How to stop time counter in Tkinter

[Yoriz]

After will return an id

self.after_id = self.LabelTestTime.after(1000, count)

when you want to stop call

tk.after_cancel(self.after_id)

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Actually your code is not quite set up right, when posting code it should be minimal but also runnable to reproduce your problem.
see the below example

import tkinter as tk


class Main:
    def __init__(self, root):
        self.counter = 0
        self.after_id = None
        self.frame = tk.Frame(root)
        self.label = tk.Label(self.frame, text="0")
        self.label.pack()

        btn_start = tk.Button(self.frame, text="Start",
                              command=self.on_btn_start)
        btn_start.pack()
        btn_stop = tk.Button(self.frame, text="Stop",
                             command=self.on_btn_stop)
        btn_stop.pack()
        btn_reset = tk.Button(self.frame, text="Reset",
                              command=self.on_btn_reset)
        btn_reset.pack()
        self.frame.pack()

    def on_btn_start(self):
        if not self.after_id:
            self.increase_counter()

    def on_btn_stop(self):
        if self.after_id:
            self.frame.after_cancel(self.after_id)
            self.after_id = None

    def on_btn_reset(self):
        self.on_btn_stop()
        self.counter = 0
        self.display_counter()

    def increase_counter(self):
        self.counter += 1
        self.display_counter()
        self.after_id = self.frame.after(1000, self.increase_counter)

    def display_counter(self):
        self.label['text'] = self.counter


root = tk.Tk()
main = Main(root)
root.mainloop()