XML Stack Overflow

I can't seem to figure out how to get cElementTree to recurse into xml import elements. I presume I'm missing something simple here.

<import file="xmlfile_imported.xml"/>

code I'm using

try:
    import cElementTree as ET
except ImportError:
  try:
    # Python 2.5 need to import a different module
    import xml.etree.cElementTree as ET
  except ImportError:
    exit_err("Failed to import cElementTree from any known place")
def_file="xmlfile.xml"
try:
    tree = ET.parse(open(def_file, "r"))
    root = tree.getroot()
except:
    exit_err("Unable to open and parse input definition file: " + def_file)

for child in root:
    print(child.tag, child.attrib);

Using this code I will only see the content of the xmlfile.xml but not the content of xmlfile_imported.xml.

what am I doing wrong here?