pyenv/libexec/pyenv-prefix

#!/usr/bin/env bash
set -e
[ -n "$PYENV_DEBUG" ] && set -x

# Provide pyenv completions
if [ "$1" = "--complete" ]; then
  echo system
  exec pyenv-versions --bare
fi

if [ -n "$1" ]; then
  export PYENV_VERSIONS=($@)
else
  IFS=: PYENV_VERSIONS=($(pyenv-version-name))
fi

if [ "$PYENV_VERSIONS" = "system" ]; then
  PYTHON_PATH="$(pyenv-which python)"
  echo "${PYTHON_PATH%/*}"
  exit
fi

PYENV_PREFIX_PATHS=()
for PYENV_VERSION in "${PYENV_VERSIONS[@]}"; do
  PYENV_PREFIX_PATH="${PYENV_ROOT}/versions/${PYENV_VERSION}"
  if [ -d "$PYENV_PREFIX_PATH" ]; then
    PYENV_PREFIX_PATHS=("${PYENV_PREFIX_PATHS[@]}" "$PYENV_PREFIX_PATH")
  else
    echo "pyenv: version \`${PYENV_VERSION}' not installed" >&2
    exit 1
  fi
done

IFS=: echo "${PYENV_PREFIX_PATHS[*]}"