get size of window tkinter

# Change window_name to the name of the window object, i.e. root
window_name.geometry("500x500")
# To ensure widgets resize:
widget_name.pack(fill="both", expand=True)

# Where w is a widget:
w.winfo_height()
w.winfo_width()

#import statement
from tkinter import *
#create GUI Tk() variable
gui = Tk()
#set window size
gui.geometry("widthxheight")