

'''
from PySide2.QtCore import (QCoreApplication, QMetaObject, QObject, QPoint,
    QRect, QSize, QUrl, Qt)
from PySide2.QtGui import (QBrush, QColor, QConicalGradient, QCursor, QFont,
    QFontDatabase, QIcon, QLinearGradient, QPalette, QPainter, QPixmap,
    QRadialGradient)
from PySide2.QtWidgets import *
'''
from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.Qt import *


class Ui_MainWindow(object):
    def setupUi(self, MainWindow):
        if MainWindow.objectName():
            MainWindow.setObjectName(u"MainWindow")
        MainWindow.resize(1000, 500)
        MainWindow.setMinimumSize(QSize(1000, 500))
        MainWindow.setStyleSheet(u"background-color: rgb(45, 45, 45);")
        self.centralwidget = QWidget(MainWindow)
        self.centralwidget.setObjectName(u"centralwidget")
        self.verticalLayout = QVBoxLayout(self.centralwidget)
        self.verticalLayout.setSpacing(0)
        self.verticalLayout.setObjectName(u"verticalLayout")
        self.verticalLayout.setContentsMargins(0, 0, 0, 0)
        self.Top_Bar = QFrame(self.centralwidget)
        self.Top_Bar.setObjectName(u"Top_Bar")
        self.Top_Bar.setMaximumSize(QSize(16777215, 40))
        self.Top_Bar.setStyleSheet(u"background-color: rgb(35, 35, 35);")
        self.Top_Bar.setFrameShape(QFrame.NoFrame)
        self.Top_Bar.setFrameShadow(QFrame.Raised)
        self.horizontalLayout = QHBoxLayout(self.Top_Bar)
        self.horizontalLayout.setSpacing(0)
        self.horizontalLayout.setObjectName(u"horizontalLayout")
        self.horizontalLayout.setContentsMargins(0, 0, 0, 0)
        self.frame_toggle = QFrame(self.Top_Bar)
        self.frame_toggle.setObjectName(u"frame_toggle")
        self.frame_toggle.setMaximumSize(QSize(70, 40))
        self.frame_toggle.setStyleSheet(u"background-color: rgb(85, 170, 255);")
        self.frame_toggle.setFrameShape(QFrame.StyledPanel)
        self.frame_toggle.setFrameShadow(QFrame.Raised)
        self.verticalLayout_2 = QVBoxLayout(self.frame_toggle)
        self.verticalLayout_2.setSpacing(0)
        self.verticalLayout_2.setObjectName(u"verticalLayout_2")
        self.verticalLayout_2.setContentsMargins(0, 0, 0, 0)
        self.Btn_Toggle = QPushButton(self.frame_toggle)
        self.Btn_Toggle.setObjectName(u"Btn_Toggle")
        sizePolicy = QSizePolicy(QSizePolicy.Expanding, QSizePolicy.Expanding)
        sizePolicy.setHorizontalStretch(0)
        sizePolicy.setVerticalStretch(0)
        sizePolicy.setHeightForWidth(self.Btn_Toggle.sizePolicy().hasHeightForWidth())
        self.Btn_Toggle.setSizePolicy(sizePolicy)
        self.Btn_Toggle.setStyleSheet(u"color: rgb(255, 255, 255);\n"
"border: 0px solid;")

        self.verticalLayout_2.addWidget(self.Btn_Toggle)

        self.horizontalLayout.addWidget(self.frame_toggle)

        self.frame_top = QFrame(self.Top_Bar)
        self.frame_top.setObjectName(u"frame_top")
        self.frame_top.setFrameShape(QFrame.StyledPanel)
        self.frame_top.setFrameShadow(QFrame.Raised)
        self.pushButton = QPushButton(self.frame_top)
        self.pushButton.setObjectName(u"pushButton")
        self.pushButton.setGeometry(QRect(700, 2, 231, 31))
        self.pushButton.setStyleSheet(u"color: rgb(255, 246, 248);\n"
"font: 12pt \"MS Shell Dlg 2\";")

        # Welcome label
        self.welcome_label = QLabel(self.frame_top)
        self.welcome_label.setGeometry(QRect(65, 2, 170, 31))
        self.welcome_label.setText('welcome user:')

        self.horizontalLayout.addWidget(self.frame_top)


        self.verticalLayout.addWidget(self.Top_Bar)

