virtualenvwrapper and Python 3

Question

If you already have python3 installed as well virtualenvwrapper the only thing you would need to do to use python3 with the virtual environment is creating an environment using:

which python3 #Output: /usr/bin/python3
mkvirtualenv --python=/usr/bin/python3 nameOfEnvironment

Or, (at least on OSX using brew):

mkvirtualenv --python=`which python3` nameOfEnvironment

Start using the environment and you'll see that as soon as you type python you'll start using python3

You can make virtualenvwrapper use a custom Python binary instead of the one virtualenvwrapper is run with. To do that you need to use VIRTUALENV_PYTHON variable which is utilized by virtualenv:

$ export VIRTUALENV_PYTHON=/usr/bin/python3
$ mkvirtualenv -a myproject myenv
Running virtualenv with interpreter /usr/bin/python3
New python executable in myenv/bin/python3
Also creating executable in myenv/bin/python
(myenv)$ python
Python 3.2.3 (default, Oct 19 2012, 19:53:16) 
[GCC 4.7.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.

The latest version of virtualenvwrapper is tested under Python3.2. Chances are good it will work with Python3.3 too.

virtualenvwrapper now lets you specify the python executable without the path.

So (on OSX at least)mkvirtualenv --python=python3 nameOfEnvironment will suffice.

On Ubuntu; using mkvirtualenv -p python3 env_name loads the virtualenv with python3.

Inside the env, use python --version to verify.

You can add this to your .bash_profile or similar:

alias mkvirtualenv3='mkvirtualenv --python=`which python3`'

Then use mkvirtualenv3 instead of mkvirtualenv when you want to create a python 3 environment.

I find that running

export VIRTUALENVWRAPPER_PYTHON=/usr/bin/python3

and

export VIRTUALENVWRAPPER_VIRTUALENV=/usr/bin/virtualenv-3.4

in the command line on Ubuntu forces mkvirtualenv to use python3 and virtualenv-3.4. One still has to do

mkvirtualenv --python=/usr/bin/python3 nameOfEnvironment

to create the environment. This is assuming that you have python3 in /usr/bin/python3 and virtualenv-3.4 in /usr/local/bin/virtualenv-3.4.