Source Code for Module lxml.builder

  1  # 
  2  # Element generator factory by Fredrik Lundh. 
  3  # 
  4  # Source: 
  5  #    http://online.effbot.org/2006_11_01_archive.htm#et-builder 
  6  #    http://effbot.python-hosting.com/file/stuff/sandbox/elementlib/builder.py 
  7  # 
  8  # -------------------------------------------------------------------- 
  9  # The ElementTree toolkit is 
 10  # 
 11  # Copyright (c) 1999-2004 by Fredrik Lundh 
 12  # 
 13  # By obtaining, using, and/or copying this software and/or its 
 14  # associated documentation, you agree that you have read, understood, 
 15  # and will comply with the following terms and conditions: 
 16  # 
 17  # Permission to use, copy, modify, and distribute this software and 
 18  # its associated documentation for any purpose and without fee is 
 19  # hereby granted, provided that the above copyright notice appears in 
 20  # all copies, and that both that copyright notice and this permission 
 21  # notice appear in supporting documentation, and that the name of 
 22  # Secret Labs AB or the author not be used in advertising or publicity 
 23  # pertaining to distribution of the software without specific, written 
 24  # prior permission. 
 25  # 
 26  # SECRET LABS AB AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD 
 27  # TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANT- 
 28  # ABILITY AND FITNESS.  IN NO EVENT SHALL SECRET LABS AB OR THE AUTHOR 
 29  # BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY 
 30  # DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, 
 31  # WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS 
 32  # ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE 
 33  # OF THIS SOFTWARE. 
 34  # -------------------------------------------------------------------- 
 35   
 36  """ 
 37  The ``E`` Element factory for generating XML documents. 
 38  """ 
 39   
 40  import lxml.etree as ET 
 41   
 42  try: 
 43      from functools import partial 
 44  except ImportError: 
 45      # fake it for pre-2.5 releases 
 46 -    def partial(func, tag): 
 47          return lambda *args, **kwargs: func(tag, *args, **kwargs) 
 48   
 49  try: 
 50      callable 
 51  except NameError: 
 52      # Python 3 
 53 -    def callable(f): 
 54          return hasattr(f, '__call__') 
 55   
 56  try: 
 57      basestring 
 58  except NameError: 
 59      basestring = str 
 60   
 61  try: 
 62      unicode 
 63  except NameError: 
 64      unicode = str 
 65   
 66   
 67 -class ElementMaker(object): 
 68      """Element generator factory. 
 69   
 70      Unlike the ordinary Element factory, the E factory allows you to pass in 
 71      more than just a tag and some optional attributes; you can also pass in 
 72      text and other elements.  The text is added as either text or tail 
 73      attributes, and elements are inserted at the right spot.  Some small 
 74      examples:: 
 75   
 76          >>> from lxml import etree as ET 
 77          >>> from lxml.builder import E 
 78   
 79          >>> ET.tostring(E("tag")) 
 80          '<tag/>' 
 81          >>> ET.tostring(E("tag", "text")) 
 82          '<tag>text</tag>' 
 83          >>> ET.tostring(E("tag", "text", key="value")) 
 84          '<tag key="value">text</tag>' 
 85          >>> ET.tostring(E("tag", E("subtag", "text"), "tail")) 
 86          '<tag><subtag>text</subtag>tail</tag>' 
 87   
 88      For simple tags, the factory also allows you to write ``E.tag(...)`` instead 
 89      of ``E('tag', ...)``:: 
 90   
 91          >>> ET.tostring(E.tag()) 
 92          '<tag/>' 
 93          >>> ET.tostring(E.tag("text")) 
 94          '<tag>text</tag>' 
 95          >>> ET.tostring(E.tag(E.subtag("text"), "tail")) 
 96          '<tag><subtag>text</subtag>tail</tag>' 
 97   
 98      Here's a somewhat larger example; this shows how to generate HTML 
 99      documents, using a mix of prepared factory functions for inline elements, 
100      nested ``E.tag`` calls, and embedded XHTML fragments:: 
101   
102          # some common inline elements 
103          A = E.a 
104          I = E.i 
105          B = E.b 
106   
107          def CLASS(v): 
108              # helper function, 'class' is a reserved word 
109              return {'class': v} 
110   
111          page = ( 
112              E.html( 
113                  E.head( 
114                      E.title("This is a sample document") 
115                  ), 
116                  E.body( 
117                      E.h1("Hello!", CLASS("title")), 
118                      E.p("This is a paragraph with ", B("bold"), " text in it!"), 
