Install pyenv and pyenv-virtualenv

pyenv

Install pyenv

brew update
brew install pyenv

Config

# open .bash_profile by vim
vim ~/.bash_profile

press "i" into insert mode, then enter:

export PYENV_ROOT=/usr/local/var/pyenv
if which pyenv > /dev/null;
  then eval "$(pyenv init -)";
fi

press "esc", then press "shift" + ":", enter w(to save)
press "shift" + ":", enter q(to quit vim)

install python into pyenv

# check which version can be installed
pyenv install --list
# install
pyenv install 3.6.2 # or other version number you want
# check the installed versions
pyenv versions
# uninstall a version
pyenv uninstall 3.6.2 # or other version number you want

Use pyenv to activate python

# set interpreter only in current shell
pyenv shell 3.6.2 
pyenv shell --unset

# set default interpreter for this folder
pyenv local 3.6.2
pyenv local --unset

# set default interpreter for this computer
pyenv global 3.6.2
pyenv global --unset

pyenv-virtualenv

Install pyenv-virtualenv

brew update
brew install pyenv-virtualenv

Config

# open .bash_profile by vim
vim ~/.bash_profile

press "i" into insert mode, then enter:

if which pyenv-virtualenv-init > /dev/null;
  then eval "$(pyenv virtualenv-init -)";
fi

press "esc", then press "shift" + ":", enter w(to save)
press "shift" + ":", enter q(to quit vim)

# assume the current version is 3.6.2
pyenv virtualenv venv36

# assume the current version is 3.6.2
pyenv virtualenv 3.7.3 venv37

# activate your virtualenv
pyenv activate venv36
# deactivate
pyenv deactivate