Fibonacci Series in Python

Fibonacci series in Python | In the Fibonacci series, the next element will be the sum of the previous two elements. The Fibonacci sequence is a series of numbers where a number is found by adding up the two numbers before it. Starting with 0 and 1, the sequence goes 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, and so on…

By definition, the first two numbers in the Fibonacci sequence are either 1 and 1, or 0 and 1, depending on the chosen starting point of the sequence, and each subsequent number is the sum of the previous two.

As a rule, the expression is X_n= X_n-1+ X_n-2

Fibonacci Sequence in Python

This python program using the if-else statement and while loop to display the Fibonacci sequence. We will take the n-th term while declaring the variables. Python program to display the Fibonacci sequence using while loop and finally, the result will be displayed on the screen.

# Python program to print fibonacci series up to n-th term

# take input
num = int(input('Enter number of terms: '))

# print fibonacci series
a, b = 0, 1
i = 0
    
# check if the number of terms is valid
if num <= 0:
    print('Please enter a positive integer.')

elif num == 1:
    print('The Fibonacci series: ')
    print(a)

else:
    print('The Fibonacci series: ')
    while i < num:
        print(a, end=' ')
        c = a + b
        a = b
        b = c
        i = i+1

Output for the different input values:-

Enter number of terms: 5
The Fibonacci series:
0 1 1 2 3

Enter number of terms: 13
The Fibonacci series:
0 1 1 2 3 5 8 13 21 34 55 89 144

Fibonacci Series in Python using For loop

In the previous program, we will use the while loop but in this program, display the Fibonacci sequence using for loop.

# Python program to print fibonacci series up to n-th term

# take input
num = int(input('Enter number of terms: '))

# print fibonacci series
a, b = 0, 1
   
# check if the number of terms is valid
if num <= 0:
    print('Please enter a positive integer.')

elif num == 1:
    print('The Fibonacci series: ')
    print(a)

else:
    print('The Fibonacci series: ')
    for i in range (1, num+1):
        print(a, end=' ')
        c = a + b
        a = b
        b = c

Output:-

Enter number of terms: 10
The Fibonacci series:
0 1 1 2 3 5 8 13 21 34

Find nth Fibonacci Number

# Python program to find n-th fibonacci number

# take input
num = int(input('Enter number of terms: '))

# print fibonacci term
a, b = 0, 1
    
# check if the number of terms is valid
if num <= 0:
    print('Please enter a positive integer.')

elif num == 1:
    print('The Fibonacci term is = ', end='')
    print(a)

else:
    print('The Fibonacci term is = ', end='')
    for i in range (2, num):
        c = a + b
        a = b
        b = c
    print(b)

Output for the different input values:-

Enter number of terms: 5
The Fibonacci term is = 3

Enter number of terms: 0
Please enter a positive integer.

Enter number of terms: 1
The Fibonacci term is = 0

Enter number of terms: 25
The Fibonacci term is = 46368

We can also find the Fibonacci series using the recursion technique. For more see:- Fibonacci series using recursion

Also See:- Find Factorial of a Number in Python

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