pyenv for multiple Python installations on OS X.

$ brew update
$ brew install pyenv
$ pyenv install 3.5.0
$ pyenv install 3.4.3
$ pyenv install 3.3.6
$ pyenv install 3.2.6
$ pyenv install 2.7.10
$ pyenv install 2.6.9
$ pyenv versions
* system (set by /Users/bouke/.pyenv/version)
  2.6.9
  2.7.10
  3.2.6
  3.3.6
  3.4.3
  3.5.0

Then, when you need a certain version:

pyenv local 3.5.0

This will create a file .python-version, so pyenv will remember the Python version for this directory.