324 lines
10 KiB
Python
324 lines
10 KiB
Python
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#
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# ElementTree
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# $Id: ElementPath.py 3375 2008-02-13 08:05:08Z fredrik $
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#
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# limited xpath support for element trees
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#
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# history:
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# 2003-05-23 fl created
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# 2003-05-28 fl added support for // etc
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# 2003-08-27 fl fixed parsing of periods in element names
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# 2007-09-10 fl new selection engine
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# 2007-09-12 fl fixed parent selector
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# 2007-09-13 fl added iterfind; changed findall to return a list
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# 2007-11-30 fl added namespaces support
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# 2009-10-30 fl added child element value filter
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#
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# Copyright (c) 2003-2009 by Fredrik Lundh. All rights reserved.
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#
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# fredrik@pythonware.com
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# http://www.pythonware.com
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#
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# --------------------------------------------------------------------
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# The ElementTree toolkit is
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#
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# Copyright (c) 1999-2009 by Fredrik Lundh
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#
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# By obtaining, using, and/or copying this software and/or its
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# associated documentation, you agree that you have read, understood,
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# and will comply with the following terms and conditions:
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#
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# Permission to use, copy, modify, and distribute this software and
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# its associated documentation for any purpose and without fee is
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# hereby granted, provided that the above copyright notice appears in
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# all copies, and that both that copyright notice and this permission
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# notice appear in supporting documentation, and that the name of
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# Secret Labs AB or the author not be used in advertising or publicity
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# pertaining to distribution of the software without specific, written
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# prior permission.
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#
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# SECRET LABS AB AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD
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# TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANT-
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# ABILITY AND FITNESS. IN NO EVENT SHALL SECRET LABS AB OR THE AUTHOR
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# BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY
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# DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
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# WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
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# ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
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# OF THIS SOFTWARE.
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# --------------------------------------------------------------------
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# Licensed to PSF under a Contributor Agreement.
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# See http://www.python.org/psf/license for licensing details.
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##
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# Implementation module for XPath support. There's usually no reason
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# to import this module directly; the <b>ElementTree</b> does this for
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# you, if needed.
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##
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import re
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xpath_tokenizer_re = re.compile(
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r"("
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r"'[^']*'|\"[^\"]*\"|"
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r"::|"
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r"//?|"
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r"\.\.|"
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r"\(\)|"
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r"[/.*:\[\]\(\)@=])|"
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r"((?:\{[^}]+\})?[^/\[\]\(\)@=\s]+)|"
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r"\s+"
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)
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def xpath_tokenizer(pattern, namespaces=None):
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for token in xpath_tokenizer_re.findall(pattern):
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tag = token[1]
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if tag and tag[0] != "{" and ":" in tag:
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try:
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prefix, uri = tag.split(":", 1)
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if not namespaces:
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raise KeyError
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yield token[0], "{%s}%s" % (namespaces[prefix], uri)
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except KeyError:
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raise SyntaxError("prefix %r not found in prefix map" % prefix) from None
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else:
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yield token
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def get_parent_map(context):
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parent_map = context.parent_map
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if parent_map is None:
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context.parent_map = parent_map = {}
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for p in context.root.iter():
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for e in p:
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parent_map[e] = p
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return parent_map
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def prepare_child(next, token):
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tag = token[1]
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def select(context, result):
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for elem in result:
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for e in elem:
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if e.tag == tag:
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yield e
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return select
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def prepare_star(next, token):
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def select(context, result):
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for elem in result:
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yield from elem
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return select
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def prepare_self(next, token):
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def select(context, result):
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yield from result
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return select
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def prepare_descendant(next, token):
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try:
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token = next()
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except StopIteration:
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return
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if token[0] == "*":
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tag = "*"
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elif not token[0]:
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tag = token[1]
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else:
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raise SyntaxError("invalid descendant")
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def select(context, result):
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for elem in result:
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for e in elem.iter(tag):
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if e is not elem:
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yield e
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return select
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def prepare_parent(next, token):
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def select(context, result):
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# FIXME: raise error if .. is applied at toplevel?
