Can I use a variable from a function that's inside of another class?

What I'm trying to do is create 1 window with 8 check boxes. The user will click the ones that are relevant and press "Calculate Job". That button should then open a new window that contains buttons/sections/whatever for only the options that were selected in window 1. Sounds ok... I have window 1 set up in class First. When I click the button it shows up the new window, great! But now I need to find a way to say "If any of these sections are selected then do something in window 2".

code:

from PyQt5 import QtWidgets
import sys
import qdarkstyle

class First(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super(First, self).__init__(parent)
        self.title = 'Job Price Calculator'
        self.left = 100
        self.top = 100
        self.width = 320
        self.height = 350
        self.initUI()
        self.dialog = Second()

    def initUI(self):
        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)

        self.data_processing = QtWidgets.QCheckBox('Data Processing', self)
        self.data_processing.move(50, 50)

        self.digital_print = QtWidgets.QCheckBox('Digital Print', self)
        self.digital_print.move(50, 100)

        self.calculate = QtWidgets.QPushButton('Calculate Job', self)
        self.calculate.move(100, 250)
        self.calculate.clicked.connect(self.on_button_click)

    def on_button_click(self):
        self.dialog.show()

class Second(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super(Second, self).__init__(parent)
        self.title = 'Job Specification'
        self.left = 500
        self.top = 100
        self.width = 1080
        self.height = 920
        self.initUI_specification()

    def initUI_specification(self):
        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)
        self.setStyleSheet(qdarkstyle.load_stylesheet_pyqt5())

        if self.data_processing.isChecked():
            self.data_processing_info()

        if self.digital_print.isChecked():
            self.digital_print_info()

    def data_processing_info(self):
        self.temp_button = QtWidgets.QPushButton('Temp Button', self)
        self.temp_button.move(100, 250)

    def digital_print_info(self):
        self.temp_button2 = QtWidgets.QPushButton('Temp Button 2', self)
        self.temp_button2.move(100, 450)

if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    main = First()
    main.show()
    sys.exit(app.exec_())

So what I want to do in class 'Second' is use the checkbox variable of self.data_processing to check if it has been enabled, if it has then I want to pull up a button in the Second gui window.

Is what I'm trying to do possible? Should I be thinking of a different way to do this? I'd like someones opinion on this if possible, and a little bit of guidance. I'd really appreciate the help, I've spent my whole weekend messing around with this and I'm just getting nowhere.

You need to call your second class inside first class when your checkbox is clicked

from PyQt5 import QtWidgets
import sys
import qdarkstyle

class First(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super(First, self).__init__(parent)
        self.title = 'Job Price Calculator'
        self.left = 100
        self.top = 100
        self.width = 320
        self.height = 350
        self.initUI()
        
    def initUI(self):
        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)

        self.data_processing = QtWidgets.QCheckBox('Data Processing', self)
        self.data_processing.move(50, 50)
        self.data_processing.stateChanged.connect(self.checkbox_clicked)

        self.digital_print = QtWidgets.QCheckBox('Digital Print', self)
        self.digital_print.move(50, 100)

        self.calculate = QtWidgets.QPushButton('Calculate Job', self)
        self.calculate.move(100, 250)
        self.calculate.clicked.connect(self.on_button_click)

        self.secondClass = Second()

    def on_button_click(self):
        self.dialog.show()
    
    def checkbox_clicked(self):
        if self.data_processing.isChecked():
            self.secondClass.data_processing_info()
            self.secondClass.show()
        else:
            self.secondClass.hide() #hide or close - as your requirement

class Second(QtWidgets.QMainWindow):
    def __init__(self, parent=None):
        super(Second, self).__init__(parent)
        self.title = 'Job Specification'
        self.left = 500
        self.top = 100
        self.width = 1080
        self.height = 920
        self.initUI_specification()

    def initUI_specification(self):
        self.setWindowTitle(self.title)
        self.setGeometry(self.left, self.top, self.width, self.height)
        self.setStyleSheet(qdarkstyle.load_stylesheet_pyqt5())


    def data_processing_info(self):
        self.temp_button = QtWidgets.QPushButton('Temp Button', self)
        self.temp_button.move(100, 250)

    def digital_print_info(self):
        self.temp_button2 = QtWidgets.QPushButton('Temp Button 2', self)
        self.temp_button2.move(100, 450)

if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    main = First()
    main.show()
    sys.exit(app.exec_())