How to set Font size to fit a specific width of the frame in tkinter

with .config you can adjust Attributes after you placed it. Now you can adjust the window size with the len() of your string. I hope it helps.

import tkinter as tk

def adjust_Window(canvas, text):

    canvas.config(width=len(text)*50)

def main():
    root = tk.Tk()

    canvas = tk.Canvas(root, width=500, height=500)
    canvas.pack()

    adjust_Window(canvas, "i hope it helps <3")

    root.mainloop()


if __name__ == '__main__':
    main()

Easier way to do this:

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():
   l.configure(text='Hotel Raj Kundra and Family Resturant', background='blue', foreground='white', font=("Calibri,8,itlaic"))
   

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

# Add a button in the main window
ttk.Button(win, text="Update", command=update_width).pack()
l = ttk.Label(win, background='red', text="so how it will automatically adjust in this size of window without wrapped the text. just fit in the window siz" , font=("Calibri,32,Bold"))
l.pack()
          
win.mainloop()

Result widest:

Result to shrink: