Package lxml :: Module builder

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# 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  import etree as ET
     37
     38  try:
     39      from functools import partial
     40  except ImportError:
     41      # fake it for pre-2.5 releases
     42 -    def partial(func, tag):
     43          return lambda *args, **kwargs: func(tag, *args, **kwargs)
     44
     45
     46 -class ElementMaker(object):
     47      """Element generator factory.
     48
     49      Unlike the ordinary Element factory, the E factory allows you to pass in
     50      more than just a tag and some optional attributes; you can also pass in
     51      text and other elements.  The text is added as either text or tail
     52      attributes, and elements are inserted at the right spot.  Some small
     53      examples::
     54
     55          >>> from lxml import etree as ET
     56          >>> from lxml.builder import E
     57
     58          >>> ET.tostring(E("tag"))
     59          '<tag/>'
     60          >>> ET.tostring(E("tag", "text"))
     61          '<tag>text</tag>'
     62          >>> ET.tostring(E("tag", "text", key="value"))
     63          '<tag key="value">text</tag>'
     64          >>> ET.tostring(E("tag", E("subtag", "text"), "tail"))
     65          '<tag><subtag>text</subtag>tail</tag>'
     66
     67      For simple tags, the factory also allows you to write ``E.tag(...)`` instead
     68      of ``E('tag', ...)``::
     69
     70          >>> ET.tostring(E.tag())
     71          '<tag/>'
     72          >>> ET.tostring(E.tag("text"))
     73          '<tag>text</tag>'
     74          >>> ET.tostring(E.tag(E.subtag("text"), "tail"))
     75          '<tag><subtag>text</subtag>tail</tag>'
     76
     77      Here's a somewhat larger example; this shows how to generate HTML
     78      documents, using a mix of prepared factory functions for inline elements,
     79      nested ``E.tag`` calls, and embedded XHTML fragments::
     80
     81          # some common inline elements
     82          A = E.a
     83          I = E.i
     84          B = E.b
     85
     86          def CLASS(v):
     87              # helper function, 'class' is a reserved word
     88              return {'class': v}
     89
     90          page = (
     91              E.html(
     92                  E.head(
     93                      E.title("This is a sample document")
     94                  ),
     95                  E.body(
     96                      E.h1("Hello!", CLASS("title")),
     97                      E.p("This is a paragraph with ", B("bold"), " text in it!"),
     98                      E.p("This is another paragraph, with a ",
     99                          A("link", href="http://www.python.org"), "."),
    100                      E.p("Here are some reservered characters: <spam&egg>."),
    101                      ET.XML("<p>And finally, here is an embedded XHTML fragment.</p>"),
    102                  )
    103              )
    104          )
    105
    106          print ET.tostring(page)
    107
    108      Here's a prettyprinted version of the output from the above script::
    109
    110          <html>
    111            <head>
    112              <title>This is a sample document</title>
    113            </head>
    114            <body>
    115              <h1 class="title">Hello!</h1>
    116              <p>This is a paragraph with <b>bold</b> text in it!</p>
    117              <p>This is another paragraph, with <a href="http://www.python.org">link</a>.</p>
    118              <p>Here are some reservered characters: &lt;spam&amp;egg&gt;.</p>
    119              <p>And finally, here is an embedded XHTML fragment.</p>
    120            </body>
    121          </html>
    122      """
    123
    124 -    def __init__(self, typemap=None,
    125                   namespace=None, nsmap=None, makeelement=None):
    126          if namespace is not None:
    127              self._namespace = '{' + namespace + '}'
    128          else:
    129              self._namespace = None
    130
    131          if nsmap:
    132              self._nsmap = dict(nsmap)
    133          else:
    134              self._nsmap = None
    135
    136          if makeelement is not None:
    137              assert callable(makeelement)
    138              self._makeelement = makeelement
    139          else:
    140              self._makeelement = ET.Element
    141
    142          # initialize type map for this element factory
    143
    144          if typemap:
    145              typemap = typemap.copy()
    146          else:
    147              typemap = {}
    148
    149          def add_text(elem, item):
    150              if len(elem):
    151                  elem[-1].tail = (elem[-1].tail or "") + item
    152              else:
    153                  elem.text = (elem.text or "") + item
    154          if str not in typemap:
    155              typemap[str] = add_text
    156          if unicode not in typemap:
    157              typemap[unicode] = add_text
    158
    159          def add_dict(elem, item):
    160              attrib = elem.attrib
    161              for k, v in item.items():
    162                  if isinstance(v, basestring):
    163                      attrib[k] = v
    164                  else:
    165                      attrib[k] = typemap[type(v)](None, v)
    166          if dict not in typemap:
    167              typemap[dict] = add_dict
    168
    169          self._typemap = typemap
    170
    171 -    def __call__(self, tag, *children, **attrib):
    172          get = self._typemap.get
    173
    174          if self._namespace is not None and tag[0] != '{':
    175              tag = self._namespace + tag
    176          elem = self._makeelement(tag, nsmap=self._nsmap)
    177          if attrib:
    178              get(dict)(elem, attrib)
    179
    180          for item in children:
    181              if callable(item):
    182                  item = item()
    183              t = get(type(item))
    184              if t is None:
    185                  if ET.iselement(item):
    186                      elem.append(item)
    187                      continue
    188                  raise TypeError("bad argument type: %r" % item)
    189              else:
    190                  v = t(elem, item)
    191                  if v:
    192                      get(type(v))(elem, v)
    193
    194          return elem
    195
    196 -    def __getattr__(self, tag):
    197          return partial(self, tag)
    198
    199  # create factory object
    200  E = ElementMaker()
    201