        self.Content = QFrame(self.centralwidget)
        self.Content.setObjectName(u"Content")
        self.Content.setFrameShape(QFrame.NoFrame)
        self.Content.setFrameShadow(QFrame.Raised)
        self.horizontalLayout_2 = QHBoxLayout(self.Content)
        self.horizontalLayout_2.setSpacing(0)
        self.horizontalLayout_2.setObjectName(u"horizontalLayout_2")
        self.horizontalLayout_2.setContentsMargins(0, 0, 0, 0)
        self.frame_left_menu = QFrame(self.Content)
        self.frame_left_menu.setObjectName(u"frame_left_menu")
        self.frame_left_menu.setMinimumSize(QSize(120, 0))      # установка ширины левого frame
        self.frame_left_menu.setMaximumSize(QSize(70, 16777215))
        self.frame_left_menu.setStyleSheet(u"background-color: rgb(35, 35, 35);")
        self.frame_left_menu.setFrameShape(QFrame.StyledPanel)
        self.frame_left_menu.setFrameShadow(QFrame.Raised)
        self.verticalLayout_3 = QVBoxLayout(self.frame_left_menu)
        self.verticalLayout_3.setObjectName(u"verticalLayout_3")
        self.verticalLayout_3.setContentsMargins(0, 0, 0, 0)
        self.frame_top_menus = QFrame(self.frame_left_menu)
        self.frame_top_menus.setObjectName(u"frame_top_menus")
        self.frame_top_menus.setFrameShape(QFrame.NoFrame)
        self.frame_top_menus.setFrameShadow(QFrame.Raised)
        self.verticalLayout_4 = QVBoxLayout(self.frame_top_menus)
        self.verticalLayout_4.setSpacing(0)
        self.verticalLayout_4.setObjectName(u"verticalLayout_4")
        self.verticalLayout_4.setContentsMargins(0, 0, 0, 0)
        self.btn_page_1 = QPushButton(self.frame_top_menus)
        self.btn_page_1.setObjectName(u"btn_page_1")
        self.btn_page_1.setMinimumSize(QSize(0, 40))
        self.btn_page_1.setStyleSheet(u"QPushButton {\n"
"   color: rgb(255, 255, 255);\n"
"   background-color: rgb(35, 35, 35);\n"
"   border: 0px solid;\n"
"}\n"
"QPushButton:hover {\n"
"   background-color: rgb(85, 170, 255);\n"
"}")

        self.verticalLayout_4.addWidget(self.btn_page_1)

        self.btn_page_2 = QPushButton(self.frame_top_menus)
        self.btn_page_2.setObjectName(u"btn_page_2")
        self.btn_page_2.setMinimumSize(QSize(0, 40))
        self.btn_page_2.setStyleSheet(u"QPushButton {\n"
"   color: rgb(255, 255, 255);\n"
"   background-color: rgb(35, 35, 35);\n"
"   border: 0px solid;\n"
"}\n"
"QPushButton:hover {\n"
"   background-color: rgb(85, 170, 255);\n"
"}")

        self.verticalLayout_4.addWidget(self.btn_page_2)

        self.btn_page_3 = QPushButton(self.frame_top_menus)
        self.btn_page_3.setObjectName(u"btn_page_3")
        self.btn_page_3.setMinimumSize(QSize(0, 40))
        self.btn_page_3.setStyleSheet(u"QPushButton {\n"
"   color: rgb(255, 255, 255);\n"
"   background-color: rgb(35, 35, 35);\n"
"   border: 0px solid;\n"
"}\n"
"QPushButton:hover {\n"
"   background-color: rgb(85, 170, 255);\n"
"}")

        self.verticalLayout_4.addWidget(self.btn_page_3)

        # ||| Tree ||| ---------------------------------------------------- >
        self.tree = QTreeWidget(self.frame_top_menus)
        # Установить количество столбцов
        self.tree.setColumnCount(1)
        self.tree.setMinimumSize(QSize(0, 80))
        # self.tree.setColumnWidth(0, 100)

        root = QTreeWidgetItem(self.tree)
        root.setText(0, 'Отчеты')

        root_2 = QTreeWidgetItem(self.tree)
        root_2.setText(0, 'Справочники \nи опции')

        # Установить дочерний узел 1
        child1 = QTreeWidgetItem()
        child1.setText(0, 'Отчет за месяц')
        root.addChild(child1)

        # Установить дочерний узел 2
        child2 = QTreeWidgetItem()
        child2.setText(0, 'Отчет за сутки')
        root.addChild(child2)

        # Установить дочерний узел 3
        child3 = QTreeWidgetItem()
        child3.setText(0, 'Сводка по дням')
        root.addChild(child3)

        # Установить дочерний узел 4
        child4 = QTreeWidgetItem()
        child4.setText(0, 'Сводка по шасси')
        root.addChild(child4)

        # Установить дочерний узел 5
        child5 = QTreeWidgetItem()
        child5.setText(0, 'Сводка по сдаче АВЗ')
        root.addChild(child5)

        ## -- Второй подраздел ------------------------
        # Установить дочерний узел 1
        child2_1 = QTreeWidgetItem()
        child2_1.setText(0, 'Справочник цветов')
        root_2.addChild(child2_1)

