In this article, we will learn about python program to find sum of digits of given number.

Getting Started

The task is to write a function that gets all the digits of number entered by user. Then, sum them and return it. For example,

If user enters 1234, then sum will be –

1 + 2 + 3 + 4 = 10

10 will be returned by function.

We can do so in many ways –

• Using str() and for Loop
• Using sum() Method
• Using Brute Force Approach
• Using Recursion
• Using ASCII Values
• One Liner Solution

Using str() and for Loop

We can find sum of digits of number in python using str and python for loop as shown below –

Pseudo Algorithm

• Initialize sum = 0
• Run a for loop on input value
• At each iteration, convert each value into integer using int. Then, add it into sum.
• At end of for loop value of variable sum is sum of all digits of given number.

 
def findSum(n):
    sum = 0
    for i in n:
        sum += int(i)
    return sum

n = input("Enter a number")
print(findSum(n))

Output:

 
Enter a number
5674
22

Using sum() Method

Pseudo Algorithm

• Our task is to convert input into python list, map() and strip() methods.
• Then, use built-in method, sum(), to get sum of elements present in list.

 
def findSum(num):
    numList = list(map(int, num.strip()))
    return sum(numList)

num = input("Enter a number")
print(findSum(num))

Output:

 
Enter a number
7768
28

Using Brute Force Approach

Pseudo Algorithm

• Initialize a variable sum = 0
• Run a while loop until value of variable num becomes 0.
• In each iteration, get the last digit of number and add it to sum.
• Then, divide the num by 10.
• At the end of while loop, value of sum is our desired result.

 
def findSum(num):
    sum = 0
    while(num != 0):
        sum = sum + num % 10
        num = num // 10
    return sum

num = int(input("Enter a number"))
print(findSum(num))

Output:

 
Enter a number
1234
10

Using Recursion

Pseudo Algorithm

• In each function call, get the last digit of number.
• After that, add it to result of same function call with number divided by 10.
• Break the function call when number becomes 0.

 
def findSum(num):
    if(num == 0):
        return num
    else:
        return (num % 10) + findSum(num // 10)

num = int(input("Enter a number"))
print(findSum(num))

Output:

 
Enter a number
6578
26

Improved Version

 
def findSum(num):
    return 0 if(num == 0) else (num % 10) + findSum(num // 10)

num = int(input("Enter a number"))
print(findSum(num))

Output:

 
Enter a number
1234
10

Using ASCII Values

Pseudo Algorithm

• Run a for loop for each digit of number.
• In each iteration, Difference between ASCII value current digit and 0 will give digit value.
• Then, add it to sum.
• At the end of for loop, value of variable sum is desired result.

 
def findSum(num):
    sum = 0
    for i in num:
        sum = sum + (ord(i) - ord('0'))
    return sum

num = input("Enter a number")
print(findSum(num))

Output:

 
Enter a number
768
21

One Liner Solution

 
n = [int(d) for d in input("Enter a number")]
print(sum(n))

Output:

 
Enter a number
345
12

That’s how we can write python program to find sum of digits of given number.

Learn about other python examples – https://tutorialwing.com/python-tutorial/

Reference: Official Doc