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Edit File: _elementpath.py
# cython: language_level=2 # # ElementTree # $Id: ElementPath.py 3375 2008-02-13 08:05:08Z fredrik $ # # limited xpath support for element trees # # history: # 2003-05-23 fl created # 2003-05-28 fl added support for // etc # 2003-08-27 fl fixed parsing of periods in element names # 2007-09-10 fl new selection engine # 2007-09-12 fl fixed parent selector # 2007-09-13 fl added iterfind; changed findall to return a list # 2007-11-30 fl added namespaces support # 2009-10-30 fl added child element value filter # # Copyright (c) 2003-2009 by Fredrik Lundh. All rights reserved. # # fredrik@pythonware.com # http://www.pythonware.com # # -------------------------------------------------------------------- # The ElementTree toolkit is # # Copyright (c) 1999-2009 by Fredrik Lundh # # By obtaining, using, and/or copying this software and/or its # associated documentation, you agree that you have read, understood, # and will comply with the following terms and conditions: # # Permission to use, copy, modify, and distribute this software and # its associated documentation for any purpose and without fee is # hereby granted, provided that the above copyright notice appears in # all copies, and that both that copyright notice and this permission # notice appear in supporting documentation, and that the name of # Secret Labs AB or the author not be used in advertising or publicity # pertaining to distribution of the software without specific, written # prior permission. # # SECRET LABS AB AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD # TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANT- # ABILITY AND FITNESS. IN NO EVENT SHALL SECRET LABS AB OR THE AUTHOR # BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY # DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, # WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS # ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE # OF THIS SOFTWARE. # -------------------------------------------------------------------- ## # Implementation module for XPath support. There's usually no reason # to import this module directly; the <b>ElementTree</b> does this for # you, if needed. ## from __future__ import absolute_import import re xpath_tokenizer_re = re.compile( "(" "'[^']*'|\"[^\"]*\"|" "::|" "//?|" r"\.\.|" r"\(\)|" r"[/.*:\[\]\(\)@=])|" r"((?:\{[^}]+\})?[^/\[\]\(\)@=\s]+)|" r"\s+" ) def xpath_tokenizer(pattern, namespaces=None): # ElementTree uses '', lxml used None originally. default_namespace = (namespaces.get(None) or namespaces.get('')) if namespaces else None parsing_attribute = False for token in xpath_tokenizer_re.findall(pattern): ttype, tag = token if tag and tag[0] != "{": if ":" in tag: prefix, uri = tag.split(":", 1) try: if not namespaces: raise KeyError yield ttype, "{%s}%s" % (namespaces[prefix], uri) except KeyError: raise SyntaxError("prefix %r not found in prefix map" % prefix) elif default_namespace and not parsing_attribute: yield ttype, "{%s}%s" % (default_namespace, tag) else: yield token parsing_attribute = False else: yield token parsing_attribute = ttype == '@' def prepare_child(next, token): tag = token[1] def select(result): for elem in result: for e in elem.iterchildren(tag): yield e return select def prepare_star(next, token): def select(result): for elem in result: for e in elem.iterchildren('*'): yield e return select def prepare_self(next, token): def select(result): return result return select def prepare_descendant(next, token): token = next() if token[0] == "*": tag = "*" elif not token[0]: tag = token[1] else: raise SyntaxError("invalid descendant") def select(result): for elem in result: for e in elem.iterdescendants(tag): yield e return select def prepare_parent(next, token): def select(result): for elem in result: parent = elem.getparent() if parent is not None: yield parent return select def prepare_predicate(next, token): # FIXME: replace with real parser!!! refs: # http://effbot.org/zone/simple-iterator-parser.htm # http://javascript.crockford.com/tdop/tdop.html signature = '' predicate = [] while 1: token = next() if token[0] == "]": break if token == ('', ''): # ignore whitespace continue if token[0] and token[0][:1] in "'\"": token = "'", token[0][1:-1] signature += token[0] or "-" predicate.append(token[1]) # use signature to determine predicate type if signature == "@-": # [@attribute] predicate key = predicate[1] def select(result): for elem in result: if elem.get(key) is not None: yield elem return select if signature == "@-='": # [@attribute='value'] key = predicate[1] value = predicate[-1] def select(result): for elem in result: if elem.get(key) == value: yield elem return select if signature == "-" and not re.match(r"-?\d+$", predicate[0]): # [tag] tag = predicate[0] def select(result): for elem in result: for _ in elem.iterchildren(tag): yield elem break return select if signature == ".='" or (signature == "-='" and not re.match(r"-?\d+$", predicate[0])): # [.='value'] or [tag='value'] tag = predicate[0] value = predicate[-1] if tag: def select(result): for elem in result: for e in elem.iterchildren(tag): if "".join(e.itertext()) == value: yield elem break else: def select(result): for elem in result: if "".join(elem.itertext()) == value: yield elem return select if signature == "-" or signature == "-()" or signature == "-()-": # [index] or [last()] or [last()-index] if signature == "-": # [index] index = int(predicate[0]) - 1 if index < 0: if index == -1: raise SyntaxError( "indices in path predicates are 1-based, not 0-based") else: raise SyntaxError("path index >= 1 expected") else: if predicate[0] != "last": raise SyntaxError("unsupported function") if signature == "-()-": try: index = int(predicate[2]) - 1 except ValueError: raise SyntaxError("unsupported expression") else: index = -1 def select(result): for elem in result: parent = elem.getparent() if parent is None: continue try: # FIXME: what if the selector is "*" ? elems = list(parent.iterchildren(elem.tag)) if elems[index] is elem: yield elem except IndexError: pass return select raise SyntaxError("invalid predicate") ops = { "": prepare_child, "*": prepare_star, ".": prepare_self, "..": prepare_parent, "//": prepare_descendant, "[": prepare_predicate, } # -------------------------------------------------------------------- _cache = {} def _build_path_iterator(path, namespaces): """compile selector pattern""" if path[-1:] == "/": path += "*" # implicit all (FIXME: keep this?) cache_key = (path,) if namespaces: # lxml originally used None for the default namespace but ElementTree uses the # more convenient (all-strings-dict) empty string, so we support both here, # preferring the more convenient '', as long as they aren't ambiguous. if None in namespaces: if '' in namespaces and namespaces[None] != namespaces['']: raise ValueError("Ambiguous default namespace provided: %r versus %r" % ( namespaces[None], namespaces[''])) cache_key += (namespaces[None],) + tuple(sorted( item for item in namespaces.items() if item[0] is not None)) else: cache_key += tuple(sorted(namespaces.items())) 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: # Python 3 _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 ## # Iterate over the matching nodes def iterfind(elem, path, namespaces=None): selector = _build_path_iterator(path, namespaces) result = iter((elem,)) for select in selector: result = select(result) return result ## # Find first matching object. def find(elem, path, namespaces=None): it = iterfind(elem, path, namespaces) try: return next(it) except StopIteration: return None ## # Find all matching objects. def findall(elem, path, namespaces=None): return list(iterfind(elem, path, namespaces)) ## # Find text for first matching object. def findtext(elem, path, default=None, namespaces=None): el = find(elem, path, namespaces) if el is None: return default else: return el.text or ''