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.