Fibonacci Series in Python

In this tutorial, we’ll learn how to write the Fibonacci series in python using multiple methods. The Fibonacci series is a series of numbers named after the Italian mathematician, called Fibonacci. A Fibonacci number is characterized by the recurrence relation given under:

Fn = Fn-1 + Fn-2
With F0 = 0 and F1 = 1.

What is Fibonacci Series?

The first two numbers of a Fibonacci series are 0 and 1. The rest of the numbers are obtained by the sum of the previous two numbers in the series. It means to say the nth digit is the sum of (n-1)_th and (n-2)_th digit. In mathematical terms, the sequence F_n of all Fibonacci numbers is defined by the recurrence relation.

Fibonacci Series Formula

Therefore, the formula for calculating the series Would Be as follows:

xn = xn-1 + xn-2 ; where
xn is term number "n"
xn-1 is the previous digit (n-1)
xn-2 is the term before that

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

In the above example, 0 and 1 will be the first two digits of the series. The Logic of the Fibonacci Series to calculate the next digit by adding the first two digits. In this case, 0 and 1. Therefore, we get 0 + 1 = 1. Hence 1 is printed as the third digit. The following digit is generated by using the second and third digits rather than using the initial digit. It’s done until the number of terms you want or requested by the user.

Algorithm for printing Fibonacci series using a while loop

Step 1: Input the 'n' value
Step 2: Initialize sum = 0, a = 0, b = 1 and count = 1
Step 3: while (count <= n)
Step 4: print sum
Step 5: Increment the count variable
Step 6: swap a and b
Step 7: sum = a + b
Step 8: while (count > n)
Step 9: End the algorithm
Step 10: Else
Step 11: Repeat from steps 4 to 7

Implementing the Fibonacci Series program in python

Fibonacci Sequence can be implemented both iteratively and recursively in Python.

#python program for fibonacci series until 'n' value
n = int(input("Enter the value of 'n': "))
 a = 0
 b = 1
 sum = 0
 count = 1
 print("Fibonacci Series: ", end = " ")
 while(count <= n):
  print(sum, end = " ")
   count += 1
   a = b
   b = sum
   sum = a + b

Recursive function algorithm for printing Fibonacci series

Step 1:If 'n' value is 0, return 0
Step 2:Else, if 'n' value is 1, return 1
Step 3:Else, recursively call the recursive function for the value (n - 2) + (n - 1)

Python Program to Print Fibonacci Series until ‘n’ value using recursion

def fib(digit):
 if digit <= 1:
   return (digit)
 else:
   return (fib(digit-1) + fib(digit-2))
   number_of_digit = 5
   for i in range(number_of_digit):
   print(fib(i))