Python | Find Sum of all Numbers & Digits in an Alpha-Numeric String

Hello Everyone, in this tutorial we are going to write a simple program in python to calculate the sum of all numbers and digits in an alpha-numeric string.

Recently, I attend an interview on our campus. In the interview, the interviewer asked me to solve this problem.

This is a very simple problem, just the basics of a language are enough for one to solve this problem.

Algorithm to solve the problem:

1. Take the string input from the user and store it in variable n.

2. Initialize sum = 0, temp_num = 0

3. Now loop through all characters in that string.

4. If it is an alphabet, ignore it

5. If it is a numeric value, append it to variable temp_num until the next character is an alphabet and add temp_num to the sum.

6. Finally, print the sum at the end of the program. Thus gives the sum of all numbers in an alpha-numeric string.

1. Code for Sum of all Numbers in Alpha-Numeric String

Let's see how we can find the sum of numbers in alpha numeric string. So for example the string is s1s22s33, then numbers are 1, 22 and 33.

#1. Without Recursion

n = input("Enter an Alpha-Numeric String: ")
n_sum = 0
temp_num = ""
for i in n: 
    if( i.isalpha() ):
        if( temp_num != "" ):
            n_sum = n_sum + int(temp_num)
            temp_num = 0
    else:
        temp_num = str(temp_num) + str(i)
        
if( temp_num != "" ):
    n_sum = n_sum + int(temp_num)
    temp_num = 0
        
print(n_sum)

Enter an Alpha-Numeric String: s1s22s33
56

#2. With Recursion

Now we will see another way of implementing this, using recursion.

def sumOfNumbers(string, n, temp, sums):
    
    curr_val = string[n]

    if( curr_val.isalpha() ):
        sums = sums + int(temp)
        temp = 0
    else:
        temp = str(temp) + str(curr_val)
        
    if n == 0:
        return sums
    else:
        return sumOfNumbers(string, n-1, temp, sums)

string = input("Enter a Alpha Numeric String: ")
n = len(string) - 1
print( sumOfNumbers(string, n, temp=0, sums=0) )

Enter an Alpha-Numeric String: study24tonight77
101

2. Code for Sum of all Digits In Alpha-Numberic String

Here the algorithm is very simple, just add the value to the sum only if it is a numeric value and finally print sum. In this case, for string s1s22s33, digits are 1, 2, 2, 3 and 3.

#1 Without Recursion

string = input("Enter a Alpha-Numeric String: ")
sums = 0
for i in string:
    if( i.isnumeric() ):
        sums = sums+int(i)
print(sums)

Enter an Alpha-Numeric String: a11s22s55
16

#2 Using Recursion

def sumOfNumbers(string, n, sums):
    
    curr_val = string[n]
    if( curr_val.isnumeric() ):
        sums = sums + int(curr_val)
        
    if n == 0:
        return sums
    else:
        return sumOfNumbers(string, n-1, sums)

string = input("Enter a Alpha Numeric String: ")
n = len(string) - 1
print( sumOfNumbers(string, n, sums=0) )

Enter an Alpha-Numeric String: study24tonight77
20

Conclusion:

Pheww! This is a brief explanation of how to find the sum of all numbers and digits in an alpha-numeric string in python. I hope that you enjoyed the post. If you feel that this post is useful, please share it with your friends and colleagues.

Thanks for reading it till the end.

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