StringsandConditional.py

def contains(big_string, little_string):
  if little_string in big_string:
    return True
  return False

def common_letters(string_one, string_two):
  common_letters = []
  for string_un in string_one:
      if string_un in string_two and string_un not in common_letters:
        common_letters.append(string_un)
  return common_letters