python lxml how to find multiple markup? -

i know if want find a nodes can use root.xpath('.//a'). how should if want iterate on a or b nodes (depth first search)?

<?xml version="1.0"?> <root>     <x><a>one</a></x>     <x><x><b>three</b></x></x>     <b>three</b> </root>  

there possible ways, here of them.

using union operator (|) :

.//a | .//b 

using or operator allow multiple possible self::element, mentioned in comment :

.//*[self::a or self::b] 

or mix of 2 :

.//*[self::a | self::b]