python: Change version

Sometimes it can be helpful to switch between python versions 2<->3. Follow these points to switch between them.

Combined

1. Install and create a new environment directly: conda create --name <name> python=x.x
conda create --name py36 python=3.6

Make sure IPython calls the right python version

If not follow these steps, and go to your environment:

1. cd $HOME/anaconda/envs/<name>/bin
   
2. vi ipython
3. change the version of python to use in the first line (#!<pwd>/python -> #!<pwd>/pythonx.x)

Step by step

1. Install an alternative python environment
   conda install python=2.7.8
   or
   conda install python=3.6.1
   

2. Create an environment for the old and the new python environment
   conda create -n py36 python=3.6.1 anaconda
conda create -n py27 python=2.7.8 anaconda

3. Change to the new environment
   source activate py36