Global Variable Acting as a Local Variable in Python Tkinter

Question

I am trying to create a stopwatch in tkinter and I need a counter variable in order to be able to do so. However, the issue is that the variable is acting as a local one even though I declared it as global.

Here is my script:

import tkinter as tk

root = tk.Tk()


global counter
counter = 0


def go():
    label.config(text=str(counter))
    counter+=1
    root.after(1000,go2)
def go2():
    label.config(text=str(counter))
    counter+=1
    root.after(1000,go)
def stop():
    label.config(text=str(0))


gobutt = tk.Button(text = "Go", command = lambda: go())
stopbutt = tk.Button(text = "Stop", command = lambda: go2())
gobutt.pack()
stopbutt.pack()

label = tk.Label(text = "0")
label.pack()

root.mainloop()

Here is my error message:

Exception in Tkinter callback
Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/tkinter/__init__.py", line 1699, in __call__
    return self.func(*args)
  File "/Users/MinecraftMaster/Desktop/Python/Tests/TkinterTest/Tkinter Test.py", line 29, in <lambda>
    gobutt = tk.Button(text = "Go", command = lambda: go())
  File "/Users/MinecraftMaster/Desktop/Python/Tests/TkinterTest/Tkinter Test.py", line 18, in go
    label.config(text=str(counter))
UnboundLocalError: local variable 'counter' referenced before assignment

Asked By: Omaro_IB

||

Source

Answer 1

You should put global counter inside your function definitions so that the counter referenced inside your function is taken the one defined within the global scope

counter = 0

def go():
    global counter
    label.config(text=str(counter))
    counter+=1
    root.after(1000,go2)

def go2():
    global counter 
    label.config(text=str(counter))
    counter+=1
    root.after(1000,go)

Answered By: Sheldore

Global Variable Acting as a Local Variable in Python Tkinter

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