        # Установить дочерний узел 2
        child2_2 = QTreeWidgetItem()
        child2_2.setText(0, 'Справочник обьемов')
        root_2.addChild(child2_2)

        # Установить дочерний узел 3
        child3_3 = QTreeWidgetItem()
        child3_3.setText(0, 'Справочник спецтехники')
        root_2.addChild(child3_3)

        # Установить дочерний узел 4
        child4_4 = QTreeWidgetItem()
        child4_4.setText(0, 'Справочник сидений')
        root_2.addChild(child4_4)

        # Установить дочерний узел 5
        child5_5 = QTreeWidgetItem()
        child5_5.setText(0, 'Справочник мест')
        root_2.addChild(child5_5)

        # Установить дочерний узел 6
        child6_6 = QTreeWidgetItem()
        child6_6.setText(0, 'Справочник модификаций')
        root_2.addChild(child6_6)

        self.verticalLayout_4.addWidget(self.tree)    # add  tree to Layout
        self.verticalLayout_3.addWidget(self.frame_top_menus, 0, Qt.AlignTop)
        self.horizontalLayout_2.addWidget(self.frame_left_menu)

        self.frame_pages = QFrame(self.Content)
        self.frame_pages.setObjectName(u"frame_pages")
        self.frame_pages.setFrameShape(QFrame.StyledPanel)
        self.frame_pages.setFrameShadow(QFrame.Raised)
        self.verticalLayout_5 = QVBoxLayout(self.frame_pages)
        self.verticalLayout_5.setObjectName(u"verticalLayout_5")
        self.stackedWidget = QStackedWidget(self.frame_pages)
        self.stackedWidget.setObjectName(u"stackedWidget")
        self.page_1 = QWidget()
        self.page_1.setObjectName(u"page_1")
        self.verticalLayout_7 = QVBoxLayout(self.page_1)
        self.verticalLayout_7.setObjectName(u"verticalLayout_7")
        # self.test = Qta
        self.label_1 = QLabel(self.page_1)
        self.label_1.setObjectName(u"label_1")
        font = QFont()
        font.setPointSize(40)
        self.label_1.setFont(font)
        self.label_1.setStyleSheet(u"color: #FFF;")
        self.label_1.setAlignment(Qt.AlignRight)

        self.verticalLayout_7.addWidget(self.label_1)

        # Table widget ---------------------------- >
        self.table = QTableWidget(self.page_1)    # Create a table
        # self.table.setColumnCount(3)            # кол-во столбцов

        self.show_content = QPushButton(self.page_1)  # button press show content in table

        # self.label_2 = QLabel(self.page_1)
        # self.label_2.setObjectName(u"label_2")
        # self.label_2.setGeometry(QRect(1, 5, 121, 61))
        # self.label_2.setStyleSheet(u"font: 20pt \"MS Shell Dlg 2\";\n"
        #                            "font: 12pt \"MS Shell Dlg 2\";")
        # self.label_2.setText(u"Введите год: \nВведите месяц:")
        # self.label_2.setText(u"введите месяц !!!")
        self.comboBox = QComboBox(self.page_1)
        self.comboBox.setObjectName(u"comboBox")
        self.comboBox.setGeometry(QRect(350, 2, 69, 22))
        self.comboBox.setMaximumWidth(100)
        year_list = ['Выберите год', 2020, 2021, 2022]
        month_list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
        new_list = list(map(lambda x: self.comboBox.addItem(str(x)), year_list))

        self.comboBox_2 = QComboBox(self.page_1)
        self.comboBox_2.setObjectName(u"comboBox_2")
        self.comboBox_2.setGeometry(QRect(350, 6, 69, 22))
        self.comboBox_2.setMaximumWidth(100)
        new_list_2 = list(map(lambda y: self.comboBox_2.addItem(str(y)), month_list))

        self.show_content.setMinimumSize(150, 40)
        self.show_content.setMaximumSize(150, 40)

        self.table.resizeColumnsToContents()
        self.verticalLayout_7.addWidget(self.comboBox)  # change year of Combobox
        self.verticalLayout_7.addWidget(self.comboBox_2)  # change year of Combobox

        self.verticalLayout_7.addWidget(self.show_content)  # add press button widget to page_1
        self.verticalLayout_7.addWidget(self.table)   # add table widget to page_1

