Thursday, September 26, 2019

Python Program to Display Fibonacci Series

In this post we’ll see how to write a Python program to display Fibonacci series.

Fibonacci series is a series of natural numbers where next number is equivalent to the sum of previous two numbers. Equation for the same can be written as follows-

fn = fn-1 + fn-2

The first two numbers in the Fibonacci sequence are either 1 and 1, or 0 and 1, and each subsequent number is the sum of the previous two numbers. Python programs in this post we'll display the Fibonacci series as - 0 1 1 2 3 5 8 ...

Python program for Fibonacci series can be written using recursion apart from writing using its iterative counterpart.

1. Fibonacci series using recursion. In a recursive function you should have a base case to exit the repeated calling of the same function. In case of Fibonacci series program that base case is when num is 0 and 1.

def fibonacci(num):
  if num < 0:
    print('Please enter non-negative integer')
  # For first two numbers
  if num == 0:
    return 0
  if num == 1:
    return 1
  return fibonacci(num - 1) + fibonacci(num - 2)
 
# running function after takking user input
num = int(input('Enter how many numbers needed in Fibonacci series- '))
for i in range(num):
  print(fibonacci(i), end=' ')

Output

Enter how many numbers needed in Fibonacci series- 10
0 1 1 2 3 5 8 13 21 34 

2. Fibonacci series program using iteration. Here for loop is used to iterate the passed number and in each iteration two previous numbers are added to get a new number in the series.

def fibonacci(num):
  num1 = 0
  num2 = 1
  series = 0
  for i in range(num):
    print(series, end=' ');
    num1 = num2;
    num2 = series;
    series = num1 + num2;

# running function after takking user input
num = int(input('Enter how many numbers needed in Fibonacci series- '))
fibonacci(num)

Output

Enter how many numbers needed in Fibonacci series- 8
0 1 1 2 3 5 8 13

That's all for this topic Python Program to Display Fibonacci Series. If you have any doubt or any suggestions to make please drop a comment. Thanks!

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