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parent_map = get_parent_map(context)
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result_map = {}
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for elem in result:
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if elem in parent_map:
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parent = parent_map[elem]
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if parent not in result_map:
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result_map[parent] = None
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yield parent
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return select
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def prepare_predicate(next, token):
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# FIXME: replace with real parser!!! refs:
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# http://effbot.org/zone/simple-iterator-parser.htm
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# http://javascript.crockford.com/tdop/tdop.html
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signature = []
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predicate = []
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while 1:
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try:
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token = next()
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except StopIteration:
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return
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if token[0] == "]":
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break
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if token == ('', ''):
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# ignore whitespace
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continue
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if token[0] and token[0][:1] in "'\"":
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token = "'", token[0][1:-1]
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signature.append(token[0] or "-")
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predicate.append(token[1])
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signature = "".join(signature)
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# use signature to determine predicate type
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if signature == "@-":
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# [@attribute] predicate
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key = predicate[1]
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def select(context, result):
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for elem in result:
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if elem.get(key) is not None:
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yield elem
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return select
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if signature == "@-='":
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# [@attribute='value']
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key = predicate[1]
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value = predicate[-1]
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def select(context, result):
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for elem in result:
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if elem.get(key) == value:
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yield elem
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return select
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if signature == "-" and not re.match(r"\-?\d+$", predicate[0]):
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# [tag]
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tag = predicate[0]
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def select(context, result):
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for elem in result:
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if elem.find(tag) is not None:
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yield elem
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return select
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if signature == ".='" or (signature == "-='" and not re.match(r"\-?\d+$", predicate[0])):
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# [.='value'] or [tag='value']
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tag = predicate[0]
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value = predicate[-1]
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if tag:
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def select(context, result):
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for elem in result:
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for e in elem.findall(tag):
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if "".join(e.itertext()) == value:
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yield elem
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break
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else:
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def select(context, result):
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for elem in result:
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if "".join(elem.itertext()) == value:
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yield elem
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return select
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if signature == "-" or signature == "-()" or signature == "-()-":
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# [index] or [last()] or [last()-index]
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if signature == "-":
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# [index]
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index = int(predicate[0]) - 1
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if index < 0:
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raise SyntaxError("XPath position >= 1 expected")
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else:
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if predicate[0] != "last":
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raise SyntaxError("unsupported function")
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if signature == "-()-":
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try:
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index = int(predicate[2]) - 1
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except ValueError:
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raise SyntaxError("unsupported expression")
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if index > -2:
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raise SyntaxError("XPath offset from last() must be negative")
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else:
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index = -1
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def select(context, result):
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parent_map = get_parent_map(context)
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for elem in result:
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try:
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parent = parent_map[elem]
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# FIXME: what if the selector is "*" ?
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elems = list(parent.findall(elem.tag))
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if elems[index] is elem:
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yield elem
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except (IndexError, KeyError):
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pass
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return select
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raise SyntaxError("invalid predicate")
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ops = {
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"": prepare_child,
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"*": prepare_star,
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".": prepare_self,
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"..": prepare_parent,
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"//": prepare_descendant,
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"[": prepare_predicate,
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}
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_cache = {}
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class _SelectorContext:
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parent_map = None
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def __init__(self, root):
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self.root = root
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# --------------------------------------------------------------------
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##
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# Generate all matching objects.
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def iterfind(elem, path, namespaces=None):
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# compile selector pattern
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cache_key = (path, None if namespaces is None
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else tuple(sorted(namespaces.items())))
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if path[-1:] == "/":
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path = path + "*" # implicit all (FIXME: keep this?)
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try:
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selector = _cache[cache_key]
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except KeyError:
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if len(_cache) > 100:
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_cache.clear()
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if path[:1] == "/":
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raise SyntaxError("cannot use absolute path on element")
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next = iter(xpath_tokenizer(path, namespaces)).__next__
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try:
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token = next()
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except StopIteration:
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return
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selector = []
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while 1:
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try:
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selector.append(ops[token[0]](next, token))
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except StopIteration:
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raise SyntaxError("invalid path") from None
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try:
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token = next()
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if token[0] == "/":
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token = next()
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except StopIteration:
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break
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_cache[cache_key] = selector
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# execute selector pattern
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result = [elem]
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context = _SelectorContext(elem)
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for select in selector:
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result = select(context, result)
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return result
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##
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# Find first matching object.
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def find(elem, path, namespaces=None):
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return next(iterfind(elem, path, namespaces), None)
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##
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# Find all matching objects.
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def findall(elem, path, namespaces=None):
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return list(iterfind(elem, path, namespaces))
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##
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# Find text for first matching object.
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def findtext(elem, path, default=None, namespaces=None):
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try:
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elem = next(iterfind(elem, path, namespaces))
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return elem.text or ""
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except StopIteration:
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return default
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