Source Code for Module nltk.etree.ElementPath

  1  # 
  2  # ElementTree 
  3  # $Id: ElementPath.py 1858 2004-06-17 21:31:41Z 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  # 
 12  # Copyright (c) 2003-2004 by Fredrik Lundh.  All rights reserved. 
 13  # 
 14  # [email protected] 
 15  # http://www.pythonware.com 
 16  # 
 17  # -------------------------------------------------------------------- 
 18  # The ElementTree toolkit is 
 19  # 
 20  # Copyright (c) 1999-2004 by Fredrik Lundh 
 21  # 
 22  # By obtaining, using, and/or copying this software and/or its 
 23  # associated documentation, you agree that you have read, understood, 
 24  # and will comply with the following terms and conditions: 
 25  # 
 26  # Permission to use, copy, modify, and distribute this software and 
 27  # its associated documentation for any purpose and without fee is 
 28  # hereby granted, provided that the above copyright notice appears in 
 29  # all copies, and that both that copyright notice and this permission 
 30  # notice appear in supporting documentation, and that the name of 
 31  # Secret Labs AB or the author not be used in advertising or publicity 
 32  # pertaining to distribution of the software without specific, written 
 33  # prior permission. 
 34  # 
 35  # SECRET LABS AB AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD 
 36  # TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANT- 
 37  # ABILITY AND FITNESS.  IN NO EVENT SHALL SECRET LABS AB OR THE AUTHOR 
 38  # BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY 
 39  # DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, 
 40  # WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS 
 41  # ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE 
 42  # OF THIS SOFTWARE. 
 43  # -------------------------------------------------------------------- 
 44   
 45  # Licensed to PSF under a Contributor Agreement. 
 46  # See http://www.python.org/2.4/license for licensing details. 
 47   
 48  ## 
 49  # Implementation module for XPath support.  There's usually no reason 
 50  # to import this module directly; the <b>ElementTree</b> does this for 
 51  # you, if needed. 
 52  ## 
 53   
 54  import re 
 55   
 56  xpath_tokenizer = re.compile( 
 57      "(::|\.\.|\(\)|[/.*:\[\]\(\)@=])|((?:\{[^}]+\})?[^/:\[\]\(\)@=\s]+)|\s+" 
 58      ).findall 
 59   
 60 -class xpath_descendant_or_self: 
 61      pass 
 62   
 63  ## 
 64  # Wrapper for a compiled XPath. 
 65   
 66 -class Path: 
 67   
 68      ## 
 69      # Create an Path instance from an XPath expression. 
 70   
 71 -    def __init__(self, path): 
 72          tokens = xpath_tokenizer(path) 
 73          # the current version supports 'path/path'-style expressions only 
 74          self.path = [] 
 75          self.tag = None 
 76          if tokens and tokens[0][0] == "/": 
 77              raise SyntaxError("cannot use absolute path on element") 
 78          while tokens: 
 79              op, tag = tokens.pop(0) 
 80              if tag or op == "*": 
 81                  self.path.append(tag or op) 
 82              elif op == ".": 
 83                  pass 
 84              elif op == "/": 
 85                  self.path.append(xpath_descendant_or_self()) 
 86                  continue 
 87              else: 
 88                  raise SyntaxError("unsupported path syntax (%s)" % op) 
 89              if tokens: 
 90                  op, tag = tokens.pop(0) 
 91                  if op != "/": 
 92                      raise SyntaxError( 
 93                          "expected path separator (%s)" % (op or tag) 
 94                          ) 
 95          if self.path and isinstance(self.path[-1], xpath_descendant_or_self): 
 96              raise SyntaxError("path cannot end with //") 
 97          if len(self.path) == 1 and isinstance(self.path[0], type("")): 
 98              self.tag = self.path[0] 
 99   
100      ## 
101      # Find first matching object. 
102   
103 -    def find(self, element): 
104          tag = self.tag 
105          if tag is None: 
106              nodeset = self.findall(element) 
107              if not nodeset: 
108                  return None 
109              return nodeset[0] 
110          for elem in element: 
111              if elem.tag == tag: 
112                  return elem 
113          return None 
114   
115      ## 
116      # Find text for first matching object. 
117   
118 -    def findtext(self, element, default=None): 
119          tag = self.tag 
120          if tag is None: 
121              nodeset = self.findall(element) 
122              if not nodeset: 
123                  return default 
124              return nodeset[0].text or "" 
125          for elem in element: 
126              if elem.tag == tag: 
127                  return elem.text or "" 
128          return default 
129   
130      ## 
131      # Find all matching objects. 
132   
133 -    def findall(self, element): 
134          nodeset = [element] 
135          index = 0 
136          while 1: 
137              try: 
138                  path = self.path[index] 
139                  index = index + 1 
140              except IndexError: 
141                  return nodeset 
142              set = [] 
143              if isinstance(path, xpath_descendant_or_self): 
144                  try: 
145                      tag = self.path[index] 
146                      if not isinstance(tag, type("")): 
147                          tag = None 
148                      else: 
149                          index = index + 1 
150                  except IndexError: 
151                      tag = None # invalid path 
152                  for node in nodeset: 
153                      new = list(node.getiterator(tag)) 
154                      if new and new[0] is node: 
155                          set.extend(new[1:]) 
156                      else: 
157                          set.extend(new) 
158              else: 
159                  for node in nodeset: 
160                      for node in node: 
161                          if path == "*" or node.tag == path: 
162                              set.append(node) 
163              if not set: 
164                  return [] 
165              nodeset = set 
166   
167  _cache = {} 
168   
169  ## 
170  # (Internal) Compile path. 
171   
172 -def _compile(path): 
173      p = _cache.get(path) 
174      if p is not None: 
175          return p 
176      p = Path(path) 
177      if len(_cache) >= 100: 
178          _cache.clear() 
179      _cache[path] = p 
180      return p 
181   
182  ## 
183  # Find first matching object. 
184   
185 -def find(element, path): 
186      return _compile(path).find(element) 
187   
188  ## 
189  # Find text for first matching object. 
190   
191 -def findtext(element, path, default=None): 
192      return _compile(path).findtext(element, default) 
193   
194  ## 
195  # Find all matching objects. 
196   
197 -def findall(element, path): 
198      return _compile(path).findall(element) 
199