7: SyntaxWarning: invalid escape sequence '\D'
  x = re.findall("\D", str)
['T', 'h', 'e', ' ', 'r', 'a', 'i', 'n', ' ', 'i', 'n', ' ', 'S', 'p', 'a', 'i', 'n']
Yes, there is at least one match!