Table of Contents

• HomeBrew
• pyenv
  • Install
  • Setup Environment
  • Examine Installation
  • Useful Commands
• Python
  • Install
  • Use Multiple versions
• pyenv-virtualenv
  • Install
  • Setup Environment
  • Set and Activate Environment

Mac already provides python 2.7. However, I needed to use Django with python 3.6 for a demo on my Mac. Thus, I installed pyenv and pyenv-virtualenv for convenience.

Pyenv is light but strong. By pyenv, users can manage multiple versions of python on one system. And its plugin pyenv-virtualenv can create several virtual environment which allows users working independently.

Here is link to the doc for pyenv. As author recommended, I use HomeBrew to install pyenv.

- HomeBrew

• If you are new to HomeBrew, just come here to learn it.
• If you already install it, please update it by brew update in Terminal before installing.

- pyenv

— Install

Open Terminal and type brew install pyenv to install pyenv

— Setup Environment

1. Open Terminal.
2. Go to home folder by typing cd or cd ~ in Terminal.
3. Open .bash_profile (If not existed, just create one) by any editors (nano, vim, etc).
4. Type following code. Then save and exit editor.

   export PYENV_ROOT="$HOME/.pyenv"
   export PATH="$PYENV_ROOT/bin:$PATH"
   eval "$(pyenv init -)"
   

5. Make it effect immediately by typing source .bash_profile in Terminal

— Examine Installation

In Terminal, enter command pyenv. If it shows a guide, you install pyenv successfully.

— Useful Commands

• pyenv install [version]: install python with “version”
• pyenv uninstall [version]: uninstall python with “version”
• pyenv version: display current version of Python
• pyenv versions: display all versions of Python that you already installed

- Python

— Install

As learned from “Useful Commands” for pyenv, now we can use pyenv install to install.

For example, pyenv install 3.6.1 will install Python 3.6.1.

Note that, if you fail to install, there are may two reasons:

• Version is not valid or not existed. Command pyenv install --list will list up available versions.
• Your pyenv is out of update. Update by brew update pyenv before installing.

— Use Multiple versions

1. Go to the folder you are going to work in Terminal.
2. Type command pyenv local [version]. This indicates python [version] will be locally applied in this folder.
3. pyenv version examines whether you setup successfully.

- pyenv-virtualenv

pyenv-virtualenv is not neccessary but improve experience. It activates a virtual environment so that user can work with specific python version anywhere under this environment. Here is the link.

— Install

Type brew install pyenv-virtualenv in Terminal.

— Setup Environment

1. Open Terminal.
2. Go to home folder by typing cd or cd ~ in Terminal.
3. Open .bash_profile (If not existed, just create one) by any editors (nano, vim, etc).
4. Type following code. Then save and exit editor.

   eval "$(pyenv init -)"
   eval "$(pyenv virtualenv-init -)"
   

5. Make it effect immediately by typing source .bash_profile in Terminal

There are other options list in doc. You can check the link and setup by yourself.

— Set and Activate Environment

1. Type command pyenv virtualenv [version] [alias] in Terminal. This will create a environment named “alias” with Python [version].

For example, pyenv virtualenv 3.6.1 py361 will create a environment “py361” with Python 3.6.1.

1. Type command pyenv activate [alias] in Terminal. It actives the environment named “alias”.

For example, pyenv activate py361 will activate the environment named “py361”.

If you forget, check list of created virtual environment by pyenv virtualenvs.

Additionally, pyenv deactivate will leave this virtual environment.

Note that, we only can create virtual environment with installed python version.