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#
# 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.
##
import re
xpath_tokenizer_re = re.compile(
"("
"'[^']*'|\"[^\"]*\"|"
"::|"
"//?|"
"\.\.|"
"\(\)|"
"[/.*:\[\]\(\)@=])|"
"((?:\{[^}]+\})?[^/\[\]\(\)@=\s]+)|"
"\s+"
)
def xpath_tokenizer(pattern, namespaces=None):
for token in xpath_tokenizer_re.findall(pattern):
tag = token[1]
if tag and tag[0] != "{" and ":" in tag:
try:
prefix, uri = tag.split(":", 1)
if not namespaces:
raise KeyError
yield token[0], "{%s}%s" % (namespaces[prefix], uri)
except KeyError:
raise SyntaxError("prefix %r not found in prefix map" % prefix)
else:
yield token
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[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(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("\d+$", predicate[0]):
# [tag]
tag = predicate[0]
def select(result):
for elem in result:
for _ in elem.iterchildren(tag):
yield elem
break
return select
if signature == "-='" and not re.match("\d+$", predicate[0]):
# [tag='value']
tag = predicate[0]
value = predicate[-1]
def select(result):
for elem in result:
for e in elem.iterchildren(tag):
if "".join(e.itertext()) == value:
yield elem
break
return select
if signature == "-" or signature == "-()" or signature == "-()-":
# [index] or [last()] or [last()-index]
if signature == "-":
index = int(predicate[0]) - 1
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 = path + "*" # implicit all (FIXME: keep this?)
try:
return _cache[path]
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[path] = 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:
try:
_next = it.next
except AttributeError:
return next(it)
else:
return _next()
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 ''
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