How to Display Fibonacci Series in Python?

The Fibonacci Sequence is a series of numbers named after Italian mathematician, known as Fibonacci. It is simply the series of numbers which starts from 0 and 1 and then continued by the addition of the preceding two numbers. In this article, you will learn how to write a Python program to implement the Fibonacci series using multiple methods. Below pointers will be discussed:

• What is Fibonacci series?
• Python Program to write Fibonacci Sequence
  • Using Loop
  • Using Recursion

Let’s begin.

What is Fibonacci Series?

Fibonacci series is a series of numbers formed by the addition of the preceeding two numbers in the series.

Example of Fibonacci Series: 0,1,1,2,3,5

In the above example, 0 and 1 are the first two terms of the series. These two terms are printed directly. The third term is calculated by adding the first two terms. In this case 0 and 1. So, we get 0+1=1. Hence 1 is printed as the third term. The next term is generated by using the second and third term and not using the first term. It is done until the number of terms you want or requested by the user. In the above example, we have used five terms.

Next, let’s write a Python program to implement it.

Python Program to implement Fibonacci Sequence

Implementing Fibonacci sequence in Python programming language is the easiest! Now there are multiple ways to implement it, namely:

• Using Loop
• Using Recursion

Let’s see both the codes one by one.

Fibonacci Series using Loop

Loops in Python allow us to execute a group of statements several times. Let’s write a python program to implement Fibonacci Series using a loop.

# Enter number of terms needed                   #0,1,1,2,3,5....
a=int(input("Enter the terms"))
f=0                                         #first element of series
s=1                                         #second element of series
if a<=0:
    print("The requested series is
",f)
else:
    print(f,s,end=" ")
    for x in range(2,a):
        next=f+s                           
        print(next,end=" ")
        f=s
        s=next

Output: Enter the terms 5 0 1 1 2 3

Another way to program the Fibonacci series generation is by using recursion. Let’s dig deeper into it.

Python Program to Write Fibonacci Sequence Using Recursion

Recursion is the basic Python programming technique in which a function calls itself directly or indirectly. The corresponding function is called a recursive function. Using a recursive algorithm, certain problems can be solved quite easily. Let’s see how to use recursion to print first ‘n’ numbers of the Fibonacci Series in Python.

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Python Code:

def FibRecursion(n):  
   if n <= 1:  
       return n  
   else:  
       return(FibRecursion(n-1) + FibRecursion(n-2))  
 nterms = int(input("Enter the terms? "))  # take input from the user
 
if nterms <= 0:  # check if the number is valid 
   print("Please enter a positive integer")  
else:  
   print("Fibonacci sequence:")  
   for i in range(nterms):  
       print(FibRecursion(i))

Output: How many terms: 5
0 1 1 2 3

Explanation: In the above Python program, we use recursion to generate the Fibonacci sequence. The function FibRecursion is called recursively until we get the output. In the function, we first check if the number n is zero or one. If yes, we return the value of n. If not, we recursively call fibonacci with the values n-1 and n-2.

This brings us to the end of this ‘Fibonacci Series in Python’ article. We have learned how to programmatically print the Nth Fibonacci number using either loop statements or recursion.

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