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  """
     37  The ``E`` Element factory for generating XML documents.
     38  """
     39
     40  import 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
     50 -class ElementMaker(object):
     51      """Element generator factory.
     52
     53      Unlike the ordinary Element factory, the E factory allows you to pass in
     54      more than just a tag and some optional attributes; you can also pass in
     55      text and other elements.  The text is added as either text or tail
     56      attributes, and elements are inserted at the right spot.  Some small
     57      examples::
     58
     59          >>> from lxml import etree as ET
     60          >>> from lxml.builder import E
     61
     62          >>> ET.tostring(E("tag"))
     63          '<tag/>'
     64          >>> ET.tostring(E("tag", "text"))
     65          '<tag>text</tag>'
     66          >>> ET.tostring(E("tag", "text", key="value"))
     67          '<tag key="value">text</tag>'
     68          >>> ET.tostring(E("tag", E("subtag", "text"), "tail"))
     69          '<tag><subtag>text</subtag>tail</tag>'
     70
     71      For simple tags, the factory also allows you to write ``E.tag(...)`` instead
     72      of ``E('tag', ...)``::
     73
     74          >>> ET.tostring(E.tag())
     75          '<tag/>'
     76          >>> ET.tostring(E.tag("text"))
     77          '<tag>text</tag>'
     78          >>> ET.tostring(E.tag(E.subtag("text"), "tail"))
     79          '<tag><subtag>text</subtag>tail</tag>'
     80
     81      Here's a somewhat larger example; this shows how to generate HTML
     82      documents, using a mix of prepared factory functions for inline elements,
     83      nested ``E.tag`` calls, and embedded XHTML fragments::
     84
     85          # some common inline elements
     86          A = E.a
     87          I = E.i
     88          B = E.b
     89
     90          def CLASS(v):
     91              # helper function, 'class' is a reserved word
     92              return {'class': v}
     93
     94          page = (
     95              E.html(
     96                  E.head(
     97                      E.title("This is a sample document")
     98                  ),
     99                  E.body(
    100                      E.h1("Hello!", CLASS("title")),
    101                      E.p("This is a paragraph with ", B("bold"), " text in it!"),
    102                      E.p("This is another paragraph, with a ",
    103                          A("link", href="http://www.python.org"), "."),
    104                      E.p("Here are some reservered characters: <spam&egg>."),
    105                      ET.XML("<p>And finally, here is an embedded XHTML fragment.</p>"),
    106                  )
    107              )
    108          )
    109
    110          print ET.tostring(page)
    111
    112      Here's a prettyprinted version of the output from the above script::
    113
    114          <html>
    115            <head>
    116              <title>This is a sample document</title>
    117            </head>
    118            <body>
    119              <h1 class="title">Hello!</h1>
    120              <p>This is a paragraph with <b>bold</b> text in it!</p>
    121              <p>This is another paragraph, with <a href="http://www.python.org">link</a>.</p>
    122              <p>Here are some reservered characters: &lt;spam&amp;egg&gt;.</p>
    123              <p>And finally, here is an embedded XHTML fragment.</p>
    124            </body>
    125          </html>
    126      """
    127
    128 -    def __init__(self, typemap=None,
    129                   namespace=None, nsmap=None, makeelement=None):
    130          if namespace is not None:
    131              self._namespace = '{' + namespace + '}'
    132          else:
    133              self._namespace = None
    134
    135          if nsmap:
    136              self._nsmap = dict(nsmap)
    137          else:
    138              self._nsmap = None
    139
    140          if makeelement is not None:
    141              assert callable(makeelement)
    142              self._makeelement = makeelement
    143          else:
    144              self._makeelement = ET.Element
    145
    146          # initialize type map for this element factory
    147
    148          if typemap:
    149              typemap = typemap.copy()
    150          else:
    151              typemap = {}
    152
    153          def add_text(elem, item):
    154              if len(elem):
    155                  elem[-1].tail = (elem[-1].tail or "") + item
    156              else:
    157                  elem.text = (elem.text or "") + item
    158          if str not in typemap:
    159              typemap[str] = add_text
    160          if unicode not in typemap:
    161              typemap[unicode] = add_text
    162
    163          def add_dict(elem, item):
    164              attrib = elem.attrib
    165              for k, v in item.items():
    166                  if isinstance(v, basestring):
    167                      attrib[k] = v
    168                  else:
    169                      attrib[k] = typemap[type(v)](None, v)
    170          if dict not in typemap:
    171              typemap[dict] = add_dict
    172
    173          self._typemap = typemap
    174
    175 -    def __call__(self, tag, *children, **attrib):
    176          get = self._typemap.get
    177
    178          if self._namespace is not None and tag[0] != '{':
    179              tag = self._namespace + tag
    180          elem = self._makeelement(tag, nsmap=self._nsmap)
    181          if attrib:
    182              get(dict)(elem, attrib)
    183
    184          for item in children:
    185              if callable(item):
    186                  item = item()
    187              t = get(type(item))
    188              if t is None:
    189                  if ET.iselement(item):
    190                      elem.append(item)
    191                      continue
    192                  raise TypeError("bad argument type: %r" % item)
    193              else:
    194                  v = t(elem, item)
    195                  if v:
    196                      get(type(v))(elem, v)
    197
    198          return elem
    199
    200 -    def __getattr__(self, tag):
    201          return partial(self, tag)
    202
    203  # create factory object
    204  E = ElementMaker()
    205