Class PythonElementClassLookup

            object --+        
                     |        
    ElementClassLookup --+    
                         |    
FallbackElementClassLookup --+
                             |
                            PythonElementClassLookup

PythonElementClassLookup(self, fallback=None) Element class lookup based on a subclass method.

This class lookup scheme allows access to the entire XML tree in read-only mode. To use it, re-implement the lookup(self, doc, root) method in a subclass:

from lxml import etree, pyclasslookup

class MyElementClass(etree.ElementBase):
    honkey = True

class MyLookup(pyclasslookup.PythonElementClassLookup):
    def lookup(self, doc, root):
        if root.tag == "sometag":
            return MyElementClass
        else:
            for child in root:
                if child.tag == "someothertag":
                    return MyElementClass
        # delegate to default
        return None

If you return None from this method, the fallback will be called.

The first argument is the opaque document instance that contains the Element. The second argument is a lightweight Element proxy implementation that is only valid during the lookup. Do not try to keep a reference to it. Once the lookup is done, the proxy will be invalid.

Also, you cannot wrap such a read-only Element in an ElementTree, and you must take care not to keep a reference to them outside of the lookup() method.

Note that the API of the Element objects is not complete. It is purely read-only and does not support all features of the normal lxml.etree API (such as XPath, extended slicing or some iteration methods).

See http://codespeak.net/lxml/element_classes.html