Auto-activate Python virtualenvwrapper environment if shell is started within a project directory

gistfile1.txt

# ...

# Copyright © 2021 Nils Philippsen <[email protected]>
# Licensed under the MIT license as published by the Open Source Initiative

# Auto-activate Python virtualenvwrapper environment if shell is started within a project directory
_old_nullglob=$(shopt -p nullglob)
shopt -s nullglob
unset _projdirs_venvs
declare -A _projdirs_venvs
for _venvdir in ${WORKON_HOME:-$HOME/.virtualenvs}/*/; do
    _projfile="${_venvdir}/.project"
    if [ ! -f "$_projfile" ]; then
        continue
    fi
    _venvdir="${_venvdir%%/}"
    _projdir="$(tr -d '\0' < "${_venvdir}/.project")"
    if [ -z "$_projdir" ]; then
        continue
    fi  
    _venv="${_venvdir##*/}"
    _projdirs_venvs[$_projdir]="$_venv"
done

unset _projdirs_sorted
declare -a _projdirs_sorted
while read _projdir; do
    _projdirs_sorted+=("$_projdir")
done < <(for _projdir in "${!_projdirs_venvs[@]}"; do
    echo "$_projdir"
done | sort -r) 
for _projdir in "${_projdirs_sorted[@]}"; do
    if [ "$PWD" = "$_projdir" -o "${PWD#${_projdir}/}" != "$PWD" ]; then
        _venv="${_projdirs_venvs[${_projdir}]}"
        workon -n "$_venv"
        break
    fi 
done
eval $_old_nullglob
unset _old_nullglob _projdirs_venvs _venvdir _projfile _projdir _venv

I often activate a virtual environment (and usually change into its project directory) using workon <envname> (of virtualenvwrapper), then open a new terminal tab or window which – with e.g. gnome-terminal – starts in the same directory. I usually attempt to run something related to the project there right away – which fails, sometimes more, sometimes less obviously, because the virtual environment isn't active.

The snippet above, if put into ~/.bash_profile for login shells, searches for a virtual environment whose project directory is $PWD or a parent, and activates it. If no virtual environment matches, nothing is done.