This article proposes a proven standard which enables automatic virtualenv activation.

Demonstration

Before, I had to do something like:

cd myproject
source ../env/bin/activate

Now I just do:

cd myproject

Virtualenv standard

Say I have a project called projectX, you could expect to find it as such on my servers:

/srv
    /projectX_prod
    /projectX_test
    /projectX_dev
        /projectX_dev_env -> the virtualenv
        /env -> symlink to projectX_dev_env
        /main -> the checkout of the python project

As you can see, it is easy and consistent. For the record, this is the command I use to create the symlink:

cd /srv/projectX_prod
ln -sfn projectX_dev_env env

Shell hack

Usually, when I want to hack a project, it starts with:

cd /srv/projectX_dev

Or even:

cd /srv/projectX_dev/main

I know that this is always how it will start. So I added a hack in my shell init script to enable the corresponding virtualenv automatically. It is pretty self explanatory, so you should be able to hack it easily:

function cd() {
    builtin cd $@;
    if [ -f env/bin/activate ]
    then
        source env/bin/activate
    elif [ -f bin/activate ]
    then
        source bin/activate
    elif [ -f ../env/bin/activate ]
    then
        source ../env/bin/activate
    fi 
}