Find the first un-repeated character in a string

Question

What is the quickest way to find the first character which only appears once in a string?

Answer 1

def first_non_repeated_character(string):
  chars = []
  repeated = []
  for character in string:
    if character in repeated:
        ... discard it.
    else if character in chars:
      chars.remove(character)
      repeated.append(character)
    else:
      if not character in repeated:
        chars.append(character)
  if len(chars):
    return chars[0]
  else:
    return False