How to retrieve all values of a specific attribute from sub-elements that contain this attribute?

Question

I have the following XML file:

<main>
  <node>
    <party iot="00">Big</party>
    <children type="me" value="3" iot="A">
       <p>
          <display iot="B|S">
             <figure iot="FF"/>
          </display>
       </p>
       <li iot="C"/>
       <ul/>
    </children>
  </node>
  <node>
    <party iot="01">Small</party>
    <children type="me" value="1" iot="N">
       <p>
          <display iot="T|F">
             <figure iot="MM"/>
          </display>
       </p>
    </children>
  </node>
</main>

How can I retrieve all values of iot attribute from sub-elements of children of the first node? I need to retrieve the values of iot as a list.

The expected result:

iot_list = ['A','B|S','FF','C']

This is my current code:

import xml.etree.ElementTree as ET

mytree = ET.parse("file.xml")
myroot = mytree.getroot()
list_nodes = myroot.findall('node')
for n in list_nodes:
   # ???

This is not well-informed XML: `
`. Assuming it is typo, consider fixing here in post. If not, check its source. Avoid [building XML with string concatenation](https://stackoverflow.com/questions/3034611/whats-so-bad-about-building-xml-with-string-concatenation). — Parfait, Apr 19 '22 at 00:06
Consider Python's 3rd party, `lxml`, that supports the full XPath 1.0 and can easily return all iot attributes of children's descendants: `descendant::*/@iot`. — Parfait, Apr 19 '22 at 00:11
@Parfait: Thanks, yes, this was typo. Thanks for noticing. I've just fixed it. — Fluxy, Apr 21 '22 at 08:34
The `` element (in both ``s doesn't have any children; `
` and `
@JackFleeting I see what you mean. I've just updated the example. Thanks. — Fluxy, Apr 22 '22 at 10:41
That's better! Also - it seems you don't only want to "retrieve all values of iot attribute from **sub-elements** of children" but also from the `` element itself (`A`); correct? — Jack Fleeting, Apr 22 '22 at 12:19

score 1 · Accepted Answer · answered Apr 24 '22 at 13:05

1

This is easier to do using the lxml library:

If the sample xml in your question represents the exact structure of the actual xml:

from lxml import etree
data = """[your xml above]"""
doc = etree.XML(data)

print(doc.xpath('//node[1]//*[not(self::party)][@iot]/@iot'))

More generically:

for t in doc.xpath('//node[1]//children'):
    print(t.xpath('.//descendant-or-self::*/@iot'))

In either case, the output should be

['A', 'B|S', 'FF', 'C']

answered Apr 24 '22 at 13:05

Jack Fleeting

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If you know a similar solution using `xml.etree.ElementTree`, I'd appreciate. – Fluxy Apr 27 '22 at 15:03
1

@Fluxy - I doubt it (xpath support in ElementTree is much weaker than that of lxml), but I'll take a look. – Jack Fleeting Apr 27 '22 at 15:07

How to retrieve all values of a specific attribute from sub-elements that contain this attribute?

1 Answers1