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Editing: ElementPath.py
# # 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. # -------------------------------------------------------------------- # Licensed to PSF under a Contributor Agreement. # See https://www.python.org/psf/license for licensing details. ## # 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. ## import re xpath_tokenizer_re = re.compile( r"(" r"'[^']*'|\"[^\"]*\"|" r"::|" r"//?|" r"\.\.|" r"\(\)|" r"[/.*:\[\]\(\)@=])|" r"((?:\{[^}]+\})?[^/\[\]\(\)@=\s]+)|" r"\s+" ) def xpath_tokenizer(pattern, namespaces=None): default_namespace = 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) from None 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 get_parent_map(context): parent_map = context.parent_map if parent_map is None: context.parent_map = parent_map = {} for p in context.root.iter(): for e in p: parent_map[e] = p return parent_map def _is_wildcard_tag(tag): return tag[:3] == '{*}' or tag[-2:] == '}*' def _prepare_tag(tag): _isinstance, _str = isinstance, str if tag == '{*}*': # Same as '*', but no comments or processing instructions. # It can be a surprise that '*' includes those, but there is no # justification for '{*}*' doing the same. def select(context, result): for elem in result: if _isinstance(elem.tag, _str): yield elem elif tag == '{}*': # Any tag that is not in a namespace. def select(context, result): for elem in result: el_tag = elem.tag if _isinstance(el_tag, _str) and el_tag[0] != '{': yield elem elif tag[:3] == '{*}': # The tag in any (or no) namespace. suffix = tag[2:] # '}name' no_ns = slice(-len(suffix), None) tag = tag[3:] def select(context, result): for elem in result: el_tag = elem.tag if el_tag == tag or _isinstance(el_tag, _str) and el_tag[no_ns] == suffix: yield elem elif tag[-2:] == '}*': # Any tag in the given namespace. ns = tag[:-1] ns_only = slice(None, len(ns)) def select(context, result): for elem in result: el_tag = elem.tag if _isinstance(el_tag, _str) and el_tag[ns_only] == ns: yield elem else: raise RuntimeError(f"internal parser error, got {tag}") return select def prepare_child(next, token): tag = token[1] if _is_wildcard_tag(tag): select_tag = _prepare_tag(tag) def select(context, result): def select_child(result): for elem in result: yield from elem return select_tag(context, select_child(result)) else: if tag[:2] == '{}': tag = tag[2:] # '{}tag' == 'tag' def select(context, result): for elem in result: for e in elem: if e.tag == tag: yield e return select def prepare_star(next, token): def select(context, result): for elem in result: yield from elem return select def prepare_self(next, token): def select(context, result): yield from result return select def prepare_descendant(next, token): try: token = next() except StopIteration: return if token[0] == "*": tag = "*" elif not token[0]: tag = token[1] else: raise SyntaxError("invalid descendant") if _is_wildcard_tag(tag): select_tag = _prepare_tag(tag) def select(context, result): def select_child(result): for elem in result: for e in elem.iter(): if e is not elem: yield e return select_tag(context, select_child(result)) else: if tag[:2] == '{}': tag = tag[2:] # '{}tag' == 'tag' def select(context, result): for elem in result: for e in elem.iter(tag): if e is not elem: yield e return select def prepare_parent(next, token): def select(context, result): # FIXME: raise error if .. is applied at toplevel? parent_map = get_parent_map(context) result_map = {} for elem in result: if elem in parent_map: parent = parent_map[elem] if parent not in result_map: result_map[parent] = None yield parent return select def prepare_predicate(next, token): # FIXME: replace with real parser!!! refs: # http://javascript.crockford.com/tdop/tdop.html signature = [] predicate = [] while 1: try: token = next() except StopIteration: return if token[0] == "]": break if token == ('', ''): # ignore whitespace continue if token[0] and token[0][:1] in "'\"": token = "'", token[0][1:-1] signature.append(token[0] or "-") predicate.append(token[1]) signature = "".join(signature) # use signature to determine predicate type if signature == "@-": # [@attribute] predicate key = predicate[1] def select(context, 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(context, result): for elem in result: if elem.get(key) == value: yield elem return select if signature == "-" and not re.match(r"\-?\d+$", predicate[0]): # [tag] tag = predicate[0] def select(context, result): for elem in result: if elem.find(tag) is not None: yield elem return select if signature == ".='" or (signature == "-='" and not re.match(r"\-?\d+$", predicate[0])): # [.='value'] or [tag='value'] tag = predicate[0] value = predicate[-1] if tag: def select(context, result): for elem in result: for e in elem.findall(tag): if "".join(e.itertext()) == value: yield elem break else: def select(context, 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: raise SyntaxError("XPath position >= 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") if index > -2: raise SyntaxError("XPath offset from last() must be negative") else: index = -1 def select(context, result): parent_map = get_parent_map(context) for elem in result: try: parent = parent_map[elem] # FIXME: what if the selector is "*" ? elems = list(parent.findall(elem.tag)) if elems[index] is elem: yield elem except (IndexError, KeyError): pass return select raise SyntaxError("invalid predicate") ops = { "": prepare_child, "*": prepare_star, ".": prepare_self, "..": prepare_parent, "//": prepare_descendant, "[": prepare_predicate, } _cache = {} class _SelectorContext: parent_map = None def __init__(self, root): self.root = root # -------------------------------------------------------------------- ## # Generate all matching objects. def iterfind(elem, path, namespaces=None): # compile selector pattern if path[-1:] == "/": path = path + "*" # implicit all (FIXME: keep this?) cache_key = (path,) if namespaces: cache_key += tuple(sorted(namespaces.items())) try: selector = _cache[cache_key] except KeyError: if len(_cache) > 100: _cache.clear() if path[:1] == "/": raise SyntaxError("cannot use absolute path on element") next = iter(xpath_tokenizer(path, namespaces)).__next__ try: token = next() except StopIteration: return selector = [] while 1: try: selector.append(ops[token[0]](next, token)) except StopIteration: raise SyntaxError("invalid path") from None try: token = next() if token[0] == "/": token = next() except StopIteration: break _cache[cache_key] = selector # execute selector pattern result = [elem] context = _SelectorContext(elem) for select in selector: result = select(context, result) return result ## # Find first matching object. def find(elem, path, namespaces=None): return next(iterfind(elem, path, namespaces), 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): try: elem = next(iterfind(elem, path, namespaces)) return elem.text or "" except StopIteration: return default
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