recursion - sum recursively, no loops

additup.py

def additup(num_list):
  ''' function that returns the sum of the passed list - without using loops; eg:
  sum([1, 2, 3, 4, 5]) -> 15
  sum([]) -> 0
  '''
  if len(num_list) == 1:
    return num_list[0]
  else:
    return num_list[len(num_list)-1] + additup(num_list[0:len(num_list)-1])

if __name__ == "__main__":
  l = [1, 2, 3, 4, 5]
  print(f'Sum recursively (no loops) over\n{l}\ngives: {additup(l)}')
  u = input('Would you like to input your own list? (y/n): ').lower()
  if u == 'y':
    ulist = list(input('The numbers in your list (no spaces): '))
    l = [int(x) for x in ulist]
    print(f'Sum recursively (no loops) over\n{l}\ngives: {additup(l)}')