import tkinter as tk
from tkinter.scrolledtext import ScrolledText

###     This program demonstrates a failure in using the lambda function with a loop variable.
###     The expected behaviour is that each command is build using the current value of the loop variable
###     but it seems that all commands ar build at the end of the function calling the loop.
###     Each command is build using the last value of the loop variable, if the variable is changed
###     sfter the end of the loop within the function this value is used instead

entries = ['alpha', 'beta', 'gamma', 'delta']                                   #   Menu entries to be used

def initGUI():
    """ GUI initialisation """
    global root, menu_ok, menu_nok, OUT
    
    root = tk.Tk()
    root.title("Menu demo")
    
    menubar = tk.Menu(root)
    menu_ok = tk.Menu(menubar, tearoff=0)                                       #   Prepare menu for working entries
    menubar.add_cascade(label="Working", menu=menu_ok)
    menu_nok = tk.Menu(menubar, tearoff=0)                                      #   Prepare menu for not working entries
    menubar.add_cascade(label="Failure", menu=menu_nok)
    root.config(menu=menubar)                                                   #   Add the menubar

    OUT = ScrolledText(root, width=40, height = 16)                             #   Prepare output area
    OUT.pack()
    return

def build_menu():
    """ Build up the menus """
    for name in entries:
        menu_nok.insert_command(tk.END, label=name, command=lambda:cmd(name))   #   create menu entry directly from loop
                                                                                #   using 'name' as menu entry label
                                                                                #   using 'name' as option for command
        setmen(name)                                                            #   create menu entry using function
        
    name="senseless"                                                            #   should not have any effect
                                                                                #   but all commands build inside the loop
                                                                                #   will use this value
                                                                                #   if not set the last value of loop
                                                                                #   is used for all commands
    return

def setmen(menu):
    """ add menu entry """
    menu_ok.insert_command(tk.END, label=menu, command=lambda:cmd(menu))        #   create menu entry identically as in the loop
    return

def cmd(param):
    """ print name ehere it is called from """
    OUT.insert(tk.INSERT, "called from %s\n" %param)                            #   Display output
    return
    
if __name__ == '__main__': 
    initGUI()
    build_menu()                                                                #   simulates calling configparser
    root.mainloop()