You need correct xml for parser correct. For reference using Xml.etree Python.
See example:
>>> import xml.etree.ElementTree as ET
>>> tree = ET.fromstring('<part> <part_id>151</part_id> <part_name>BBa_B0034</part_name> <part_short_name>B0034</part_short_name> <part_short_desc>RBS (Elowitz 1999) -- defines RBSefficiency</part_short_desc> <part_type>RBS</part_type> <release_status>Released HQ 2013</release_status> <sample_status>In stock</sample_status> <part_results>Works</part_results> <part_nickname/> <part_rating>1</part_rating> <part_url>http://parts.igem.org/Part:BBa_B0034</part_url> <part_entered>2003-01-31</part_entered></part>')
>>> tree.findall('./part_name')[0].text
'BBa_B0034'