Install pyenv with Homebrew.
brew install pyenv
Get Zsh and Fish configurations for pyenv from Dotfiles with wget.
wget -P ~/.config/zsh/zshenv https://raw.githubusercontent.com/lukejanicke/dotfiles/master/.config/zsh/zshenv/pyenv.zsh
wget -P ~/.config/fish/conf.d https://raw.githubusercontent.com/lukejanicke/dotfiles/master/.config/fish/conf.d/pyenv.fish
For Fish, contrary to the installation instructions, you do not need to run set -Ux PYENV_ROOT $HOME/.pyenv
and fish_add_path $PYENV_ROOT/bin
at the command line if pyenv was installed via Homebrew. That step is for a Git installation only.