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. But make sure you have Python 3.7.*

If not, then read on.

Terminal

You will need a command line terminal. The built-in “terminal” application works fine. Find it in:

/Applications/Utilities/Terminal

Drag it to the dock to easily access.

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 we recommend installing an independent installation from python.org:

Download the latest realease of Python (currently 3.7.0) 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. Type this at a terminal prompt:

$ cd /Library/Frameworks/Python.framework/Versions/3.7/bin
$ ln -s python3.7 python

Or an add an alias in your shell by adding the following line:

alias python='python3'

to your .bash_profile file.

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

$ python
Python 3.7.0 (v3.7.0:1bf9cc5093, Jun 26 2018, 23:26:24)
[Clang 6.0 (clang-600.0.57)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>>

This is the Python interpreter.

Type ctrl+D to get out (or exit())

Note

If all this is confusing to you – take heart – you will get used it it. And in the meantime, you can simply type python3 when you want to run python.

pip

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

$ python3 -m ensurepip --upgrade

[python may work too, if you set things up correctly above, but python3 should always work.]

It should download and install the latest pip. Or let you know that you already have it.

You can now use pip to install other packages. The first thing you may want to do is update pip itself:

$ python3 -m pip install --upgrade pip

Using pip:

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

python3 -m pip install the_name_of_the_package

Where python3 is the command you use to invoke the Python you want to use.

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

$ pip install something_or_other

This often works, but also can invoke the wrong version of pip. This command:

$ python3 -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 the program from the beginning is iPython. You can install it with pip like so:

$ python3 -m pip install ipython

(It will install a LOT…).

Now you should now be able to run iPython:

$ ipython
Python 3.7.0 (v3.7.0:1bf9cc5093, Jun 26 2018, 23:26:24)
Type 'copyright', 'credits' or 'license' for more information
IPython 6.5.0 -- An enhanced Interactive Python. Type '?' for help.

In [1]:

Which you can also get out of with ctrl+D or exit()

git

git is a source code version control system. It is not strictly 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. However, we will be using the command line client in class.

There are a couple of options for a command line client.

This option is a big download and install, but has everything you need out of the box:

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

NOTE: if you get a warning like:

“… can’t be opened because it is from an untrusted developer”

you’ll need to go to system preferences:

“Security and Privacy”

Depending on the OS-X version, you will need to check the box saying “Open Anyway,” or perhaps the box saying you can install untrusted packages.

This option works great, but you need the XCode command line tools to run it:

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

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 2.11.0 (Apple Git-81)

Testing it out

To be ready for the program, you need to have, all available from the command line:

• python
• pip
• iPython
• git

To try it out, you should be able to run all of the following commands, and get something like the results shown:

(recall that you can get out of the Python or iPython command lines with ctrl+D)

For Python:

$ python3
Python 3.7.0 (v3.7.0:1bf9cc5093, Jun 26 2018, 23:26:24)
[Clang 6.0 (clang-600.0.57)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>>

For iPython:

$ ipython
Python 3.7.0 (v3.7.0:1bf9cc5093, Jun 26 2018, 23:26:24)
Type 'copyright', 'credits' or 'license' for more information
IPython 6.5.0 -- An enhanced Interactive Python. Type '?' for help.

For pip:

$ python3 -m pip --version
pip 18.0 from /Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pip (python 3.7)

Note that when you ask pip for --version it tells you which version of python it is “connected” to.

For git:

$ git --version
git version 2.15.2 (Apple Git-101.1)