def _build_path_iterator(path, namespaces):
 if (namespaces and ((None in namespaces) or ('' in namespaces))):
  raise ValueError('empty namespace prefix is not supported in ElementPath')
 if (path[(-1):] == '/'):
  path += '*'
 cache_key = (path, ((namespaces and tuple(sorted(namespaces.items()))) or None))
 try:
  return _cache[cache_key]
 except KeyError:
  pass
 if (len(_cache) > 100):
  _cache.clear()
 if (path[:1] == '/'):
  raise SyntaxError('cannot use absolute path on element')
 stream = iter(xpath_tokenizer(path, namespaces))
 try:
  _next = stream.next
 except AttributeError:
  _next = stream.__next__
 try:
  token = _next()
 except StopIteration:
  raise SyntaxError('empty path expression')
 selector = []
 while 1:
  try:
   selector.append(ops[token[0]](_next, token))
  except StopIteration:
   raise SyntaxError('invalid path')
  try:
   token = _next()
   if (token[0] == '/'):
    token = _next()
  except StopIteration:
   break
 _cache[cache_key] = selector
 return selector

def _build_path_iterator ( path , namespaces ) : if ( namespaces and ( ( None in namespaces ) or ( '' in namespaces ) ) ) : raise ValueError ( 'empty namespace prefix is not supported in ElementPath' ) if ( path [ ( - 1 ) : ] == '/' ) : path += '*' cache_key = ( path , ( ( namespaces and tuple ( sorted ( namespaces . items ( ) ) ) ) or None ) ) try : return _cache [ cache_key ] except KeyError : pass if ( len ( _cache ) > 100 ) : _cache . clear ( ) if ( path [ : 1 ] == '/' ) : raise SyntaxError ( 'cannot use absolute path on element' ) stream = iter ( xpath_tokenizer ( path , namespaces ) ) try : _next = stream . next except AttributeError : _next = stream . __next__ try : token = _next ( ) except StopIteration : raise SyntaxError ( 'empty path expression' ) selector = [ ] while 1 : try : selector . append ( ops [ token [ 0 ] ] ( _next , token ) ) except StopIteration : raise SyntaxError ( 'invalid path' ) try : token = _next ( ) if ( token [ 0 ] == '/' ) : token = _next ( ) except StopIteration : break _cache [ cache_key ] = selector return selector
compile selector pattern .