Why doesn findall() support full XPath expressions?
It was decided that it is more important to keep compatibility with ElementTree to simplify code migration between the libraries. The main difference compared to XPath is the {namespace}tagname notation used in findall(), which is not valid XPath. ElementTree and lxml.etree use the same implementation, which assures 100% compatibility. Note that findall() is so fast in lxml that a native implementation would not bring any performance benefits.
