zsh autocompletion for activating python virtualenvs

.zshrc

# zsh example for python virtualenv activation shortcuts with autocomplete
#
# - Assumes your virtualenvs are stored in the directory ~/virtualenvs
#
# To use, type activate, then press tab to get a list of available virtualenvs
# Example: act<tab> ans<tab> to do "activate ~/virtualenvs/ansible"

# 1. Activate enhanced completion in zsh
autoload -Uz compinit && compinit

# 2. Create alias shortcut to activate a python virtualenv
activate() { source ~/virtualenvs/$1/bin/activate }

# 3. Define autocomplete for available virtualenvs
compdef '_files -W $HOME/virtualenvs -/ -S "" -F "*/*"' activate