Interesting lxml Gotcha

I have been using lxml to generate XML to interface with Authorize.net's CIM API and I noticed something. Element does not behave as expected, which is supposed to be as a list. The key difference is with references to the same Element. 

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#!/usr/bin/env python
from lxml import etree

root = etree.Element('root')
child = etree.Element('child')
root.append(child)
root.append(child)
print etree.tostring(root, pretty_print=True)

If you run this, you will get the following output: 

<root>
  <child/>
</root>

One child when we are expecting two. This is a bug. The workaround is to use deepcopy. 

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#!/usr/bin/env python
from copy import deepcopy
from lxml import etree

root = etree.Element('root')
child = etree.Element('child')
root.append(child)
root.append(deepcopy(child))
print etree.tostring(root, pretty_print=True)

This results with the expected output: 

<root>
  <child/>
  <child/>
</root>
Posted by Tyler Lesmann on February 10, 2009 at 12:55
Tagged as: gotcha lxml python
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#1 jesse Dziedzic wrote this 3 months, 2 weeks ago

At least some bloggers can write. My thanks for this piece..

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