code: def exists(self, regex):
          
          return self.search_full(regex, return_string=False, advance_pointer=False)
docs: See what :meth:`skip_until` would return without advancing the pointer.
  
              >>> s = Scanner("test string")
              >>> s.exists(' ')
              5
              >>> s.pos
              0
  
          Returns the number of characters matched if it does exist, or ``None``
          otherwise.