Using pyenv

pyenv.sh

# INSTALLATION

# Step 1: Install pyenv
curl -L https://raw.githubusercontent.com/pyenv/pyenv-installer/master/bin/pyenv-installer | bash
# This will output some instructions to add a few lines to
# your ~/.bash_profile file. Once you've done that 
# then open a new terminal window to continue.

# Step 2: Install some versions of Python
# This will take a few minutes
pyenv install 3.6.3
pyenv install 2.7.14
pyenv rehash # or open a new terminal window again

# Step 3: Set your global default version of Python
# This will make "python" and "python3" run Python 3.6.3
# "python2" can be used to run Python 2.7.14
pyenv global 3.6.3 2.7.14

# WITHIN A PROJECT

# Step 1: Create a virtualenv with your project name
pyenv virtualenv pyquil

# Step 2: Set this virtualenv to be the default for the project
pyenv local pyquil

# Done! This creates a ".python-version" file in your project
# Now, whenever you cd into the directoy, pyenv will automagically
# switch to that environment