Import ElementTree with preference to faster libraries

etree_import.py

def etree(packages=('lxml.etree', 'xml.etree.cElementTree',
                    'cElementTree', 'elementtree.ElementTree')):
    for pkg_name in packages:
        try:
            pkg = __import__(pkg_name)
        except ImportError:
            continue
        else:
            for subpkg_name in pkg_name.split('.')[1:]:  # skip the base package
                pkg = getattr(pkg, subpkg_name)
            return pkg
    raise ImportError('ElementTree library could not be found')

# If this makes you queasy, rename the function above to _import_etree
etree = etree()