doc/html/api/lxml.etree.PythonElementClassLookup-class.html

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  47         Class&nbsp;PythonElementClassLookup
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  63 <!-- ==================== CLASS DESCRIPTION ==================== -->
  64 <h1 class="epydoc">Class PythonElementClassLookup</h1><p class="nomargin-top"></p>
  65 <pre class="base-tree">
  66             object --+
  67                      |
  68     <a href="lxml.etree.ElementClassLookup-class.html">ElementClassLookup</a> --+
  69                          |
  70 <a href="lxml.etree.FallbackElementClassLookup-class.html">FallbackElementClassLookup</a> --+
  71                              |
  72                             <strong class="uidshort">PythonElementClassLookup</strong>
  73 </pre>
  74
  75 <hr />
  76 <p>PythonElementClassLookup(self, fallback=None)
  77 Element class lookup based on a subclass method.</p>
  78 <p>This class lookup scheme allows access to the entire XML tree in
  79 read-only mode.  To use it, re-implement the <tt class="rst-docutils literal">lookup(self, doc,
  80 root)</tt> method in a subclass:</p>
  81 <pre class="rst-literal-block">
  82 from lxml import etree, pyclasslookup
  83
  84 class MyElementClass(etree.ElementBase):
  85     honkey = True
  86
  87 class MyLookup(pyclasslookup.PythonElementClassLookup):
  88     def lookup(self, doc, root):
  89         if root.tag == &quot;sometag&quot;:
  90             return MyElementClass
  91         else:
  92             for child in root:
  93                 if child.tag == &quot;someothertag&quot;:
  94                     return MyElementClass
  95         # delegate to default
  96         return None
  97 </pre>
  98 <p>If you return None from this method, the fallback will be called.</p>
  99 <p>The first argument is the opaque document instance that contains
 100 the Element.  The second argument is a lightweight Element proxy
 101 implementation that is only valid during the lookup.  Do not try
 102 to keep a reference to it.  Once the lookup is done, the proxy
 103 will be invalid.</p>
 104 <p>Also, you cannot wrap such a read-only Element in an ElementTree,
 105 and you must take care not to keep a reference to them outside of
 106 the <a href="lxml.etree.PythonElementClassLookup-class.html#lookup" class="link">lookup()</a> method.</p>
 107 <p>Note that the API of the Element objects is not complete.  It is
 108 purely read-only and does not support all features of the normal
 109 <a href="lxml.etree-module.html" class="link">lxml.etree</a> API (such as XPath, extended slicing or some
 110 iteration methods).</p>
 111 <p>See <a class="rst-reference external" href="http://codespeak.net/lxml/element_classes.html" target="_top">http://codespeak.net/lxml/element_classes.html</a></p>
 112
 113 <!-- ==================== INSTANCE METHODS ==================== -->
 114 <a name="section-InstanceMethods"></a>
 115 <table class="summary" border="1" cellpadding="3"
 116        cellspacing="0" width="100%" bgcolor="white">
 117 <tr bgcolor="#70b0f0" class="table-header">
 118   <td colspan="2" class="table-header">
 119     <table border="0" cellpadding="0" cellspacing="0" width="100%">
 120       <tr valign="top">
 121         <td align="left"><span class="table-header">Instance Methods</span></td>
 122         <td align="right" valign="top"
 123          ><span class="options">[<a href="#section-InstanceMethods"
 124          class="privatelink" onclick="toggle_private();"
 125          >hide private</a>]</span></td>
 126       </tr>
 127     </table>
 128   </td>
 129 </tr>
 130 <tr>
 131     <td width="15%" align="right" valign="top" class="summary">
 132       <span class="summary-type">a new object with type S, a subtype of T</span>
 133     </td><td class="summary">
 134       <table width="100%" cellpadding="0" cellspacing="0" border="0">
 135         <tr>
 136           <td><span class="summary-sig"><a href="lxml.etree.PythonElementClassLookup-class.html#__new__" class="summary-sig-name">__new__</a>(<span class="summary-sig-arg">T</span>,
 137         <span class="summary-sig-arg">S</span>,
 138         <span class="summary-sig-arg">...</span>)</span></td>
 139           <td align="right" valign="top">
 140
 141
 142           </td>
 143         </tr>
 144       </table>
 145
 146     </td>
 147   </tr>
 148 <tr>
 149     <td width="15%" align="right" valign="top" class="summary">
 150       <span class="summary-type">&nbsp;</span>
 151     </td><td class="summary">
