Python Program to Find the Sum of Digits of a Number
easywhile loopPython
The standard way to take a number apart digit by digit — the same technique is used for reverse, palindrome and Armstrong programs.
The question
Read a positive integer and print the sum of its digits. Use a while loop with % 10 and // 10.
The code
program.py
n = int(input())
total = 0
while n > 0:
total += n % 10
n //= 10
print("Sum of digits =", total)Input
72050
Output
Sum of digits = 14
How it works
- 1n % 10 gives the last digit (1234 % 10 = 4).
- 2Add that digit to total.
- 3n //= 10 removes the last digit (1234 becomes 123).
- 4Repeat while n is greater than 0; when every digit is used, n becomes 0 and the loop ends.
Common mistakes
- Using / instead of // — n becomes 123.4 and the loop never works properly.
- Forgetting to change n inside the loop, which makes the loop run forever.
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