import random


def position_mod_uniform(in_str):
  """Select any position in the given input string with uniform likelihood.

     Return 0 is the string is empty.
  """

  if (in_str == ''):  # Empty input string
    return 0

  max_pos = len(in_str)-1

  pos = random.randint(0, max_pos)  # String positions start at 0

  return pos