Interactive ZSH wrapper/alias for versioned Python commands to select version when no version provided (e.g. ipython -> ipython2 or ipython3)

py_aliases.zsh

_py_version() {
  PY_VERSIONS=(2 3)

  LINE=(${(s: :)history[$HISTCMD]})
  COMMAND=${LINE[1]}
  ARGS=${(j: :)LINE[2,-1]}

  while (( 1 )) {
    read -s -k1 VERSION"?$COMMAND [${PY_VERSIONS[1]}]: "
    if [[ $VERSION == $'\n' ]]; then
      VERSION=${PY_VERSIONS[1]}
      break
    elif (( ${PY_VERSIONS[(I)$VERSION]} )); then
      echo $VERSION
      break
    fi
    echo "$VERSION is not supported (${(j:, :)PY_VERSIONS})"
  }

  if [[ -x $(which $COMMAND$VERSION) ]]; then
    COMMAND=$COMMAND$VERSION
  else
    COMMAND="python$VERSION $(which -a $COMMAND | grep -v aliased | head -n 1)"
  fi
  eval $COMMAND $ARGS
}

# versioned python commands
alias python="_py_version"
alias pip="_py_version"
alias pydoc="_py_version"
alias idle="_py_version"
alias ipython="_py_version"
alias jupyter="_py_version"