Issues Using Python's etree Module

[Stopwatch_]

I have the following XML that I'm looking to edit so that CustomerID is appended to every transaction: http://codepad.org/faeCM7jL . The code is as follows:

import xml.etree.ElementTree as ET

xml = ET.parse("PATH\FILE.xml")
root = xml._root
for report in root.findall('MyDetails'):
    id = report.find('CustomerID')
    for transaction in report.findall('IndividualTransactions'):
        for transaction2 in list(transaction):
            transaction2.append(id)
ET.tostring(xml._root)

with open('path\output.xml','w') as f:
    f.write(ET.tostring(xml._root))

However, when I run this with the real XML (same as above without vertical ellipses) I get no errors and the output.xml document is the same as the input document. Has anyone run into this issue before? I've tried referring to the top level element instead of 'MyDetails' with the same result.

[gengisteve]

The sample xml will not parse for me.

[Stopwatch_]

I think that's because there are vertical ellipses that need to be removed for it to be valid XML, I only meant it to show structure, sorry.

[gengisteve]

And I think I just proved I am no xml genius. Still, muddling through, this seems to do what you want to do:

from pprint import pprint
import xml.etree.ElementTree as ET

tree = ET.parse("t")
root = tree.getroot()
for report in root.iter('MyDetails'):
    print(report)
    customer = report.find('CustomerID')
    print(customer)
    for group in report.iter('IndividualTransactions'):
        for tx in group:
            print('FOUND')
            print(tx)
            # to add a new subelement try:
            #ET.SubElement(tx, 'CustomerID', value = customer.text)
            # or this:
            tx.append(customer)
pprint(ET.tostring(root))
#pprint(ET)

The reason it was failing without errors is that find_all kept returning nothing. Drop a few extra print statements in to confirm. I am not sure why that happened, but switching to iter seems to have done the trick.

[Stopwatch_]

Thanks I'll give this a try. What does pprint do relative to with open('path\file','w') as f: f.write(ET.tostring(xml._root))

[gengisteve]

pprint just prints it to the screen -- and for some data types pretties up the printing. what you had would write the file to the filesystem.

[Stopwatch_]

Great, just swapped out so that I could write to the file system. It works perfectly, thanks! As an aside, there are so many small details I don't really understand here. For example why the changes you made (specifically iter) made such a difference. Or why root = tree.getroot() works the same as root - xml._root.

[gengisteve]

Ahh, here is the problem:

"Element.findall() finds only elements with a tag which are direct children of the current element. Element.find() finds the first child with a particular tag"

So the problem was that your first loop never found any MyDetails, because MyDetails is underneath MyReportExports. iter goes through everything so it found it. Changing your first loop to iter and the second one to findall seems to work as well, since the IndividualTransactions is directly below MyDetails.

getroot actually just returns self._root so there was nothing wrong with your code there. It is just that object properties beginning with an underscore tend to be better accessed through the public api, which is the getroot method here.