"Element.findall()" and fully-consumed "Element.iterfind()" exhibit "O(n^2)" time complexity when using XPath index predicates (e.g. "[1]", "[last()]", "[last()-N]") on XML documents with many same-tag siblings. "Element.find()" is only affected when the first match is near the end  of the sibling list, such as with "[last()]" or "[last()-N]";  ".//item[1]" short-circuits after the first match.