This script installs `pyenv` to your home directory. (you can set PYENV_ROOT to change the directory, tho.)

pyenv-installer.sh

#!/usr/bin/env bash

if [ ! $(which git) ]; then
  echo "Git is not installed, can't continue."
  exit 1
fi

if [ -z "${PYENV_ROOT}" ]; then
  PYENV_ROOT="$HOME/.pyenv"
fi

# Install pyenv:
if [ ! -d "$PYENV_ROOT" ] ; then
  git clone https://github.com/yyuu/pyenv.git $PYENV_ROOT
else
  cd $PYENV_ROOT
  if [ ! -d '.git' ]; then
    git init
    git remote add origin https://github.com/yyuu/pyenv.git
  fi
  git pull origin master
fi

# Show help if `.pyenv` is not in the path:
if [ ! $(which pyenv) ]; then
  echo "
Seems you still have not added 'pyenv' to the load path:
# ~/.bash_profile:
export PYENV_ROOT=\"\${HOME}/.pyenv\"
if [ -d \"\${PYENV_ROOT}\" ]; then
  export PATH=\"\${PYENV_ROOT}/bin:\${PATH}\"
  eval \"\$(pyenv init -)\"
fi
"
fi