使用lxml etree直接访问元素和属性

Question

Given the following xml structure:

<root>
    <a>
        <from name="abc">
            <b>xxx</b>
            <c>yyy</c>
        </from>
        <to name="def">
            <b>blah blah</b>
            <c>another blah blah</c>
        </to>
    </a>
</root>

How can I access directly the value of "from.b" of each "a" without loading first "from" (with find()) of each "a"?

As you can see there are exactly the same elements under "from" and "to". So the method findall() would not work as I have to differentiate where the value of "b" is coming from.

I would like to get the method of direct access because if I have to load each child element (there is a lot) my code would be quite verbose. And in addition in my case performance counts and I have a lot of XML docs to parse! So I have to find the fastest method to go through the document (and store the data into a DB)

Within each "a" element there is exactly 1 "from" element and within each "from" element there is exactly 1 "b" element.

I have no problem to do this with lxml objectify, but I want to use etree because first I have to parse the XML document with etree because I have to validate first the xml schema against an XSD doc and I do not want to reparse the whole document again.

Answer 1

find (and findall ) lets you specify a path to elements as well, for example you can do:

root = ET.fromstring(input_xml)

for a in root.findall('a'):
    print(a, a.find('from/b').text)

assuming you do always have exactly one from and b element.

otherwise, I might be tempted to use findall and do checks in Python code if this is designed to be more robust