I have both python2.7 and python3.2 installed in Ubuntu 12.04.
The symbolic link python links to python2.7
I had the same problem while trying to install pylab, and I have found this link
So what I have done to install pylab within Python 3 is:
python3 -m pip install SomePackage
It has worked properly, and as you can see in the link you can do this for every Python version you have, so I guess this solves your problem.