Multiple python installations - setting path variable

How do I tell python to load the 3.2 version of scipy and not the 2.7

Every python version manages its own set of installed modules. The idea is to invoke the pip executable that belongs to the right python version.

From what you described it seems that you have installed the ipython module in your python2.7 interpreter, but your pip executable belongs to the python3.2 interpreter.

The easiest way to execute python2.7's pip is:

sudo ipython -m pip install --upgrade scipy

However this installs scipy as root into your system files and thus usually interferes with versions installed by package managers.

An arguably better way is to install packages in your user's home directory.

ipython -m pip install --upgrade scipy --user

As pointed out in the comments, probably the best way is to get familiar with virtualenv.

I myself find anaconda particularly appealing, since it comes with a clean way of installing and managing multiple python interpreters with a focus on scientific packages across many platforms.