lxml iterparse in python can't handle namespaces

When there is a namespace attached, the tag isn't a, it's {http://some.random.schema}a. Try this (Python 3):

from lxml import etree
from io import BytesIO

xml = '''\
<root xmlns="http://some.random.schema">
  <a>One</a>
  <a>Two</a>
  <a>Three</a>
</root>'''
data = BytesIO(xml.encode())
docs = etree.iterparse(data, tag='{http://some.random.schema}a')
for event, elem in docs:
    print(f'{event}: {elem}')

or, in Python 2:

from lxml import etree
from StringIO import StringIO

xml = '''\
<root xmlns="http://some.random.schema">
  <a>One</a>
  <a>Two</a>
  <a>Three</a>
</root>'''
data = StringIO(xml)
docs = etree.iterparse(data, tag='{http://some.random.schema}a')
for event, elem in docs:
    print event, elem

This prints something like:

end: <Element {http://some.random.schema}a at 0x10941e730>
end: <Element {http://some.random.schema}a at 0x10941e8c0>
end: <Element {http://some.random.schema}a at 0x10941e960>

As @mihail-shcheglov pointed out, a wildcard * can also be used, which works for any or no namespace:

from lxml import etree
from io import BytesIO

xml = '''\
<root xmlns="http://some.random.schema">
  <a>One</a>
  <a>Two</a>
  <a>Three</a>
</root>'''
data = BytesIO(xml.encode())
docs = etree.iterparse(data, tag='{*}a')
for event, elem in docs:
    print(f'{event}: {elem}')

See lxml.etree docs for more.