Python - TK - Dropdown Menu Info.txt

import tkinter as tk
from tkinter import ttk
import pandas as pd

customer_files_directory = 'C:/Users/botoole/Documents/BX STUFF/CODING DOCS/'


def on_select(event=None):
    # Retrieve the selected item from the dropdown list
    selection = dropdown.get()
    # Read the corresponding Excel file
    df = pd.read_excel(customer_files_directory + f'{selection}.xlsx')
    # Display the contents of the file in the text box
    text.config(state='normal')
    text.delete('1.0', tk.END)
    text.insert('1.0', df.to_string())
    text.config(state='disabled')


root = tk.Tk()
root.title('NetXPerts Customer Information Directory')

# Create the dropdown list
dropdown = ttk.Combobox(root, values=['Applied Test Systems', 'file2', 'file3'])
dropdown.current(0)
dropdown.bind('<<ComboboxSelected>>', on_select)
dropdown.pack()

# Create the button
button = tk.Button(root, text='Submit', command=on_select)
button.pack()

# Create the text box
text = tk.Text(root, state='disabled')
text.pack()

root.mainloop()