Lazy loading virtualenv in zsh

.zshrc

# virtualenvwrapper
# lazy loading saves on shell startup time
workon() {
  [ -z "$PROJECT_HOME" ] && {
    unset -f workon;
    export WORKON_HOME=$HOME/.virtualenvs;
    export PROJECT_HOME=$HOME/Documents/Python;
    source /usr/local/bin/virtualenvwrapper.sh
    }
  workon "$@"
}
# I have shaved c.a. 0.6-0.7 sec on terminal/zsh/oh-my-zsh startup
# 0.4sec through some cleanup in .zshrc - fpath, getting rid of compinit
# Another 0.3sec through this code which lazy loads virtualenv wrapper