ZSH profile function to define a binary in its own pyenv virtualenv and setup if not already

pyenv_venv_command.zsh

# use as follows
# COMMAND=pyenv_venv_command command
# $COMMAND params
function pyenv_venv_command() {

    COMMAND=$1

    if (( ! $+commands[pyenv] )); then
        echo "no pyenv" 1>&2
        which $COMMAND
    fi

    PACKAGE=$1
    VIRTUALENV_NAME=$1
  
    if [[ -v 2 ]]; then
        PACKAGE=$2
    fi


    if [[ -v 3 ]]; then
        VIRTUALENV_NAME=$3
    fi


    if PYENV_VERSION=$VIRTUALENV_NAME pyenv which $COMMAND 2> /dev/null | grep '.pyenv/versions' > /dev/null 2&>1; then
        PYENV_VERSION=$VIRTUALENV_NAME pyenv which $COMMAND
    else
        if [[ -v 4 ]]; then
            PYENV_TARGET_VERSION=$4
            if ! pyenv versions | grep " ${PYENV_TARGET_VERSION} " &> /dev/null; then
                pyenv install $PYENV_TARGET_VERSION
            fi
            PYENV_VERSION=$PYENV_TARGET_VERSION pyenv virtualenv $VIRTUALENV_NAME > /dev/null 2&>1
        else
            pyenv virtualenv $VIRTUALENV_NAME > /dev/null 2&>1
        fi
        PYENV_VERSION=$VIRTUALENV_NAME pyenv exec pip install $PACKAGE 1>&2
        PYENV_VERSION=$VIRTUALENV_NAME pyenv which $COMMAND
    fi
    
}