how to sum digits of a number in python

def sum_digits(n):
    s = 0
    while n:
        s += n % 10
        n //= 10
    return s

digit_sum = lambda s: sum(int(digit) for digit in str(s)) #without recursion

#sum of digits using recursion

dsum = 0 # we define dsum outside of the function so its value isn't reset every time the function gets called recursivley

def rdigit_sum(s):
    global dsum # making dsum 'global' allows us to use it a function
    if s: # checks if s has digits to add to dsum
        dsum += s%10 # adds the current units digit to dsum
        s = s//10 # removes the current units digit
    else: # if there are no digits left
        s = dsum  # this block reassigns s to dsum, then resets dsum to 0 so dsum doesn't already have a value if this function is called more than once in a program
        dsum = 0
        return s  
    return rdigit_sum(s) # this is the 'recursive' part of the program that calls the function again

number = 123 # the number you want to sum the digits of

sum_of_digits = sum(int(digit) for digit in str(number))

print(sum_of_digits)

number = 123 # the number you want summed up
sum_of_digits = 0 
for digit in str(number):
  sum_of_digits += int(digit)
  
print(sum_of_digits) # printing the final sum of number