Onkey function in Python Turtle not working for my input -

previously in program, used inputs in console player enter guesses want use onkey() function in python 3.6.1 turtle. want detect if player presses key , make string saying "guess='a'". want this:

import turtle  canvas=turtle.screen() t=turtle.pen() guess=0  def a():     guess='a'  canvas.onkey(a,'a') canvas.listen() 

obviously defined function each letter of alphabet. after this, when pressing 'a' , putting 'print(guess)', not printing 'a'.

the short answer forgot global statement in a() function it's reference guess local, not global. here's example implementation:

import turtle  def a():     global guess     guess += 'a'  def b():     global guess     guess += 'b'  def question():     print(guess)  guess = ''  canvas = turtle.screen()  canvas.onkey(a, 'a') canvas.onkey(b, 'b') canvas.onkey(question, '?')  canvas.listen()  canvas.mainloop() 

you can type 'a' , 'b' as want -- when type '?' string of letters you've built printed.