README.md

Package managers

As you learn more about coding, you will find yourself having to install and uninstall hundreds to thousands of small programs, called "packages" or "libraries". If you install these the same way you install programs like MS Office (e.g. download executable and run), you will overwhelm yourself very quickly. Luckily, package managers exist.

###You already use package managers!

Have you ever installed an app on your phone, or a game through steam? If you have, then you already use package managers.

Let's think through some of the advantages:

• Centralized searching
• One-click install and uninstall processes
• Automatically installs the right version for your device
• Easy to view all installed packages and versions
• One-click "update all" functionality

Code package managers do all of this for you - and more! We'll focus on the basic features here, but you should take the time to read up on the more advanced topics when you get a chance.

###Any caveats?

While there has been a push to have only one package manager that controls everything, the current state of programming is more divided. Most programming languages come with their own specialized package managers, and each operating system additionally has its own package manager. This means that you will probably have a couple of package managers to handle. This is not as simple as one manager, but it is still much better than installing everything manually. It's no different than having to manage separate App Store, Google Play, and Steam accounts.

Furthermore, not all packages are guaranteed to work through every package manager. It's up to the package authors to determine which managers to support or ignore. Large projects generally support everything, but small domain-specific packages (like those commonly used in science) rarely support every (or any) package manager. Resist the urge to give up when things get tough!

###Package managers you should know

Below, we will break package managers into language-specific and OS-specific. Wherever possible, We're providing you the most popular way to do things without getting too much into the why. From here, we'll install a package manager and walk through its features.

#####Platform-specific package managers

These are package managers that are only available on one operating system. These usually involve packages that need to be compiled, so expect to see a lot of Fortran, C, and C++ libraries.

• Linux: apt-get for Debian, yum for Red Hat, and more. Installed by default.
• Mac: Homebrew is the current standard.
• Windows: Chocolatey is fairly popular.

#####Language-specific package managers

Many other languages come with their own cross-platform package managers. It's generally recommended to use these over platform-specific managers when possible.

• Go: get
• Julia: Pkg
• Rust: cargo
• Ruby: gem
• R: install.packages
• Python: pip

#####Conda

Conda is a package manager developed for scientists. It's not platform specific, but it's not really language specific either. Features include:

• Cross platform
• No root access required (great for older clusters!)
• Python centric, but handles C, Fortran, R, and more
• Uses pre-compiled packages for super-fast installs
• Supports pip packages
• Easy to swap programming language versions (e.g. Python 2 vs 3)

Conda is 1. interesting and 2. won't mess up your environment. In other words, it's a great workshop package manager. Let's install it and see how it works.

###Workshop - installing conda

• Go to this site and download the Python 3 version for your OS.
• Run it by either double-clicking or typing bash Miniconda-*.sh.
• Make sure to select "yes" for every option.
• To test, reboot your terminal and type which python. It should point to ~/miniconda3/bin/python.

We can now use conda to install, uninstall, and upgrade packages in one-line commands. Let's grab a couple of the most commonly used Python packages: numpy, ipython, and flake8. To install all of these packages, run the command:

conda install numpy ipython flake8

You should now be able to type ipython to enter an IPython terminal, import numpy to use numpy's linked fortran libraries, and flake8 to test your code against a style guide.

Let's go back to our above list of package manager benefits, and show how we would use conda in each scenario.

#####Centralized searching

conda search django will search for all packages with "django" in the name.

#####One-click install and uninstall processes

conda install django installs the Django web framework. conda remove django removes it.

#####Automatically installs the right version for your device

When you typed conda install django, it grabbed the most recent version that works with your OS, architecture, and python version. Much like google play, it did it all without you noticing.

#####Easy to view all installed packages and versions

conda list. Pretty straightforward.

#####One-click "update all" functionality

conda update --all will go through every installed package, check for newer versions, and update when needed.

###Moving forward

This is as far as we're going with package managers. Spend some time getting comfortable with their basic usage, and then dive into the more advanced features. Look into two topics in particular:

• Virtual environments provide another layer of organization, and are especially useful if you have multiple simultaneous projects. Here's a conda tutorial.
• Making your projects installable through package managers. It's a good practice that allows you to easily share your project with others. Here's a pip tutorial.
• For every language you use, read through the most installed packages. It's a good way to learn what's out there. Here's a list for python.