Install the Latest Python Versions on Mac OSX¶

2017-10-12 Discuss

Once you have decided that Python is an awesome language to learn and you have heard all about the the cool features awaiting you, you are determined to install the latest versions on your laptop so that you can start developing.

What’s New In Python 3.6 - December 23, 2016
What’s New In Python 3.5 - September 13, 2015
What’s New In Python 3.4 - March 16, 2014
What’s New In Python 3.3 - September 29, 2012
What’s New In Python 3.2 - February 20, 2011
What’s New In Python 3.1 - June 27, 2009
What’s New In Python 3.0 - December 3, 2008
What’s New In Python 2.7 - July 3, 2010
What’s New In Python 2.6 - October 1, 2008

You may be a little concerned about the differences between Python 2 and Python 3, so you want to make sure that you have the latest versions of each available. This will enable you to switch between them easily and work on porting Python 2 programs to Python 3.

OS vendor Python versions lag behind the latest available and can only be updated by installing a major patch or bolting-on an additional Python installation:

OS Version	System Python Version
OSX 10.13	2.7.10
OSX 10.12	2.7.10
OSX 10.11	2.7.10
Ubuntu 16.04 LTS Xenial Xerus	2.7.11
Ubuntu 14.04 LTS Trusty Tahr	2.7.5
Ubuntu 12.04 LTS Precise Pangolin	2.7.3

One way to work around this issue is to use pyenv to install the versions of Python you want to use. This tool provides a simplified build environment for installing the Pythons you want, while providing a set of shell script shims that makes it easy to switch between them. This tool was inspired by and forked from rbenv and ruby-build.

Install Python with pyenv¶

Start a Terminal session.

Install Homebrew and Xcode Command Line Tools.

xcode-select --install

/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

Install pyenv.
```
brew install pyenv
```
If you already have pyenv installed, you can upgrade it to gain access to the latest Python versions. The pyenv tool is updated periodically with new formulas for the latest releases.
```
brew upgrade pyenv
```
Add configuration to your .bash_profile to initialize pyenv every time you start a new Terminal. The PYENV_ROOT, which is where Python versions and packages will be installed, defaults to $HOME/.pyenv.
```
cat >>$HOME/.bash_profile <<"EOF"
if which pyenv > /dev/null 2&>1; then eval "$(pyenv init -)"; fi
EOF
```
Load your .bash_profile configuration changes.
```
source $HOME/.bash_profile
```
List the available Python versions. Notice that you have access to several different distributions: python.org (plain version numbers), anaconda, ironpython, jython, miniconda, pypy and stackless. We will install the standard Python versions released by python.org, otherwise known as CPython, because the interpreter is written in C.
```
pyenv install --list
```
If you are running OSX 10.13, you will need to set the following environment variables, when you install new Python versions. See #988 for more details.
```
export CFLAGS="-I$(brew --prefix openssl)/include"
export LDFLAGS="-L$(brew --prefix openssl)/lib"
```

Install Python versions.

pyenv install 2.7.14
pyenv install 3.6.3

List the available Python versions.
```
pyenv versions
```
Activate a Python version and verify that it is available.
```
pyenv global 2.7.14
pyenv versions
python -V
```
Activate another Python version and verify that it is available.
```
pyenv global 3.6.3
pyenv versions
python -V
```
If desired, activate multiple Python versions and verify that they are available. PEP 394 -- The "python" Command on Unix-Like Systems explains conventions for naming python binaries.
```
pyenv global 2.7.14 3.6.3
pyenv versions
python -V
python2 -V
python2.7 -V
python3 -V
python3.6 -V
```

Create new directories for Python projects, add pyenv local version files and verify the Python versions. Your python version will automatically switch when you change into these directories.

mkdir python2-project
cd python2-project
pyenv local 2.7.13
cat .python-version
pyenv local
python -V
cd ..

mkdir python3-project
cd python3-project
pyenv local 3.6.3
cat .python-version
pyenv local
python -V
cd ..

Useful Python Packages¶

This is a small collecton of useful packages that will help get you started doing useful things with Python.

Install flake8, which is a static analyzer that enforces good Python coding style and alerts you to coding mistakes. Now that you have Python installed, you can use the pip command to install any additional modules that you want to use. You will need to install modules separately for each version of Python you are actively using.

pip install flake8

Install advanced Python Read-Eval-Print-Loop (REPL) packages, which will make it easier to explore Python code, because they grant access to tab completion and fancy editing capabilities. The ipython tool is a command line REPL, which can be exited with ctrl-d. Jupyter Notebook is a browser-based REPL that operates on individual cells of code. The IPython Interactive Computing website has more information on these tools.

pip install ipython jupyter
ipython
jupyter notebook

Install Requests: HTTP for Humans, which makes it easy to consume HTTP services. See GitHub's REST API v3 documentation for more details on endpoints that are avaialble.

pip install requests

python
>>> import requests
>>> r = requests.get('https://api.github.com/users/copperlight')
>>> r.ok
True
>>> r.status_code
200
>>> r.headers['content-type']
'application/json; charset=utf8'
>>> r.encoding
'utf-8'
>>> r.text
u'{"login":"copperlight", ...}'
>>> r.json()
{u'public_repos': 27, ...}
>>> r.json()['login']
u'copperlight'

Install Flask: A Python Microframework, which can be used to quickly build small websites that automate everyday tasks.

pip install Flask

from flask import Flask
app = Flask(__name__)

@app.route("/")
def hello():
    return "Hello World!"

FLASK_APP=hello.py flask run
curl http://127.0.0.1:5000

If you need Python package isolation on a per-project basis, because you have conflicting sets of packages specified for different projects, you can use virtualenv to set up separate environments. The virtualenv tool establishes a clean room Python installation, either based upon the current version of Python in use, or a version specified on the command line. If you have multiple Python versions activated in pyenv, you can use virtualenv to switch between them easily.

pip install virtualenv
pip list

mkdir python2-project
cd python2-project
virtualenv -p python2.7 venv
source venv/bin/activate
python -V
which python
pip list
which pip
deactivate
cd ..

mkdir python3-project
cd python3-project
virtualenv -p python3.6 venv
source venv/bin/activate
python -V
which python
pip list
which pip
deactivate
cd ..

Automated Testing with Python¶

While working on Python programs, you may be interested in automating testing. The most common choice for implementing this is tox, which will allow you to run tests with multiple different versions of Python, if needed.

Python Packaging¶

After completing a Python program or two, you will be interested in learning how to distribute them effectively. The Python Packaging User Guide has some good advice on this topic.

Quickstart Commands¶

# if you need homebrew
xcode-select --install
/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

# install pyenv and latest major python versions
brew install pyenv

cat >>$HOME/.bash_profile <<"EOF"
if which pyenv > /dev/null; then eval "$(pyenv init -)"; fi
EOF

source $HOME/.bash_profile

pyenv install 2.7.14
pyenv install 3.6.3
pyenv versions