Speedup setting attributes on etree impleemntations

Author: gsnedders

html5lib/treebuilders/etree.py

@@ -61,16 +61,17 @@ def _getAttributes(self):
             return self._element.attrib
 
         def _setAttributes(self, attributes):
-            # Delete existing attributes first
-            # XXX - there may be a better way to do this...
-            for key in list(self._element.attrib.keys()):
-                del self._element.attrib[key]
-            for key, value in attributes.items():
-                if isinstance(key, tuple):
-                    name = "{%s}%s" % (key[2], key[1])
-                else:
-                    name = key
-                self._element.set(name, value)
+            el_attrib = self._element.attrib
+            el_attrib.clear()
+            if attributes:
+                # calling .items _always_ allocates, and the above truthy check is cheaper than the
+                # allocation on average
+                for key, value in attributes.items():
+                    if isinstance(key, tuple):
+                        name = "{%s}%s" % (key[2], key[1])
+                    else:
+                        name = key
+                    el_attrib[name] = value
 
         attributes = property(_getAttributes, _setAttributes)
 
@@ -129,8 +130,10 @@ def insertText(self, data, insertBefore=None):
 
         def cloneNode(self):
             element = type(self)(self.name, self.namespace)
-            for name, value in self.attributes.items():
-                element.attributes[name] = value
+            try:
+                element._element.attrib = self._element.attrib.copy()
+            except AttributeError:
+                element.attributes = self.attributes
             return element
 
         def reparentChildren(self, newParent):