source: python/trunk/Lib/xml/etree/ElementPath.py

Last change on this file was 391, checked in by dmik, 11 years ago

python: Merge vendor 2.7.6 to trunk.
  • Property svn:eol-style set to native
File size: 9.3 KB
Line 
1#
2# ElementTree
3# $Id: ElementPath.py 3375 2008-02-13 08:05:08Z fredrik $
4#
5# limited xpath support for element trees
6#
7# history:
8# 2003-05-23 fl created
9# 2003-05-28 fl added support for // etc
10# 2003-08-27 fl fixed parsing of periods in element names
11# 2007-09-10 fl new selection engine
12# 2007-09-12 fl fixed parent selector
13# 2007-09-13 fl added iterfind; changed findall to return a list
14# 2007-11-30 fl added namespaces support
15# 2009-10-30 fl added child element value filter
16#
17# Copyright (c) 2003-2009 by Fredrik Lundh. All rights reserved.
18#
19# fredrik@pythonware.com
20# http://www.pythonware.com
21#
22# --------------------------------------------------------------------
23# The ElementTree toolkit is
24#
25# Copyright (c) 1999-2009 by Fredrik Lundh
26#
27# By obtaining, using, and/or copying this software and/or its
28# associated documentation, you agree that you have read, understood,
29# and will comply with the following terms and conditions:
30#
31# Permission to use, copy, modify, and distribute this software and
32# its associated documentation for any purpose and without fee is
33# hereby granted, provided that the above copyright notice appears in
34# all copies, and that both that copyright notice and this permission
35# notice appear in supporting documentation, and that the name of
36# Secret Labs AB or the author not be used in advertising or publicity
37# pertaining to distribution of the software without specific, written
38# prior permission.
39#
40# SECRET LABS AB AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD
41# TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANT-
42# ABILITY AND FITNESS. IN NO EVENT SHALL SECRET LABS AB OR THE AUTHOR
43# BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY
44# DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
45# WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
46# ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
47# OF THIS SOFTWARE.
48# --------------------------------------------------------------------
49
50# Licensed to PSF under a Contributor Agreement.
51# See http://www.python.org/psf/license for licensing details.
52
53##
54# Implementation module for XPath support. There's usually no reason
55# to import this module directly; the <b>ElementTree</b> does this for
56# you, if needed.
57##
58
59import re
60
61xpath_tokenizer_re = re.compile(
62 "("
63 "'[^']*'|\"[^\"]*\"|"
64 "::|"
65 "//?|"
66 "\.\.|"
67 "\(\)|"
68 "[/.*:\[\]\(\)@=])|"
69 "((?:\{[^}]+\})?[^/\[\]\(\)@=\s]+)|"
70 "\s+"
71 )
72
73def xpath_tokenizer(pattern, namespaces=None):
74 for token in xpath_tokenizer_re.findall(pattern):
75 tag = token[1]
76 if tag and tag[0] != "{" and ":" in tag:
77 try:
78 prefix, uri = tag.split(":", 1)
79 if not namespaces:
80 raise KeyError
81 yield token[0], "{%s}%s" % (namespaces[prefix], uri)
82 except KeyError:
83 raise SyntaxError("prefix %r not found in prefix map" % prefix)
84 else:
85 yield token
86
87def get_parent_map(context):
88 parent_map = context.parent_map
89 if parent_map is None:
90 context.parent_map = parent_map = {}
91 for p in context.root.iter():
92 for e in p:
93 parent_map[e] = p
94 return parent_map
95
96def prepare_child(next, token):
97 tag = token[1]
98 def select(context, result):
99 for elem in result:
100 for e in elem:
101 if e.tag == tag:
102 yield e
103 return select
104
105def prepare_star(next, token):
106 def select(context, result):
107 for elem in result:
108 for e in elem:
109 yield e
110 return select
111
112def prepare_self(next, token):
113 def select(context, result):
114 for elem in result:
115 yield elem
116 return select
117
118def prepare_descendant(next, token):
119 token = next()
120 if token[0] == "*":
121 tag = "*"
122 elif not token[0]:
123 tag = token[1]
124 else:
125 raise SyntaxError("invalid descendant")
126 def select(context, result):
127 for elem in result:
128 for e in elem.iter(tag):
129 if e is not elem:
130 yield e
131 return select
132
133def prepare_parent(next, token):
134 def select(context, result):
135 # FIXME: raise error if .. is applied at toplevel?
