Setting up OS-X for Python¶

Getting The Tools¶

OS-X comes with Python out of the box, but not the full setup you’ll need for development or this class. It also doesn’t have the latest version(s), and no version of Python 3.

So we recommend installing a new version.

Note:

If you use macports or homebrew to manage *nix software on your machine, feel free to use those for python, git, etc, as well. If not, then read on.

Python¶

While OS-X does provide python out of the box – it tends not to have the latest version, and you really don’t want to mess with the system installation. So I recommend installing an independent installation from python.org:

Download the Python 3.5.2 installer from Python.org:

https://www.python.org/downloads/

Double click the installer and follow the prompts – the defaults are your best bet. Simple as that.

Oddly, this does NOT install a python command, but rather a python3 command. If you want to be able to simply type python and get python3, then you can add a symlink to the install:

$ cd /Library/Frameworks/Python.framework/Versions/3.5/bin
$ ln -s python3.5 python

(or an alias in your shell – an Unix geeks here?)

Once you have done that, you should be able to type python at the command prompt, and get:

$ python
Python 3.5.2 (v3.5.2:4def2a2901a5, Jun 26 2016, 10:47:25)
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>>

Terminal¶

The built-in “terminal” application works fine. Find it in:

/Applications/Utilities/Terminal

Drag it to the dock to easy access.

pip¶

pip is the Python package installer. It is updated faster than python itself, so once you have python, you want to get the latest version of pip working:

$ python -m ensurepip --upgrade

[first make sure that python gives you the one you want. You may need to call python3 instead]

It should download and install the latest pip.

You can now use pip to install other packages.

Using pip:¶

To use pip to install a package, you invoke it with this command:

python -m pip install the_name_of_the_package

Where python is the command you use to invoke the python you want to use (could be python3)

NOTE: You will frequently see advice to use pip like so:

$ pip install something_or_other

Which often works, but also can invoke the wrong version of pip. The above command:

$ python -m pip install something_or_other

calls python, and tells it to run the pip module. It is exactly the same as calling pip directly, except that you are assured that you are getting the version of pip connected the version of python that you are running.

iPython¶

One package we are going to use in class is iPython. YOu can install it with pip like so:

$ python3 -m pip install ipython[all]

You should now be able to run iPython:

$ ipython
Python 3.5.2 (v3.5.2:4def2a2901a5, Jun 26 2016, 10:47:25)
Type "copyright", "credits" or "license" for more information.

IPython 5.1.0 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

git¶

git is a source code version control system. It is not strickly related to Python, but it (or a similar system) is a critical tool for software development in general, and it is very widely used in the Python community. We will be using it, along with the gitHub service, in the program to hand in assignments and support code review.

You need a git client – the gitHub GUI client may be nice – I honestly don’t know, but we will be using the command line client in class.

There are a couple options for a command line client.

This one:

http://sourceforge.net/projects/git-osx-installer/

Is a big download and install, but has everything you need out of the box.

NOTE: if you get a warning like:

”... can’t be opend because it is from an untrusted developer”

you’ll need to go to system preferences:

“Security and Privacy”

Then check the box saying “Open Anyway”. Or maybe check the box saying you can install untrused pacakges – depends on the OS-X version.

This one:

http://git-scm.com/download/mac

Works great, but you need the XCode command line tools to run it. If you already have that, or expect to need a compiler anyway, then this is a good option.

You can get XCode from the Apple App Store.

(If you try running “git” on the command line after installing, it should send you there).

Warning: XCode is a BIG download. Once installed, run it so it can initialize itself.

After either of these is installed, the git command should work:

$ git --version
git version 1.9.5 (Apple Git-50.3)