code: def isAlphanum(c):
      
      return ((c >= 'a' and c <= 'z') or (c >= '0' and c <= '9') or
              (c >= 'A' and c <= 'Z') or c == '_' or c == '$' or c == '\\' or (c is not None and ord(c) > 126));
docs: return true if the character is a letter, digit, underscore,
             dollar sign, or non-ASCII character.