Using SimpleXMLTreeBuilder in elementtree

Question

I have been developing an application with django and elementtree and while deploying it to the production server i have found out it is running python 2.4. I have been able to bundle elementtree but now i am getting the error:

"No module named expat; use SimpleXMLTreeBuilder instead"

Unfortunately i cannot upgrade python so im stuck with what i got. How do i use SimpleXMLTreeBuilder as the parser and/or will i need to rewrite code?

Seminar

Answer 1

If you have third party module that wants to use ElementTree (and XMLTreeBuilder by dependency) you can change ElementTree's XMLTreeBuilder definition to the one provided by SimpleXMLTreeBuilder like so:

from xml.etree import ElementTree # part of python distribution
from elementtree import SimpleXMLTreeBuilder # part of your codebase
ElementTree.XMLTreeBuilder = SimpleXMLTreeBuilder.TreeBuilder

Now ElementTree will always use the SimpleXMLTreeBuilder whenever it's called.

See also: http://groups.google.com/group/google-appengine/browse_thread/thread/b7399a91c9525c97

Grotesque

I've got the following warning using your solution: DeprecationWarning: The xmllib module is obsolete. Use xml.sax instead. Any thoughts how to fix it? – Sapota

Answer 2

We ran into this same problem using python version 2.6.4 on CentOS 5.5.

The issue happens when the expat class attempts to load the pyexpat modules, see /usr/lib64/python2.6/xml/parsers/expat.py

Looking inside of /usr/lib64/python2.6/lib-dynload/, I didn't see the "pyexpat.so" shared object. However, I did see it on another machine, which wasn't having the problem.

I compared the python versions (yum list 'python*') and identified that the properly functioning machine had python 2.6.5. Running 'yum update python26' fixed the issue for me.

If that doesn't work for you and you want a slapstick solution, you can copy the SO file into your dynamic load path.

Whomsoever

Answer 3

Assuming you're now using elementtree.XMLTreeBuilder, just try this instead:

from elementtree import SimpleXMLTreeBuilder as XMLTreeBuilder

It tries to provide exactly the same functionality but using xmllib instead of expat. If that also fails, BTW, try:

from elementtree import SgmlopXMLTreeBuilder as XMLTreeBuilder

to attempt to use yet another implementation, this one based on sgmlop instead.

Virgievirgil

Answer 4

from elementtree import SimpleXMLTreeBuilder as XMLTreeBuilder

Ok, it has slightly changed now:

Traceback (most recent call last):
  File "C:\Python26\tests\xml.py", line 12, in <module>
    doc = elementtree.ElementTree.parse("foo.xml")
  File "C:\Python26\lib\site-packages\elementtree\ElementTree.py", line 908, in parse
    tree = parser_api.parse(source)
  File "C:\Python26\lib\site-packages\elementtree\ElementTree.py", line 169, in parse
    parser = XMLTreeBuilder()
  File "C:\Python26\lib\site-packages\elementtree\ElementTree.py", line 1165, in __init__
    "No module named expat; use SimpleXMLTreeBuilder instead"
ImportError: No module named expat; use SimpleXMLTreeBuilder instead

I think it was statically linked with older version of Python or something. Is there an easy way to attach XML parser to Python 2.6? Some libraries seem to only work with older versions 8(

Dovap

Answer 5

I have same error as you when I developed on Solaris & python 2.7.2. I fixed this issue after I installed the python expat package by using pkgin. See if the solution above can give you any idea.

Seiter