My first project

countdowntimer.py

import tkinter as tk 
from tkinter import ttk
import time   

counting = False

def count_down():
    global counting
    counting = True

    hour, minute, second = wanted_hour.get(), wanted_minute.get(), wanted_second.get()

    total_in_seconds = hour*3600 + minute*60 + second

    while total_in_seconds > -1 and counting:
        if second >= 0:
           
            if second > 9:
                second_var.set(f' {second} ') 
                second -= 1
                total_in_seconds -= 1
                root.update()
                time.sleep(1)
            else:
                 second_var.set(f' 0{second} ')
                 second -= 1
                 total_in_seconds -= 1
                 root.update()
                 time.sleep(1)

        elif minute > 0:
            if minute > 9:
                minute -= 1
                minute_var.set(f' {minute} ')
                second = 59
            else:
                 minute -= 1
                 minute_var.set(f' 0{minute} ') 
                 second = 59
        
        elif hour > 0:
            if hour > 9:
                hour -= 1
                hour_var.set(f' {hour} ')
                minute = 59
            else:
                 hour -= 1
                 hour_var.set(f' 0{hour} ')
                 minute = 59
    
    print(total_in_seconds) 
   
def edit():
    win = tk.Toplevel()
    win.config(padx=10, pady=10)

    h_lbl = tk.Label(win, text='Hour : ')
    m_lbl = tk.Label(win, text='Minute : ')
    s_lbl = tk.Label(win, text='Second : ')

    h_lbl.grid(column=0, row=0, ipadx=10)
    m_lbl.grid(column=0, row=1, ipadx=10)
    s_lbl.grid(column=0, row=2, ipadx=10)

    h_ent = tk.Entry(win)
    m_ent = tk.Entry(win)
    s_ent = tk.Entry(win)

    h_ent.grid(column=1, row=0)
    m_ent.grid(column=1, row=1)
    s_ent.grid(column=1, row=2)

    submit_btn = ttk.Button(win, text='Submit', 
                            command=lambda:submit(h_ent.get(),
                                           m_ent.get(),
                                           s_ent.get(),
                                           win)
)

    submit_btn.grid(columnspan=2, row=3, pady=10) 

def submit(h, m , s, w):
    global counting
    counting = False

    try:
        hour = int(h)
    except:
        hour = 0    

    try:                        
        minute = int(m)
    except:
        minute = 0  

    try:
        second = int(s)
    except:
        second = 0  

    if 25 > hour > 9:
        hour_var.set(f' {hour} ')
    elif hour < 10:
        hour_var.set(f' 0{hour} ')  
    else:
        hour = 24 
        hour_var.set(f' {hour} ')     

    if 25 > minute > 9:
        minute_var.set(f' {minute} ')
    elif minute < 10:
        minute_var.set(f' 0{minute} ')  
    else:
        minute = 59 
        minute_var.set(f' {minute} ')     
    if 25 > second > 9:
        second_var.set(f' {second} ')
    elif second < 10:
        second_var.set(f' 0{second} ')  
    else:
        second = 59 
        second_var.set(f' {second} ')     

    wanted_hour.set(hour)
    wanted_minute.set(minute)
    wanted_second.set(second)

    w.destroy()



root= tk.Tk()

wanted_hour = tk.IntVar()
wanted_minute = tk.IntVar()
wanted_second = tk.IntVar()

hour_var = tk.StringVar(value=' 00 ')
minute_var = tk.StringVar(value=' 00 ')
second_var = tk.StringVar(value=' 00 ')

hour_lbl = tk.Label(font=('Arial', 50), textvariable=hour_var)
colon1_lbl = tk.Label(font=('Arial', 50),text= ':')
minute_lbl = tk.Label(font=('Arial', 50), textvariable=minute_var)
colon2_lbl = tk.Label(font=('Arial', 50), text= ':')
second_lbl = tk.Label(font=('Arial', 50), textvariable=second_var)

hour_lbl.grid(column=0, row=0)
colon1_lbl.grid(column=1, row=0)
minute_lbl.grid(column=2, row=0)
colon2_lbl.grid(column=3, row=0)
second_lbl.grid(column=4, row=0)

btn_frame = tk.Frame(root) 
btn_frame.grid(column=2, row=1)

start_btn = ttk.Button(btn_frame, text='Start', command=count_down)
edit_btn = ttk.Button(btn_frame, text='Edit', command=edit) 

edit_btn.grid(column=0, row=0)
start_btn.grid(column=1, row=0)

tk.mainloop()