Unidata Online Python Training

Learning Python for the Atmospheric Sciences at your own pace

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Getting Going with Python on Mac OS X

The aim of this web page is to help you get started with Python on Mac OS X. We will explain what a package management tool is, how to download conda package management tool via the Anaconda installer, and guide you on the OS X Terminal application so that you can use conda from the command line. Finally, we will wrap up by installing one library with conda.

What Is a Package Management Tool?

A package management tool is a software application that helps you manage software libraries that enable you to get your work done. These software libraries may relate to plotting for scientific publication or accessing certain kinds of data, for example.

When you start using Python, you will want use software libraries that are not part of the standard Python installation. For example, you may wish to use the Unidata metpy library for meteorological data and visualization. Anaconda from Continuum Analytics will help you install metpy easily.

Installing the conda Package Management Tool

The conda package management tool is part of the Anaconda software package. Install conda by navigating to the Anaconda download page. Scroll down to the “Anaconda for OS X” portion of the web page.

Download the Python 3.5 version by clicking on the “Mac OS X 64 bit Graphical Installer” link. It is a big download, so it is best to be on fast network. Open the installer file you just downloaded. It should be named something like Anaconda[version]-MacOSX-x86_64.pkg.

This action will guide you through the conda installation on your Mac. The second “Read Me” step is important, as the installation will make some modifications that the OS X Terminal application can make use of. We cover the OS X Terminal next.

Anaconda Installer

OS X Terminal Application

The OS X Terminal is a software program that gives you the ability to give text based instructions to your computer. As you make progress in geoscientific programming, you will probably use the Terminal a lot, so it will benefit you to become familiar with it.

For this exercise we will open up the Terminal by going to the OS X Finder and navigating to the Application, Utilities folder. There you will find the Terminal application which you can double click on to launch.

OS X Terminal

In the Terminal application, you will see a character such as $ symbol known as the command line. The command line is where you give text instructions to your computer.

Interacting with conda

Let’s make sure conda is installed by entering this instruction on the command line:

conda list

yields

# packages in environment at /Users/chastang/anaconda:
#
alabaster                 0.7.7                    py35_0  
anaconda                  4.0.0               np110py35_0  
anaconda-client           1.4.0                    py35_0  
...
numexpr                   2.5                 np110py35_0  
numpy                     1.10.4                   py35_0  
odo                       0.4.2                    py35_0  
...
yaml                      0.1.6                         0  
zeromq                    4.1.3                         0  
zlib                      1.2.8                         0

which will list linked packages in a conda environment. You’ll notice libraries such as the scientific computing library numpy that you will probably be making use of.

If You Have Problems with conda list

If conda list worked without trouble, skip this subsection. If that last conda list command gave you an error, it is possible that you are running the wrong flavor of the OS X Terminal (or more precisely the wrong Unix shell). Ensure you are running the bash shell by going to Terminal, Preferences… menu, and verifying that /bin/bash is selected. If you change it, please quit, and restart the Terminal application.

/bin/bash

Getting Our Feet Wet by Installing Metpy with conda

We first have to give conda an instruction on where to find metpy on the conda-forge channel.

conda config --add channels conda-forge

We can now install metpy:

conda install metpy

Let’s verify we installed metpy with the following command:

conda list

should yield amongst other libraries:

# packages in environment at /Users/chastang/anaconda:
#
...
metpy                     0.3.0                    py35_1    conda-forge
...

In Summary

You have just learned how to:

  • Download conda
  • Install conda
  • Installed the metpy library with conda

In future installments of the Unidata Online Python training, we will be using conda to install various libraries.