XML parsing with lxml and Python

Question

Please help me to resolve my problem with lxml
(I'm a newbie to lxml).
How can I get "Comment 1" from the next file:

<?xml version="1.0" encoding="windows-1251" standalone="yes" ?>
<!--Comment 1-->
<a>
   <!--Comment 2-->
</a>

Answer 1

>>> from lxml import etree
>>> tree = etree.parse('filename.xml')
>>> root = tree.getroot()
>>> print root.getprevious()
<!--Comment 1-->

Or to be sure (there might be more than one):

>>> for i in root.itersiblings(tag=etree.Comment, preceding=True):
...     print i
...
<!--Comment 1-->

Use the .text attribute if you want to extract the text of the comment.

Answer 2

Docs: the lxml tutorial, and search for "Comments"

Code:

import lxml.etree as et

text = """\
<?xml version="1.0" encoding="windows-1251" standalone="yes" ?>
<!--Comment 1a-->
<!--Comment 1b-->
<a> waffle
   <!--Comment 2-->
   blah blah
</a>
<!--Comment 3a-->
<!--Comment 3b-->
"""
print "\n=== %s ===" % et.__name__
root = et.fromstring(text)

for pre in (True, False):
    for comment in root.itersiblings(tag=et.Comment, preceding=pre):
        print pre, comment

for elem in root.iter():
    print
    print isinstance(elem.tag, basestring), elem.__class__.__name__, repr(elem.tag), repr(elem.text), repr(elem.tail)

Output:

=== lxml.etree ===
True <!--Comment 1b-->
True <!--Comment 1a-->
False <!--Comment 3a-->
False <!--Comment 3b-->

True _Element 'a' ' waffle\n   ' None

False _Comment <built-in function Comment> 'Comment 2' '\n   blah blah\n'

Comments: doesn't work with xml.etree.cElementTree