.. _overview:

********
Overview
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Packages
========


What is a “package”?
--------------------

* In a broad sense, anything you install using your package manager

* Some kinds of packages have implied behavior and requirements

* Unfortunate overloading: python “package”: a folder that python imports


Package Managers and Repos
--------------------------

* Many package managers: some OS specific:

  - apt, yum, dnf, chocolatey, homebrew, etc.

* Some language specific:

  -  NPM, pip, RubyGems

* And there are many online repositories of packages:

  - PyPI, anaconda.org, CRAN, CPAN

But they all contain:

* Some form of dependency management

* Artifact and/or source repository

The idea is that you install something, and have it *just work*.


Package types:
--------------

A package can be essentially in two forms:

* source
* binary

.. nextslide::

Focusing now on the Python world:

As Python is a dynamic language, this distinction can get a bit blurred:

There is little difference between a source and binary package *for a pure python package*

But if there is any compiled code in there, building from source can be a challenge:

 - Binary packages are very helpful

Source Packages
---------------

A source package is all the source code required to build the package.

Package managers (like pip) can automatically build your package from source.

**But:**

 - Your system needs the correct tools installed, compilers, build tools, etc
 - You need to have the dependencies available
 - Sometimes it takes time, sometimes a LONG time


Binary Packages
---------------

A collection of code all ready to run.

 - Everything is already compiled and ready to go -- makes it easy.

**But:**

 - It's likely to be platform dependent
 - May require dependencies to be installed

How do you manage that if the dependencies aren't in the same language/system?


Python Packaging
----------------

There are two package managers widely used for Python.

**pip:** The "official" solution.

    - Pulls packages from PyPI

    - Handles both source and binary packages (wheels)

    - Python only

.. nextslide::

**conda:** Widely used in the scipy community.

    - Pulls packages from anaconda.org

    - Binary only (does not compile code when installing)

    - Supports other languages / libraries: C, Fortran, R, Perl, Java (anything, really)

    - Manages Python itself!

OS package managers:
--------------------

* Linux: apt, conda, dnf, homebrew, nix, pacman, spack, yum

* OS-X: conda, homebrew, macports, spack

* Windows: chocolatey, conda, cygwin, pacman (msys2)

Sometimes handle python packages -- but we won't talk about those here.