 152       <table width="100%" cellpadding="0" cellspacing="0" border="0">
 153         <tr>
 154           <td><span class="summary-sig"><a name="lookup"></a><span class="summary-sig-name">lookup</span>(<span class="summary-sig-arg">self</span>,
 155         <span class="summary-sig-arg">doc</span>,
 156         <span class="summary-sig-arg">element</span>)</span><br />
 157       Override this method to implement your own lookup scheme.</td>
 158           <td align="right" valign="top">
 159
 160
 161           </td>
 162         </tr>
 163       </table>
 164
 165     </td>
 166   </tr>
 167   <tr>
 168     <td colspan="2" class="summary">
 169     <p class="indent-wrapped-lines"><b>Inherited from <code><a href="lxml.etree.FallbackElementClassLookup-class.html">FallbackElementClassLookup</a></code></b>:
 170       <code><a href="lxml.etree.FallbackElementClassLookup-class.html#__init__">__init__</a></code>,
 171       <code><a href="lxml.etree.FallbackElementClassLookup-class.html#set_fallback">set_fallback</a></code>
 172       </p>
 173     <p class="indent-wrapped-lines"><b>Inherited from <code>object</code></b>:
 174       <code>__delattr__</code>,
 175       <code>__format__</code>,
 176       <code>__getattribute__</code>,
 177       <code>__hash__</code>,
 178       <code>__reduce__</code>,
 179       <code>__reduce_ex__</code>,
 180       <code>__repr__</code>,
 181       <code>__setattr__</code>,
 182       <code>__sizeof__</code>,
 183       <code>__str__</code>,
 184       <code>__subclasshook__</code>
 185       </p>
 186     </td>
 187   </tr>
 188 </table>
 189 <!-- ==================== PROPERTIES ==================== -->
 190 <a name="section-Properties"></a>
 191 <table class="summary" border="1" cellpadding="3"
 192        cellspacing="0" width="100%" bgcolor="white">
 193 <tr bgcolor="#70b0f0" class="table-header">
 194   <td colspan="2" class="table-header">
 195     <table border="0" cellpadding="0" cellspacing="0" width="100%">
 196       <tr valign="top">
 197         <td align="left"><span class="table-header">Properties</span></td>
 198         <td align="right" valign="top"
 199          ><span class="options">[<a href="#section-Properties"
 200          class="privatelink" onclick="toggle_private();"
 201          >hide private</a>]</span></td>
 202       </tr>
 203     </table>
 204   </td>
 205 </tr>
 206   <tr>
 207     <td colspan="2" class="summary">
 208     <p class="indent-wrapped-lines"><b>Inherited from <code><a href="lxml.etree.FallbackElementClassLookup-class.html">FallbackElementClassLookup</a></code></b>:
 209       <code><a href="lxml.etree.FallbackElementClassLookup-class.html#fallback">fallback</a></code>
 210       </p>
 211     <p class="indent-wrapped-lines"><b>Inherited from <code>object</code></b>:
 212       <code>__class__</code>
 213       </p>
 214     </td>
 215   </tr>
 216 </table>
 217 <!-- ==================== METHOD DETAILS ==================== -->
 218 <a name="section-MethodDetails"></a>
 219 <table class="details" border="1" cellpadding="3"
 220        cellspacing="0" width="100%" bgcolor="white">
 221 <tr bgcolor="#70b0f0" class="table-header">
 222   <td colspan="2" class="table-header">
 223     <table border="0" cellpadding="0" cellspacing="0" width="100%">
 224       <tr valign="top">
 225         <td align="left"><span class="table-header">Method Details</span></td>
 226         <td align="right" valign="top"
 227          ><span class="options">[<a href="#section-MethodDetails"
 228          class="privatelink" onclick="toggle_private();"
 229          >hide private</a>]</span></td>
 230       </tr>
 231     </table>
 232   </td>
 233 </tr>
 234 </table>
 235 <a name="__new__"></a>
 236 <div>
 237 <table class="details" border="1" cellpadding="3"
 238        cellspacing="0" width="100%" bgcolor="white">
 239 <tr><td>
 240   <table width="100%" cellpadding="0" cellspacing="0" border="0">
 241   <tr valign="top"><td>
 242   <h3 class="epydoc"><span class="sig"><span class="sig-name">__new__</span>(<span class="sig-arg">T</span>,
 243         <span class="sig-arg">S</span>,
 244         <span class="sig-arg">...</span>)</span>
 245   </h3>
 246   </td><td align="right" valign="top"
 247     >&nbsp;
 248     </td>
 249   </tr></table>
 250
 251
 252   <dl class="fields">
 253     <dt>Returns: a new object with type S, a subtype of T</dt>
 254     <dt>Overrides:
 255         object.__new__
 256     </dt>
 257   </dl>
 258 </td></tr></table>
 259 </div>
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