import tkinter as tk
from tkinter import ttk
import sys
sys.path.insert(0, '/absolute/path/to/main_page.py')

LARGEFONT = ("Verdana", 35)

class Page2(tk.Frame):
    def __init__(self, parent, controller):
        # Relative import attempt
        from project_folder import Page1, StartPage

        tk.Frame.__init__(self, parent)
        label = ttk.Label(self, text ="Page 2", font = LARGEFONT)
        label.grid(row = 0, column = 4, padx = 10, pady = 10)

        button1 = ttk.Button(self, text ="Page 1",
                             command = controller.show_frame(Page1))
        button1.grid(row = 1, column = 1, padx = 10, pady = 10)

        button2 = ttk.Button(self, text ="Startpage",
                             command = lambda : controller.show_frame(StartPage))
        button2.grid(row = 2, column = 1, padx = 10, pady = 10)