Returning variable from a function - python-3.x

Question

I have a main function page and i linked the next page with a button
when i click the button it executes a function in the main page but.
i want to use the result from the function in another file as a variable
########main.py
class Main(object):
def __init__(self,master):
self.master = master
mainFrame = Frame(self.master)
mainFrame.pack()
topFrame= Frame(mainFrame,width=1050,height =50, bg="#f8f8f8",padx =20, relief =SUNKEN,
borderwidth=2)
topFrame.pack(side=TOP,fill = X)
self.btnselfolder= Button(topFrame, text="Select Folder", compound=LEFT,
font="arial 12 bold", command=self.selectFolder)
self.btnselfolder.pack(side=LEFT)
def selectFolder(self):
print("folder")
return folder
################# selectfolder page
class Page2(Toplevel):
def __init__(self):
Toplevel.__init__(self)
self.geometry("450x300")
self.title("page2")
self.resizable(False,False)
self.topFrame = Frame(self, width=350,height=150, bg="white")
self.topFrame.pack(fill=X)
# call the function from main.py and it will give me the same output folder
y = selectFolder()

Answer 1

Since the selectFolder method is not static, you'll have to access it using instance. Like this:
main = Main()
folder = main.selectFolder()
folder should hold the value you returned.

Answer 2

I'm afraid when i just copied and pasted your code into my IDLE directly, it immediately presented me with naming errors. Not even a Tkinter window popped up. So to clear things up I would go about making a Tkinter window like the following. Also bare in mind I don't really use or know how to integrate classes with Tkinter itself, but I quickly learned how to by your mistakes :)
# import tkinter from the libraries
from tkinter import *
import os
# the Zen of Python
#import this
# declare the tkinter window variable
# scroll to bottom to see mainloop
root = Tk()
########main.py
# folder is not defined as a variable
# but i recommend looking into
# using system of which i imported
# for you. You can research how to
# use it yourself for good practice
# i am sorry if i am wrong about this
# but my impression is you're trying to
# use the OS to select a folder from a
# directory. So the 'selectFolder' function
# should not be declared as a method within the class
# therefore rendering the Page2 class useless.
def selectFolder():
print("folder")
# return will result in an error
# because it has not been declared as a variable
# return folder
class Main():
# all instances instantiated (created)
# within the __init__ method
# must be declared in the parentheses
def __init__(self, topFrame, btnselfolder):
# instantiate the topFrame object
self.topFrame = topFrame
# instantiate the btnselfolder
self.btnselfolder = btnselfolder
# pro tip - when having multiple
# arguments within an object, then
# to keep it clean and easy to read
# space out the code like i have for
# you. You should also read the "Zen of Python"
# which is at the top as 'import this'
# however i have commented it out for you
topFrame = Frame(root,
width=1050,
height = 50,
bg = "#f8f8f8",
padx = 20,
relief = SUNKEN,
borderwidth=2)
topFrame.pack(side=TOP, fill = X)
btnselfolder = Button(topFrame,
text = "Select Folder",
compound=LEFT,
font = "arial 12 bold",
command = selectFolder).pack()
# mainloop() method will keep the window open
# so that it doesn't appear for a millisecond
# and dissapear :)
root.mainloop()
# I hope this has been a big help
# Thanks for posting this question! :-)
# Enjoy your day, good luck and be safe in Lockdown!
Thanks again for the question, I thoroughly enjoyed solving it or at least giving you some guidence! :)