resizable() method is used to allow Tkinter root window to change it's size according to the users need as well we can prohibit resizing of the Tkinter window. So, basically, if user wants to create a fixed size window, this method can be used. How to use:

-> import tkinter
-> root = Tk()
-> root.resizable(height = None, width = None)

Arguments to be passed:

-> In resizable() method user can pass either positive integer or True, to make the window resizable. -> To make window non-resizable user can pass 0 or False.

Code #1: Allowing root window to change it's size Python3 1==

# importing only  those functions
# which are needed
from tkinter import * 
from tkinter.ttk import * 
from time import strftime

# creating tkinter window
root = Tk()
root.title('Resizable')
root.geometry('250x100')

Label(root, text = 'It\'s resizable').pack(side = TOP, pady = 10)

# Allowing root window to change
# it's size according to user's need
root.resizable(True, True)

mainloop()

Output: Initial size - You may observe that the part inside blue circle is enabled i.e window is resizable and can be expanded. After resizing still the part inside the blue is enabled so you can still change the size of the window. Code #2: Restricting root window to change it's size (fixed size window). Python3 1==

# importing only  those functions
# which are needed
from tkinter import * 
from tkinter.ttk import * 
from time import strftime

# creating tkinter window
root = Tk()
root.title('Resizable')
root.geometry('250x100')

Label(root, text = 'It\'s non-resizable').pack(side = TOP, pady = 10)

# Restricting root window to change
# it's size according to user's need
root.resizable(0, 0)

mainloop()

Output: You may observe that the part inside the blue circle is disabled i.e size of the window cannot be altered.