How to Find Fibonacci Numbers Iteratively in Python

Submitted by razormist on Saturday, August 23, 2025 - 23:03.

In this tutorial, we will learn how to program **"How to Find Fibonacci Numbers Iteratively in Python."** The objective is to calculate the Fibonacci sequence without using recursion. This tutorial will guide you step by step through the entire process of generating Fibonacci numbers based on the given input. By the end of this tutorial, you will have a solid understanding of how to implement this task effectively, helping you strengthen your problem-solving abilities and improve your Python coding skills.

This topic is straightforward to understand. Simply follow the instructions provided, and you will complete it with ease. The program will guide you step by step through the process of calculating the gravitational force. So, let’s dive into the coding process!

Getting Started:

First you will have to download & install the Python IDLE's, here's the link for the Integrated Development And Learning Environment for Python https://www.python.org/downloads/.

Creating Main Function

This is the main function of the application. The following code will display a simple GUI in terminal console that will display program. To do this, simply copy and paste these blocks of code into the IDLE text editor.

while True:
    print("\n================= Find Fibonacci Numbers Iteratively =================\n")
 
    try:
        a = int(input("Enter the first number of the series: "))
        b = int(input("Enter the second number of the series: "))
        n = int(input("Enter the number of terms needed: "))
 
        if n <= 0:
            print("Number of terms must be positive.")
            continue
 
        # Print Fibonacci sequence
        print("\nFibonacci Series:")
        if n == 1:
            print(a)
        elif n == 2:
            print(a, b)
        else:
            print(a, b, end=" ")
            for _ in range(n - 2):
                c = a + b
                print(c, end=" ")
                a, b = b, c
        print()  # newline
 
    except ValueError:
        print("Invalid input. Please enter integers only.")
        continue
 
    opt = input("\nDo you want to try again? (yes/no): ").strip().lower()
    if opt == 'no':
        print("Exiting program...")
        break
    elif opt != 'yes':
        print("Invalid choice. Exiting program...")
        break

This Python program generates Fibonacci numbers iteratively based on user input. It asks the user to enter the first two numbers of the series along with the number of terms to display. If the number of terms is valid, it prints the Fibonacci sequence accordingly—handling cases where only one or two terms are requested, or generating the sequence iteratively for more terms by repeatedly adding the last two numbers. The program includes input validation for integers, loops until the user chooses to exit, and ensures the sequence is displayed neatly in each run.

Output:

There you have it we successfully created How to Find Fibonacci Numbers Iteratively in Python. I hope that this simple tutorial help you to what you are looking for. For more updates and tutorials just kindly visit this site. Enjoy Coding!

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