Work and pause timer

from datetime import datetime, timedelta
try:
    import tkinter as tk
except ImportError:
    import Tkinter as tk


def whole_seconds(time):
    return str(time).split('.')[0]

def update():
    if not pause_toggle.paused:
        timer.set(whole_seconds(datetime.now() - start_time - pause_timer.pause_time))
    else:
        this_pause = datetime.now() - pause_toggle.pause_start
        pause_timer.set(whole_seconds(this_pause + pause_timer.pause_time))
    root.after(100,update)

def pause_toggle():
    if pause_toggle.paused:
        pause_button['text'] = 'Start pause'
        pause_timer.pause_time += datetime.now() - pause_toggle.pause_start
    else:
        pause_button['text'] = 'Start work'
        pause_toggle.pause_start = datetime.now()
    pause_toggle.paused = not pause_toggle.paused
pause_toggle.paused = False

def make_label(text):
    tk.Label(root, text=text, font=("Helvetica", 16)).pack()
    text_var = tk.StringVar()
    tk.Label(root, textvariable=text_var, font=("Helvetica", 16)).pack()
    return text_var
    
root = tk.Tk()
root.title('Work and pause time')
root.geometry('240x180')
root.wm_attributes("-topmost", 1)

timer, pause_timer = make_label("Work time"), make_label("Pause time")

pause_button = tk.Button(root, text='Start pause', font=("Helvetica", 12, "bold"), command=pause_toggle)
pause_button.pack(side=tk.BOTTOM, pady=10)
        
pause_timer.pause_time = timedelta(0)
pause_timer.set(whole_seconds(pause_timer.pause_time))
start_time = datetime.now()
update()

root.mainloop()