I've installed Anaconda and created two extra environments: py3k (which holds Python 3.3) and py34 (which holds Python 3.4). Besides those, I have a default environment named 'root' which the Anaconda installer created by default and which holds Python 2.7. This last one is the default, whenever I launch 'ipython' from the terminal it gives me version 2.7. In order to work with Python 3.4, I need to issue the commands (in the shell)
source activate py34
First, make sure you have the latest version of conda by running
conda update conda
conda update --all python=3.5
This will attempt to update all your packages in your root environment to Python 3 versions. If it is not possible (e.g., because some package is not built for Python 3), it will give you an error message indicating which package(s) caused the issue.
If you installed packages with pip, you'll have to reinstall them.