How to use Tkinter to open file in folder using dropdown

You cannot just select and read a file's contents from tkinter. You have to write some other scripts for that reading part.

What the selection of filename does from tkinter combo box, is nothing but, get the particular file name as a string type.

However, in Python it's pretty straight forward to read a .xlsx file.You can use Pandas module for that.

I have written the code for you to read the file, (but you have to install pandas)

from functools import partialimport osimport tkinter as tkfrom tkinter import ttk#import tkinter as tkfrom tkinter import filedialog, messagebox, ttkimport pandasdef get_selected_file_name(file_menu):    filename = file_menu.get()    print("file selected:", filename)    reader = pandas.read_excel(filename)  # code to read excel file    # now you can use the `reader` object to get the file datafolder = os.path.realpath('./test_folder')filelist = [fname for fname in os.listdir(folder)]master = tk.Tk()master.geometry('1200x800')master.title('Select a file')optmenu = ttk.Combobox(master, values=filelist, state='readonly')optmenu.pack(fill='x')button_select = tk.Button(master, text="Read File",                          width=20,                          height=7,                          compound=tk.CENTER,                          command=partial(get_selected_file_name, optmenu))button_select.pack(side=tk.RIGHT)master.mainloop()

The window should look somewhat like this:

I'd explore using the filedialog module in tkinter.

import tkinter as tkfrom tkinter import filedialogdef load_file():    f_in = filedialog.askopenfilename( filetypes = [ ( 'Python', '*.py' ) ])  # Change to appropriate extension.    if len( f_in ) > 0:        with open( f_in, 'r' ) as file:            filedata = file.read()        print( filedata )   # printed to the terminal for simplicity.                            # process it as required.root = tk.Tk()tk.Button( root, text = 'Find File', command = load_file ).grid()root.mainloop()

askopenfilename allows a user to navigate the folder tree to find the correct file. Basic documentation