Fibonacci GUI in Python

fib.py

# fib.py
# Written by Lev Grachov

# Import Tkinter
# If you get module not installed, then run this command:
# For Linux: `sudo apt-get install python3-tk`
# For Windows: `pip install tk`
# For macOS: `brew install python-tk`
from tkinter.simpledialog import askinteger
from tkinter import *
from tkinter import messagebox

# Create the window
Win = Tk()
Win.geometry("300x130")
print("Window created")

# Make a function to ask for the input
def askInput():
   Num = askinteger("Fibonacci", "Input the Integer")
   print("The number inputted is " + str(Num))
   fibonacciOf(Num)
   
# Fibonacci function
def fibonacciOf(n):
    # Validate the value of n
    if not (isinstance(n, int) and n >= 0):
        raise ValueError(f'Positive integer number expected, got "{n}"')

    # Handle the base cases
    if n in {0, 1}:
        return n

    previous, fibNumber = 0, 1
    for _ in range(2, n + 1):
        # Compute the next Fibonacci number, remember the previous one
        previous, fibNumber = fibNumber, previous + fibNumber
    print("Fibonacci has been calculated")
    Result.config(text = fibNumber)
    print("Result label has been set to result")
    return fibNumber

# Create the fibonacci button
But = Button(Win, text ="Fibonacci", command = askInput)
But.place(x=0,y=0)
print("Created button")

# Create the fibonacci result text box
Result = Label(Win, text="Result will be shown here")
Result.place(x=0,y=35)
print("Created textbox")

# Function to say that program window has been closed
try:
  Win.mainloop()
except KeyboardInterrupt:
  print("Program window has been closed. Stopping")