Attribute is not added to xml document with lxml python

Question

This is my XML document, I am trying to add an attribute to item element, in the PyDev debugger in eclipse I see the attribute is added, but once I check the new tree the attribute is not added.

Here is the XML:

<root>
    <login branch="99">
        <command action="create">
            <goods_transfer type="9" book="true" nummer="692" branch_from="99" branch_to="90" CheckQty="0">
                <item article="100500213" main_price="49.950" EAN="5018746059881" amount="1.000" DateTime="20161202112913">
                    <size amount="1.000" index="59" EAN="5018746059881" Name="S 37/38" DateTime="20161202112913">
                    </size>
                </item>
                <item article="100500213" main_price="49.950" EAN="5018746059898" amount="2.000" DateTime="20161202112914">
                    <size amount="2.000" index="60" EAN="5018746059898" Name="M 39/40" DateTime="20161202112914">
                    </size>
                </item>
            </goods_transfer>
        </command>
    </login>
</root>

Here is my code using Python 3.4 from Anaconda:

with open(fileName, 'r+b') as f:
    tree = etree.parse(f)
    for _,element in etree.iterparse(f, tag='item'):
#After this line is executed I see the attribute is added
        element.attrib['DocumentCode'] = 'the value of the attr'
        element.clear()
#When I check the new file the attribute is not added
    tree.write(fileName)

What I aim for is this:

                <item article="100500213" main_price="49.950" EAN="5018746059881" amount="1.000" DateTime="20161202112913" DocumentCode='the value of the attr'>
                    <size amount="1.000" index="59" EAN="5018746059881" Name="S 37/38" DateTime="20161202112913">
                    </size>
                </item>

I edited the answer, added the example output I am looking for, please check the item element, the new attribute is the last one I am trying to add. — techhighlands
– techhighlands, Commented Dec 3, 2016 at 13:37
Remove the line : element.clear(). "Resets an element. This function removes all subelements, clears all attributes and sets the text and tail properties to None." [documentation] — har07
– har07, Commented Dec 3, 2016 at 14:04

Tiger-222 · Accepted Answer · 2016-12-03 14:13:57Z

1

This code should work as you want:

from io import StringIO
from lxml import etree


fileName = '...'
context = etree.iterparse(fileName, tag='item')

for _, element in context:
    element.attrib['DocumentCode'] = 'the value of the attr'

with open(fileName, 'wb') as f:
    f.write(etree.tostring(context.root, pretty_print=True))

answered Dec 3, 2016 at 14:13

Tiger-222

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Tiger-222 Over a year ago

Little reminder: stackoverflow.com/help/someone-answers, if the answer is good for you :)

nick_gabpe · Accepted Answer · 2016-12-03 14:26:01Z

0

import xml.etree.ElementTree as et
with open(filename, 'r+b') as f:
    tree = et.parse(f):
    [tr.attrib.update({"aaaa":"bbbb"}) for tr in tree.iter() if tr.tag== "item"]
    tr.write(output)

Here is possibility to do it with standart lib.

answered Dec 3, 2016 at 14:26

nick_gabpe

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