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Overview
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Here we describe a broad overview of the Astropy project and its parts.

Astropy Project Concept
=======================

The "Astropy Project" is distinct from the `astropy` package. The
Astropy Project is a process intended to facilitate communication and
interoperability of python packages/codes in astronomy and astrophysics.
The project thus encompasses the `astropy` core package (which provides a
common framework), all "affiliated packages" (described below in
`Affiliated Packages`), and a general community aimed at bringing
resources together and not duplicating efforts.


`astropy` Core Package
======================

The `astropy` package (alternatively known as the "core" package)
contains various classes, utilities, and a packaging framework intended
to provide commonly-used astronomy tools. It is divided into a variety of
sub-packages, which are documented in the remainder of this
documentation (see :ref:`user-docs` for documentation of these components).

The core also provides this documentation, and a variety of utilities
that simplify starting other python astronomy/astrophysics packages. As
described in the following section, these simplify the process of
creating affiliated packages.


Affiliated Packages
===================

The Astropy project includes the concept of "affiliated packages." An
affiliated package is an astronomy-related python package that is not
part of the `astropy` core source code, but has requested to be included
in the Astropy project. Such a package may be a candidate for eventual
inclusion in the main `astropy` package (although this is not required).

There is a registry of affiliated packages at
http://affiliated.astropy.org, and in the near future, the `astropy` core
will include a tool to install affiliated packages by name. See the
:mod:`~astropy.config` module documentation for details about the
affiliated package registry and install tool. Note that affiliated
packages do not use the `astropy` namespace, which is reserved for the
core. Instead, they either use their package name directly, or
`awastropy.packagename` ("affiliated with astropy").

If you are interested in starting an affiliated package, or have a
package you are interested in making more compatible with astropy, the
`astropy` core package includes a variety of features that simplify and
homogenize package management. Astropy provides a `package template
<http://github.com/astropy/package-template>`_ that provides a common
way to organize packages, to make your life simpler. You can use this
template either with a new package you are starting or an existing
package to make it more compatible with Astropy and the affiliated
package installer. See the `usage instructions in the template
<https://github.com/astropy/package-template/blob/master/README.rst>`_
for further details.


Community
=========

Aside from the actual code, Astropy is also a community of
astronomy-associated users and developers that agree that sharing utilities
is healthy for the community and the science it produces. This community
is of course central to accomplishing anything with the code itself.