136 parent_map = get_parent_map(context)
137 result_map = {}
138 for elem in result:
139 if elem in parent_map:
140 parent = parent_map[elem]
141 if parent not in result_map:
142 result_map[parent] = None
143 yield parent
144 return select
145
146def prepare_predicate(next, token):
147 # FIXME: replace with real parser!!! refs:
148 # http://effbot.org/zone/simple-iterator-parser.htm
149 # http://javascript.crockford.com/tdop/tdop.html
150 signature = []
151 predicate = []
152 while 1:
153 token = next()
154 if token[0] == "]":
155 break
156 if token[0] and token[0][:1] in "'\"":
157 token = "'", token[0][1:-1]
158 signature.append(token[0] or "-")
159 predicate.append(token[1])
160 signature = "".join(signature)
161 # use signature to determine predicate type
162 if signature == "@-":
163 # [@attribute] predicate
164 key = predicate[1]
165 def select(context, result):
166 for elem in result:
167 if elem.get(key) is not None:
168 yield elem
169 return select
170 if signature == "@-='":
171 # [@attribute='value']
172 key = predicate[1]
173 value = predicate[-1]
174 def select(context, result):
175 for elem in result:
176 if elem.get(key) == value:
177 yield elem
178 return select
179 if signature == "-" and not re.match("\d+$", predicate[0]):
180 # [tag]
181 tag = predicate[0]
182 def select(context, result):
183 for elem in result:
184 if elem.find(tag) is not None:
185 yield elem
186 return select
187 if signature == "-='" and not re.match("\d+$", predicate[0]):
188 # [tag='value']
189 tag = predicate[0]
190 value = predicate[-1]
191 def select(context, result):
192 for elem in result:
193 for e in elem.findall(tag):
194 if "".join(e.itertext()) == value:
195 yield elem
196 break
197 return select
198 if signature == "-" or signature == "-()" or signature == "-()-":
199 # [index] or [last()] or [last()-index]
200 if signature == "-":
201 index = int(predicate[0]) - 1
202 else:
203 if predicate[0] != "last":
204 raise SyntaxError("unsupported function")
205 if signature == "-()-":
206 try:
207 index = int(predicate[2]) - 1
208 except ValueError:
209 raise SyntaxError("unsupported expression")
210 else:
211 index = -1
212 def select(context, result):
213 parent_map = get_parent_map(context)
214 for elem in result:
215 try:
216 parent = parent_map[elem]
217 # FIXME: what if the selector is "*" ?
218 elems = list(parent.findall(elem.tag))
219 if elems[index] is elem:
220 yield elem
221 except (IndexError, KeyError):
222 pass
223 return select
224 raise SyntaxError("invalid predicate")
225
226ops = {
227 "": prepare_child,
228 "*": prepare_star,
229 ".": prepare_self,
230 "..": prepare_parent,
231 "//": prepare_descendant,
232 "[": prepare_predicate,
233 }
234
235_cache = {}
236
237class _SelectorContext:
238 parent_map = None
239 def __init__(self, root):
240 self.root = root
241
242# --------------------------------------------------------------------
243
244##
245# Generate all matching objects.
246
247def iterfind(elem, path, namespaces=None):
248 # compile selector pattern
249 if path[-1:] == "/":
250 path = path + "*" # implicit all (FIXME: keep this?)
251 try:
252 selector = _cache[path]
253 except KeyError:
254 if len(_cache) > 100:
255 _cache.clear()
256 if path[:1] == "/":
257 raise SyntaxError("cannot use absolute path on element")
258 next = iter(xpath_tokenizer(path, namespaces)).next
259 token = next()
260 selector = []
261 while 1:
262 try:
263 selector.append(ops[token[0]](next, token))
264 except StopIteration:
265 raise SyntaxError("invalid path")
266 try:
267 token = next()
268 if token[0] == "/":
269 token = next()
270 except StopIteration:
271 break
272 _cache[path] = selector
273 # execute selector pattern
274 result = [elem]
275 context = _SelectorContext(elem)
276 for select in selector:
277 result = select(context, result)
278 return result
279
280##
281# Find first matching object.
282
283def find(elem, path, namespaces=None):
284 try:
285 return iterfind(elem, path, namespaces).next()
286 except StopIteration:
287 return None
288
289##
290# Find all matching objects.
291
292def findall(elem, path, namespaces=None):
293 return list(iterfind(elem, path, namespaces))
294
295##
296# Find text for first matching object.
297
298def findtext(elem, path, default=None, namespaces=None):
299 try:
300 elem = iterfind(elem, path, namespaces).next()
301 return elem.text or ""
302 except StopIteration:
303 return default
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