This should automate some widget's details dimension calculation:
from tkinter import *
import platform
root = Tk()
root.update()
screen_x = root.winfo_screenwidth()
screen_y = root.winfo_screenheight()
edge_x = root.winfo_rootx() - root.winfo_x()
edge_y = edge_x
title_y = root.winfo_rooty() - root.winfo_y() - edge_y
if platform.system() in ['Windows', 'Darwin']:
root.state('zoomed')
elif platform.system() in ['Linux', 'freebsd7']:
root.attributes('-zoomed', True)
root.update()
zoomed_screen_y = root.winfo_height()
task_bar_y = screen_y - zoomed_screen_y - title_y
print(task_bar_y)
root.destroy()
root = Tk()
root.geometry('{}x{}+0+0'.format(screen_x - 2 * edge_x, screen_y - title_y - 2 * edge_y - task_bar_y))
root.update()