Cheap hack to emulate virtualenvwrapper's workon script

workon.sh

function workon () {
    # Find the configured virtualenvwrapper home, or use Kirk's
    # clearly excellent choice.
    if [[ -z $PROJECT_HOME ]]; then
        envs=$PROJECT_HOME
    else
        envs=~/Envs
    fi

    # Override the paths for specific environments
    case $1 in
        data_builders)
            cd ~/Envs/data-pipelines/data_builders
            ;;
        *)
            cd ~/Envs/$1
            ;;
    esac

    # Open a pipenv shell if possible
    if [[ -e Pipfile ]]; then
        pipenv shell
    fi
}

I've switched from using virtualenvwrapper to pipenv as it better fits my workflow. I really missed that lovely workon command, though. This is my attempt at more or less emulating its behavior:

$ which python
/usr/local/bin/python

$ python --version
Python 2.7.14

$ workon data_builders
Spawning environment shell (/usr/local/bin/zsh). Use 'exit' to leave.
source /Users/kirk/.local/share/virtualenvs/data_builders-ulboz1a4/bin/activate

$ source /Users/kirk/.local/share/virtualenvs/data_builders-ulboz1a4/bin/activate

$ which python
/Users/kirk/.local/share/virtualenvs/data_builders-ulboz1a4/bin/python

$ python --version
Python 3.6.3

Notes

I use Zsh, but this also works in Bash.

I create all my virtualenvs in ~/Envs. Set $PROJECT_HOME to your own preferred path (which you've probably already done if you'd previously used virtualenvwrapper).