text: import tkinter as tk
  import tkinter.ttk as ttk
  import functions as funcs
  import datetime as dt # not being used yet
  import percent_change_window as pc
  import compound_interest_window as ci
  import market_days_window as md
  
  def main():
      # create main window
      root = tk.Tk()
      root.title('InvestiCalc')
      root.iconbitmap('images/investicalc.ico') # <- icon downloaded from https://icon-icons.com/icon/stocks-graphic-with-a-magnifier-tool/70602
      root.geometry('800x400')
  
      # set up notebook
      main = ttk.Notebook(root)
      main.pack(fill='both', expand=1)
  
      # declare frames to be assigned to tabs
      home     = ttk.Frame(main)
      pc_frame = pc.init_frame(main)
      ci_frame = ci.init_frame(main)
      md_frame = md.init_frame(main)
  
      # pack the frames in
      home    .pack(fill='both', expand=1)
      pc_frame.pack(fill='both', expand=1)
      ci_frame.pack(fill='both', expand=1)
      md_frame.pack(fill='both', expand=1)
  
      # declare tabs
      main.add(home, text='Home')
      main.add(pc_frame, text='Percent Change')
      main.add(ci_frame, text='Compound Interest')
      main.add(md_frame, text='Market Days')
  
      # hide the tabs from the start
      main.hide(1)
      main.hide(2)
      main.hide(3)
  
      # create buttons to open the tabs
      open_pc_btn = tk.Button(home, text='Calculate Percent Change', command=lambda: funcs.open_frame(main, 1))
      open_ci_btn = tk.Button(home, text='Calculate Compound Interest', command=lambda: funcs.open_frame(main, 2))
      open_md_btn = tk.Button(home, text='View Market Days', command=lambda: funcs.open_frame(main, 3))
  
      # pack the buttons
      open_pc_btn.pack()
      open_ci_btn.pack()
      open_md_btn.pack()
  
      # loop
      root.mainloop()
  
  if __name__ == '__main__':
      main()
  