Python search data within XML elements

Question

I thought this would work for searching for tag values of "error"

import xml.etree.cElementTree as ET

xml = """
  <tag1>
    <tag2>
      error
    </tag2>
    <tag3>
      working
    </tag3>
    <tag4>
      <tag5>
        error
      </tag5>
    </tag4>
  </tag1>
"""

for event, element in ET.fromstring(xml):
  if element.text.strip() == "error":
    print element.tag

I run in to the following error:

Traceback (most recent call last):
  File "test.py", line 19, in <module>
    for event, element in ET.fromstring(xml):
ValueError: need more than 0 values to unpack

What does "need more than 0 values to unpack" mean?

Answer 1

Iterating over a Element object yields just one element at a time, but your loop is expecting two values. You are confusing .fromstring() with .iterparse() here.

You really just need .findall():

tree = ET.fromstring(xml)
for elem in tree.findall('.//*'):
    if elem.text and elem.text.strip() == 'error':
        print elem.tag

or .iter(), which does the same (loop over all elements in the tree):

tree = ET.fromstring(xml)
for elem in tree.iter():
    if elem.text and elem.text.strip() == 'error':
        print elem.tag

If you really wanted to use the event-driver iterparse you'd need to provide a file object:

from cStringIO import StringIO
for event, element in ET.iterparse(StringIO(xml)):
    if element.text.strip() == "error":
        print element.tag

All snippets print:

tag2
tag5