How to open two modules in one window, Python Tkinter - python-3.x

Question

I have a question: i am tossing the code from 2ch files, i have already lost ideas. Calling fileA.py opens a window for me with two buttons exit and start. Exit works but when I click start I need to open the second window fileB.pt. (I want both windows to open in one window) Seemingly works only problem I have is it doesn't open "window on window" but "docks underneath" and I have the effect of two windows open :/. Please help, thank you in advance:) Python 3.10
fileA.py
import tkinter as tk
from GUI.module.scale_of_img import get_scale
class FirstPage:
def __init__(self, root):
self.root = root
def get_settings(self):
# Window settings
self.root.title('....')
self.root.resizable(False, False)
self.root.geometry("1038x900")
if __name__ == '__main__':
first = FirstPage(tk.Tk())
first.get_run_first_page()
fileB.py
import tkinter as tk
"importy..."
''' The second side of the application '''
class SecondPage:
def __init__(self, root=None):
self.root = root
self.my_canvas = tk.Canvas(self.root, width=1038, height=678)
self.my_canvas.pack(fill="both", expand=True)
if __name__ == '__main__':
second = SecondPage(tk.Tk())
second.get_run()

Answer 1

in order to put two "windows" in the same "window" you need to put all items inside a Frame, which is basically a container than you can simply pack when you want everything to show and unpack when you want everything in it to disapear.
all items in the first window will be children of a frame and all items in the second window will be children of another frame, and to switch you just need to call pack_forget() on one and pack() on another.
for the first file
class FirstPage:
def __init__(self, root):
self.root = root
self.frame = tk.Frame(root)
self.frame.pack(expand=True)
def get_picture(self):
# all items inside this window must be children of self.frame
self.my_canvas = tk.Canvas(self.frame, width=1038, height=500)
...
def get_second_page(self):
from GUI.module.second_page import SecondPage
self.frame.pack_forget() # to hide first page
# self.frame.destroy() # if you are never brining it back
SecondPage(self.root).get_run()
and for the second file
class SecondPage:
def __init__(self, root=None):
self.root = root
self.frame = tk.Frame(root) # new frame
self.frame.pack(expand=True)
self.my_canvas = tk.Canvas(self.frame, width=1038, height=678)
self.my_canvas.pack(fill="both", expand=True)
def get_button(self):
# Add buttons
# all here should be children of self.frame now
button1 = tk.Button(self.frame, text="...", )
...
you could destroy the first frame when you switch over to save some resources if you don't intend to return to it ever again, but the difference in memory is negligible.

Answer 2

assuming what you want is another Tk window to open, you shouldn't give it the same root, instead use an instance of Toplevel
from tkinter import Toplevel
# class definition here
def get_second_page(self):
from GUI.module.second_page import SecondPage
SecondPage(Toplevel(self.root)).get_run()
passing the Toplevel as a child of self.root is necessary, but note that the two windows have different roots.
Edit: turns out this wasn't what the OP ment by "window on window" -_-, but it am keeping it here for other readers.