What the code you posted is doing is combining all the elements regardless of whether or not an element with the same tag already exists. So you need to iterate over the elements and manually check and combine them the way you see fit, because it is not a standard way of handling XML files. I can’t explain it better than code, so here it is, more or less commented:
from xml.etree import ElementTree as et
class XMLCombiner(object):
def __init__(self, filenames):
assert len(filenames) > 0, 'No filenames!'
# save all the roots, in order, to be processed later
self.roots = [et.parse(f).getroot() for f in filenames]
def combine(self):
for r in self.roots[1:]:
# combine each element with the first one, and update that
self.combine_element(self.roots[0], r)
# return the string representation
return et.tostring(self.roots[0])
def combine_element(self, one, other):
"""
This function recursively updates either the text or the children
of an element if another element is found in `one`, or adds it
from `other` if not found.
"""
# Create a mapping from tag name to element, as that's what we are fltering with
mapping = {el.tag: el for el in one}
for el in other:
if len(el) == 0:
# Not nested
try:
# Update the text
mapping[el.tag].text = el.text
except KeyError:
# An element with this name is not in the mapping
mapping[el.tag] = el
# Add it
one.append(el)
else:
try:
# Recursively process the element, and update it in the same way
self.combine_element(mapping[el.tag], el)
except KeyError:
# Not in the mapping
mapping[el.tag] = el
# Just add it
one.append(el)
if __name__ == '__main__':
r = XMLCombiner(('sample1.xml', 'sample2.xml')).combine()
print '-'*20
print r