# Import the required libraries
from tkinter import *
from tkinter import ttk

# Create an instance of tkinter frame or window
win=Tk()

# Set the size of the window
win.geometry("700x350")

def update_width():
   frame.config(width=100)

# Create a frame
frame=Frame(win, bg="skyblue3", width=700, height=250)
frame.pack()

# Add a button in the main window
ttk.Button(win, text="Update", command=update_width).pack()

win.mainloop()