input: Write a function to calculate the sum of the digits in a given number. Return the sum after adding all the digits together. If the given number is non-positive then return False.
  assert sum_digits(123)==6
  assert sum_digits(456)==15
  assert sum_digits(789)==24
  assert sum_digits(101)==2
  assert sum_digits(-123)==False
  assert sum_digits(0)==False
output: def sum_digits(n):
      if n <= 0:
          return False
      return sum(int(digit) for digit in str(n))