Automatically Maximize Window in Tkinter 

If  You Use win.state("zoomed")  in tkinter, Your Window will go to Automatically Maximize. Here win is the main window.

from tkinter import *
win= Tk()
win.title("Automatically Maximize Window")
win.geometry("800x350+450+86")
win.config(bg="#CAFF70")
win.state("zoomed")           #It Maximize Automatically
lbl= Label(win, text= "Automatically Maximize Window", font=("Time New Roman", 35,"bold"), bg="#CAFF70", fg="red")
lbl.pack(pady=60)
win.mainloop()

Write Down Code Your Code Editor. To show Your Output. If Use Pycharm Press Shift+F10 and Show Your Output.

Your Window is now in Full Screen 

Lets Enjoy ............................