Sample METS update script using eulxml.

eulxml_updater_demo.py

from eulxml import xmlmap
from eulxml.xmlmap import load_xmlobject_from_file

MODS_NAMESPACE = 'http://www.loc.gov/mods/v3'
METS_NAMESPACE = 'http://www.loc.gov/METS/'

SF = xmlmap.StringField

class Common(xmlmap.XmlObject):
    "MODS class with namespace declaration common to all MODS XmlObjects."
    ROOT_NS = METS_NAMESPACE
    ROOT_NAME = 'METS'
    ROOT_NAMESPACES = {'mods': MODS_NAMESPACE,
                       'METS': METS_NAMESPACE}

class Public(Common):
    ROOT_NAME = 'rights:Context'
    discover = SF('rights:Permissions/@DISCOVER')
    display = SF('rights:Permissions/@DISPLAY')
    modify = SF('rights:Permissions/@MODIFY')

class Rights(Common):
    ROOT_NAME = 'RightsDeclarationMD'
    public = xmlmap.NodeField('rights:Context[@CONTEXTCLASS="GENERAL PUBLIC"]', Public)

class Mods(Common):
    """Map mods fields."""
    ROOT_NAME = 'mods'
    language_code = xmlmap.StringField('mods:language/mods:languageTerm[@type="code"]')

class BDRMets(Common):
    """BDRMets class."""
    pid = xmlmap.StringField('@OBJID')
    mods = xmlmap.NodeField('//mods:mods', Mods)

#Get the METS as a file or string object.  
handle = open('bdr7275.xml')

#Bind it to the classes.  
mets = load_xmlobject_from_file(handle, BDRMets)

language_code = mets.mods.language_code
#Set code to english if it's italian.  
if language_code == 'ita':
    mets.mods.language_code = 'eng'

#METS now contains updated mods.  
print mets.serialize(pretty=True)

#Update METS datastream with fcrepo.