from tkinter import *
import tkinter.messagebox

def save_data():
    try:
        fileD = open("deliveries.txt", "a")    
        fileD.write("Depot:\n") 
        fileD.write("%s\n" % depot.get()) 
        fileD.write("Description:\n") 
        fileD.write("%s\n" % description.get()) 
        fileD.write("Address:\n") 
        fileD.write("%s\n" % address.get("1.0", END)) 
        depot.set(None) 
        description.delete(0, END) 
        description.delete(0, END) 
        address.delete("1.0", END) 
    except Exception as ex:
        tkinter.messagebox.showerror("Error!", "Can't write to the file\n %s" % ex)


def read_depots(file): 
    depots = [] 
    depots_f = open(file) 
    for line in depots_f: 
        depots.append(line.rstrip()) 
    return depots 

app = Tk() 
app.title('Head-Ex Deliveries') 
Label(app, text = "Depot:").pack() 
depot = StringVar() 
depot.set(None) 

options = read_depots("depots.txt") 
OptionMenu(app, depot, *options).pack()

Label(app, text = "Description:").pack() 
description = Entry(app) 
description.pack() 
Label(app, text = "Address:").pack() 
address = Text(app) 
address.pack() 
Button(app, text = "Save", command = save_data).pack() 
app.mainloop()