input: Write a function to calculate the sum of the digits in a given number.
  
  def sum_digits(num):
      total = 0
      while num > 0:
          digit = num % 10
          total += digit
          num = num // 10
      return total
  
  assert sum_digits(12345) == 15
  assert sum_digits(987) == 24
  assert sum_digits(5) == 5
  assert sum_digits(0) == 0
  assert sum_digits(10101) == 3
output: def sum_digits(num):
      total = 0
      while num > 0:
          digit = num % 10
          total += digit
          num = num // 10
      return total