## 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:
# 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!