How to automatically activate virtualenvs when cd'ing into a directory

Question

I have a bunch of projects in my ~/Documents. I work almost exclusively in python, so these are basically all python projects. Each one, e.g. ~/Documents/foo has its own virtualenv, ~/Documents/foo/venv (they're always called venv). Whenever I switch between projects, which is ~10 times a day, I do

deactivate
cd ..
cd foo
source venv/bin/activate

I've reached the point where I'm sick of typing deactivate and source venv/bin/activate. I'm looking for a way to just cd ../foo and have the virtualenv operations handled for me.

• I'm familiar with VirtualEnvWrapper which is a little heavy-handed in my opinion. It seems to move all your virtualenvs somewhere else, and adds a little more complexity than it removes, as far as I can tell. (Dissenting opinions welcome!)

• I am not too familiar with shell scripting. If you can recommend a low-maintenance script to add to my ~/.zshrc that accomplishes this, that would be more than enough, but from some quick googling, I haven't found such a script.

• I'm a zsh/oh-my-zsh user. oh-my-zsh doesn't seem to have a plugin for this. The best answer to this question would be someone contributing an oh-my-zsh plugin which does this. (Which I might do if the answers here are lackluster.

Answer 1

Add following in your .bashrc or .zshrc

function cd() {
  builtin cd "$@"

  if [[ -z "$VIRTUAL_ENV" ]] ; then
    ## If env folder is found then activate the vitualenv
      if [[ -d ./.env ]] ; then
        source ./.env/bin/activate
      fi
  else
    ## check the current folder belong to earlier VIRTUAL_ENV folder
    # if yes then do nothing
    # else deactivate
      parentdir="$(dirname "$VIRTUAL_ENV")"
      if [[ "$PWD"/ != "$parentdir"/* ]] ; then
        deactivate
      fi
  fi
}

This code will not deactivate the virtualenv even if someone goes into subfolder. Inspired by answers of @agnul and @Gilles.

If the virtualenv is made by pipenv, then please consider this wiki page.

Furthermore, for added security please consider direnv.