119                      E.p("This is another paragraph, with a ", 
120                          A("link", href="http://www.python.org"), "."), 
121                      E.p("Here are some reservered characters: <spam&egg>."), 
122                      ET.XML("<p>And finally, here is an embedded XHTML fragment.</p>"), 
123                  ) 
124              ) 
125          ) 
126   
127          print ET.tostring(page) 
128   
129      Here's a prettyprinted version of the output from the above script:: 
130   
131          <html> 
132            <head> 
133              <title>This is a sample document</title> 
134            </head> 
135            <body> 
136              <h1 class="title">Hello!</h1> 
137              <p>This is a paragraph with <b>bold</b> text in it!</p> 
138              <p>This is another paragraph, with <a href="http://www.python.org">link</a>.</p> 
139              <p>Here are some reservered characters: &lt;spam&amp;egg&gt;.</p> 
140              <p>And finally, here is an embedded XHTML fragment.</p> 
141            </body> 
142          </html> 
143   
144      For namespace support, you can pass a namespace map (``nsmap``) 
145      and/or a specific target ``namespace`` to the ElementMaker class:: 
146   
147          >>> E = ElementMaker(namespace="http://my.ns/") 
148          >>> print(ET.tostring( E.test )) 
149          <test xmlns="http://my.ns/"/> 
150   
151          >>> E = ElementMaker(namespace="http://my.ns/", nsmap={'p':'http://my.ns/'}) 
152          >>> print(ET.tostring( E.test )) 
153          <p:test xmlns:p="http://my.ns/"/> 
154      """ 
155   
156 -    def __init__(self, typemap=None, 
157                   namespace=None, nsmap=None, makeelement=None): 
158          if namespace is not None: 
159              self._namespace = '{' + namespace + '}' 
160          else: 
161              self._namespace = None 
162   
163          if nsmap: 
164              self._nsmap = dict(nsmap) 
165          else: 
166              self._nsmap = None 
167   
168          if makeelement is not None: 
169              assert callable(makeelement) 
170              self._makeelement = makeelement 
171          else: 
172              self._makeelement = ET.Element 
173   
174          # initialize type map for this element factory 
175   
176          if typemap: 
177              typemap = typemap.copy() 
178          else: 
179              typemap = {} 
180           
181          def add_text(elem, item): 
182              try: 
183                  elem[-1].tail = (elem[-1].tail or "") + item 
184              except IndexError: 
185                  elem.text = (elem.text or "") + item 
186          if str not in typemap: 
187              typemap[str] = add_text 
188          if unicode not in typemap: 
189              typemap[unicode] = add_text 
190   
191          def add_dict(elem, item): 
192              attrib = elem.attrib 
193              for k, v in item.items(): 
194                  if isinstance(v, basestring): 
195                      attrib[k] = v 
196                  else: 
197                      attrib[k] = typemap[type(v)](None, v) 
198          if dict not in typemap: 
199              typemap[dict] = add_dict 
200   
201          self._typemap = typemap 
202   
203 -    def __call__(self, tag, *children, **attrib): 
204          get = self._typemap.get 
205   
206          if self._namespace is not None and tag[0] != '{': 
207              tag = self._namespace + tag 
208          elem = self._makeelement(tag, nsmap=self._nsmap) 
209          if attrib: 
210              get(dict)(elem, attrib) 
211   
212          for item in children: 
213              if callable(item): 
214                  item = item() 
215              t = get(type(item)) 
216              if t is None: 
217                  if ET.iselement(item): 
218                      elem.append(item) 
219                      continue 
220                  for basetype in type(item).__mro__: 
221                      # See if the typemap knows of any of this type's bases. 
222                      t = get(basetype) 
223                      if t is not None: 
224                          break 
225                  else: 
226                      raise TypeError("bad argument type: %s(%r)" % 
227                                      (type(item).__name__, item)) 
228              v = t(elem, item) 
229              if v: 
230                  get(type(v))(elem, v) 
231   
232          return elem 
233   
234 -    def __getattr__(self, tag): 
235          return partial(self, tag) 
236   
237  # create factory object 
238  E = ElementMaker() 
239