please guys, i am not understanding this concept, please help me into this as i am new to python.

Write a function called digit_sum that takes a positive integer n as input and returns the sum of all that number’s digits. For example: digit_sum(1234) should return 10 which is 1 + 2 + 3 + 4. (Assume that the number you are given will always be positive.)

```
def digit_sum(x):
total = 0
while x > 0:
total += x % 10
x = x // 10
print x
return total
```