You are probably looking for something like lxml.

Please have a look at the lxml webpage

You can install it in ubuntu with

sudo apt-get install python-lxml

It's in the stdlib: http://docs.python.org/2/library/xml.etree.elementtree.html. No need to install it with pip.

There is no python-xml package in the repository. What made you decide you need a package with that specific name? Are you looking for python-lxml instead? This is the common Python XML library that I believe most people use.

Since you're on Ubuntu, don't bother with those source packages. Just install those development packages using apt-get.

apt-get install libxml2-dev libxslt1-dev python-dev

If you're happy with a possibly older version of lxml altogether though, you could try

apt-get install python-lxml

and be done with it. :)

I had a similar problem, and I fixed it this way on Ubuntu 20.04 with Python 3.1.8.

Go to the terminal and type these commands:

1. cd /home/user/.local/lib/python3.8/site-packages/lxml (Change the "user" keyword according to your system.)
2. mv etree.pyx etree.py  

You can do it manually by going to: 

/home/user/.local/lib/python3.8/site-packages/lxml 

and rename etree.pyx to etree.py.
Then try to import lxml.etree, and hopefully it will work for you.

Just do:

sudo apt-get install python-lxml

For Python 2 (e.g., required by Inkscape):

sudo apt-get install python2-lxml

If you are planning to install from source, then albertov's answer will help. But unless there is a reason, don't, just install it from the repository.