[lxml] Surprising slicing behaviour

26 Aug 2013

      Hi all

I noticed a behaviour in lxml that surprised me, so I thought I would 
mention it.

Versions - python 3.3.2, lxml 3.2.1.

Consider the following - standard python slicing -
...
...
...
a = [1, 2, 3, 4]
b = [5, 6, 7, 8]
a[:0] = b[0:]
a
[5, 6, 7, 8, 1, 2, 3, 4]
b
[5, 6, 7, 8]
This is what I expected.

Then look at this - lxml slicing -
...
...
...
from lxml import etree
a = etree.fromstring('<a1></a1>')
b = etree.fromstring('<b1></b1>')
a[:0] = b[0:]
etree.tostring(a)
b'<a1></a1>'
etree.tostring(b)
b'<b1/>'
The slicing worked, but it removed the contents of b.

Is this intentional?

Frank Millman