        # -------------------------------------------------------

        self.stackedWidget.addWidget(self.page_1)
        self.page_2 = QWidget()
        self.page_2.setObjectName(u"page_2")
        self.verticalLayout_6 = QVBoxLayout(self.page_2)
        self.verticalLayout_6.setObjectName(u"verticalLayout_6")
        self.label_2 = QLabel(self.page_2)
        self.label_2.setObjectName(u"label_2")
        self.label_2.setFont(font)
        self.label_2.setStyleSheet(u"color: #FFF;")
        self.label_2.setAlignment(Qt.AlignCenter)

        self.verticalLayout_6.addWidget(self.label_2)

        self.stackedWidget.addWidget(self.page_2)
        self.page_3 = QWidget()
        self.page_3.setObjectName(u"page_3")
        self.verticalLayout_8 = QVBoxLayout(self.page_3)
        self.verticalLayout_8.setObjectName(u"verticalLayout_8")
        self.label = QLabel(self.page_3)
        self.label.setObjectName(u"label")
        self.label.setFont(font)
        self.label.setStyleSheet(u"color: #FFF;")
        self.label.setAlignment(Qt.AlignCenter)

        self.verticalLayout_8.addWidget(self.label)
        self.stackedWidget.addWidget(self.page_3)

        self.verticalLayout_5.addWidget(self.stackedWidget)
        self.horizontalLayout_2.addWidget(self.frame_pages)
        self.verticalLayout.addWidget(self.Content)

        MainWindow.setCentralWidget(self.centralwidget)
        self.retranslateUi(MainWindow)
        self.stackedWidget.setCurrentIndex(0)

        QMetaObject.connectSlotsByName(MainWindow)

    def retranslateUi(self, MainWindow):
        MainWindow.setWindowTitle(QCoreApplication.translate("MainWindow", u"MainWindow", None))
        self.Btn_Toggle.setText(QCoreApplication.translate("MainWindow", u"Развернуть", None))
        self.pushButton.setText(QCoreApplication.translate("MainWindow", u"\u0412\u0435\u0440\u043d\u0443\u0442\u044c\u0441\u044f \u0432 \u043e\u043a\u043d\u043e \u0430\u0432\u0442\u043e\u0440\u0438\u0437\u0430\u0446\u0438\u0438", None))
        self.btn_page_1.setText(QCoreApplication.translate("MainWindow", u"Журнал\n изменений", None))
        self.btn_page_2.setText(QCoreApplication.translate("MainWindow", u"Page 2", None))
        self.btn_page_3.setText(QCoreApplication.translate("MainWindow", u"Page 3", None))
        self.label_1.setText(QCoreApplication.translate("MainWindow", u"PAGE 1", None))
        self.label_2.setText(QCoreApplication.translate("MainWindow", u"PAGE 2", None))
        self.label.setText(QCoreApplication.translate("MainWindow", u"PAGE 3", None))
        self.show_content.setText(QCoreApplication.translate("MainWindow", u"Показать данные", None))

q1429928_ui_functions.py

import os
# ? from loguru import logger     

## ==> GUI FILE
# ? from main import MainWindow, QPropertyAnimation, QtCore, QTableWidgetItem
# ? from main import Logon  # класс реализации окна авторизации !!!

from PyQt5 import QtCore, QtGui, QtWidgets                          # +++
from PyQt5.Qt import *                                              # +++

# ??? os.system('cls')


#class UIFunctions(MainWindow):
class UiFunctions(QMainWindow):                                     # +++
    def __init__(self, windowLogon, parent=None):                   # +++
        super(UiFunctions, self).__init__(parent)                   # +++
# +++        
        self.parent = parent                                        # +++
        self.windowLogon = windowLogon                              # +++

    def toggleMenu(self, maxWidth, enable):
        if enable:

            # GET WIDTH
#            width = self.ui.frame_left_menu.width()
            width = self.parent.ui.frame_left_menu.width()          # +++

            maxExtend = maxWidth
            standard = 70

            # SET MAX WIDTH
            if width == 70:
                # self.ui.Btn_Toggle.setText('Развернуть')
                widthExtended = maxExtend
            else:
                # print("test")
                # self.ui.Btn_Toggle.setText('Свернуть')
                widthExtended = standard

            # ANIMATION
#            self.animation = QPropertyAnimation(self.ui.frame_left_menu, b"minimumWidth")

            self.animation = QPropertyAnimation(
                self.parent.ui.frame_left_menu, b"minimumWidth")             # +++
            
            self.animation.setDuration(400)
            self.animation.setStartValue(width)
            self.animation.setEndValue(widthExtended)
            self.animation.setEasingCurve(QtCore.QEasingCurve.InOutQuart)
            self.animation.start()

    def sql_content(self):
        """ вывод данных 
        и попытка получить значение из другого окна (авторизация)
        """
        
        # test check value from child window
#        test_a = self.login_edit.text()       # пробую получить значения из окна авторизации ???
        # test_b = self.Logon.login_edit()     # другая попытка
        
        
        test_a = self.windowLogon.login_edit.text()                    # +++
        print(f'def sql_content(self): test_a = {test_a}')             # +++
        
        self.parent.ui.welcome_label.setText(f'welcome user: <b>{test_a}</b>')             # +++