Python Program for Fibonacci Series

In this post, you will learn how to write a python program for the Fibonacci series with an algorithm but before we jump into the program let’s understand first what is Fibonacci series and its algorithm to implement it.

What is Fibonacci Series?

The first two numbers are fixed which is 0,1 and the sum of the previous two numbers will give the next number and that number sequence is known as the Fibonacci series.

Example:

Algorithm for Fibonacci Series

Suppose you want to find the Fibonacci series for N numbers then the algorithm is:

1. Take input from the user (n)
2. Take two variables a and b, Initially a = 0 & b = 1.
3. if n == 1 then print(a)
4. if n == 2 then print(a,b)
5. i = 0
6. while i < n-2 do
7. c = a + b and print(c)
8. After printing c, update a = b & b = c.
9. At the end Increment i+=1.
10. End loop

Example using Algorithm:

Now we understood how to implement a python program to print the Fibonacci series with the help of the above example and algorithm so let us start writing a program for it.

Write a python program for Fibonacci Series using while loop

Before writing this program few programming concepts you have to know and those are:

1. if-elif-else &
2. while loop

Source code

# 0 1 1 2 3 5 8 13 ...
# a b c
#   a b c
#     a b c  
            
n = int(input("enter number for series :"))

a = 0
b = 1

if n <= 0:
    print('Enter valid number (>0)')

elif n == 1:
    print(a)

elif n == 2:
    print(a,b)

else:
    print(a, end=" ")
    print(b, end=" ")
    i = 0
    while i < n-2:
        c = a + b
        a=b
        b=c
        print(c, end = " ")
        i+=1

Output

enter number for series :11
0 1 1 2 3 5 8 13 21 34 55

Write a python program for Fibonacci Series using for loop

Before writing this program few programming concepts you have to know and those are:

1. if-elif-else &
2. for loop

Source code

n = int(input("enter number for series :"))

a = 0
b = 1

if n <= 0:
    print('Enter valid number (>0)')

elif n == 1:
    print(a)

elif n == 2:
    print(a,b)

else:
    print(a, end=" ")
    print(b, end=" ")
    
    for i in range(n-2):
        c = a + b
        a=b
        b=c
        print(c, end = " ")

Output

enter number for series :17
0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987

Write a python program for Fibonacci Series using the list

Before writing this program few programming concepts you have to know and those are:

1. if-elif-else &
2. for loop
3. python list

Source code

n = int(input("enter number for series :"))

a = 0
b = 1
fibo_list = []

if n <= 0:
    print('Enter valid number (>0)')

elif n == 1:
    fibo_list.append(a)
    print(fibo_list)

elif n == 2:
    fibo_list.append(a)
    fibo_list.append(b)
    print(fibo_list)

else:
    fibo_list.append(a)
    fibo_list.append(b)
    
    for i in range(n-2):
        c = a + b
        fibo_list.append(c)
        a=b
        b=c
    print(fibo_list)

Output

enter number for series :10
[0, 1, 1, 2, 3, 5, 8, 13, 21, 34]

Write a python program for Fibonacci Series using the function

Before writing this program few programming concepts you have to know and those are:

1. if-elif-else
2. while loop &
3. function in python

Source code

def fibonacci(num):
    a = 0
    b = 1
    if num == 1:
        print(a, end=" ")
    elif num == 2:
        print(a,b)
    else:
        print(a, end=" ")
        print(b, end=" ")
        i = 0
        while i < num-2:
            c = a + b
            a=b
            b=c
            print(c, end = " ")
            i+=1
    # return c
n = int(input("enter number for series :"))

if n<= 0:
    print('Enter number greater then 0')
else:
    fibonacci(n)

Output

enter number for series :5
0 1 1 2 3

Write a python program for Fibonacci Series using the recursion

Before writing this program few programming concepts you have to know and those are:

1. if-elif-else
2. while loop &
3. function in python
4. recursion

Source code

def fibo(n):
    a = 0
    b = 1
    if n == 1:
        return a
    elif n == 2:
        return b
    else:
        return fibo(n-1) + fibo(n-2)


n = int(input('ENter a number: '))
if n <=0:
    print('Enter valid number (>0)')
else:
    l = [str(fibo(i)) for i in range(1,n+1)]
    # print(l)

    print(','.join(l))

Output

ENter a number: 7
0,1,1,2,3,5,8