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- Installation

# Installation

## Requirements

Astropy has the following strict requirements:

- Python 2.6, 2.7, 3.1 or 3.2
- Numpy 1.5.0 or later

Astropy also depends on other packages for optional features:

- h5py: To read/write `Table` objects from/to HDF5 files
- scipy: To power a variety of features (currently mainly cosmology-related functionality)
- xmllint: To validate VOTABLE XML files.

However, note that these only need to be installed if those particular features are needed. Astropy will import even if these dependencies are not installed.

## Installing Astropy

### Using `pip`

To install Astropy with `pip`, simply run:

    pip install --no-deps astropy

Warning

Users of the Anaconda python distribution should follow the instructions for Anaconda python distribution.

Note

You will need a C compiler (e.g. `gcc` or `clang`) to be installed (see Building from source below) for the installation to succeed.

Note

The `--no-deps` flag is optional, but highly recommended if you already have Numpy installed, since otherwise pip will sometimes try to “help” you by upgrading your Numpy installation, which may not always be desired.

Note

If you get a `PermissionError` this means that you do not have the required administrative access to install new packages to your Python installation. In this case you may consider using the `--user` option to install the package into your home directory. You can read more about how to do this in the pip documentation.

Alternatively, if you intend to do development on other software that uses Astropy, such as an affiliated package, consider installing Astropy into a virtualenv.

Do not install Astropy or other third-party packages using `sudo` unless you are fully aware of the risks.

### Anaconda python distribution

Astropy is installed by default with Anaconda. To update to the latest version run:

    conda update astropy

Note

There may be a delay of a day or to between when a new version of Astropy is released and when a package is available for Anaconda. You can check for the list of available versions with `conda search astropy`.

Note

Attempting to use `pip` to upgrade your installation of Astropy may result in a corrupted installation.

### Binary installers

Binary installers are available on Windows for Python 2.6, 2.7, 3.1, and 3.2 at PyPI.

### Testing an installed Astropy

The easiest way to test your installed version of astropy is running correctly is to use the `astropy.test()` function:

    import astropy
    astropy.test()

The tests should run and print out any failures, which you can report at the Astropy issue tracker.

Note

This way of running the tests may not work if you do it in the astropy source distribution. See Testing a source code build of Astropy for how to run the tests from the source code directory, or Running Tests for more details.

## Building from source

### Prerequisites

You will need a compiler suite and the development headers for Python and Numpy in order to build Astropy. On Linux, using the package manager for your distribution will usually be the easiest route, while on MacOS X you will need the XCode command line tools.

The instructions for building Numpy from source are also a good resource for setting up your environment to build Python packages.

You will also need Cython installed to build from source, unless you are installing a numbered release. (The releases packages have the necessary C files packaged with them, and hence do not require Cython.)

Note

If you are using MacOS X, you will need to the XCode command line tools. One way to get them is to install XCode. If you are using OS X 10.7 (Lion) or later, you must also explicitly install the command line tools. You can do this by opening the XCode application, going to Preferences, then Downloads, and then under Components, click on the Install button to the right of Command Line Tools. Alternatively, on 10.7 (Lion) or later, you do not need to install XCode, you can download just the command line tools from https://developer.apple.com/downloads/index.action (requires an Apple developer account).

### Obtaining the source packages

#### Source packages

The latest stable source package for Astropy can be downloaded here.

#### Development repository

The latest development version of Astropy can be cloned from github using this command:

    git clone git://github.com/astropy/astropy.git

Note

If you wish to participate in the development of Astropy, see Developer Documentation. This document covers only the basics necessary to install Astropy.

### Building and Installing

Astropy uses the Python distutils framework for building and installing and requires the distribute extension–the later is automatically downloaded when running `python setup.py` if it is not already provided by your system.

If Numpy is not already installed in your Python environment, the astropy setup process will try to download and install it before continuing to install astropy.

To build Astropy (from the root of the source tree):

    python setup.py build

To install Astropy (from the root of the source tree):

    python setup.py install

### Troubleshooting

If you get an error mentioning that you do not have the correct permissions to install Astropy into the default `site-packages` directory, you can try installing with:

    python setup.py install --user

which will install into a default directory in your home directory.

#### External C libraries

The Astropy source ships with the C source code of a number of libraries. By default, these internal copies are used to build Astropy. However, if you wish to use the system-wide installation of one of those libraries, you can pass one or more of the `--use-system-X` flags to the `setup.py build` command.

For example, to build Astropy using the system `libexpat`, use:

    python setup.py build --use-system-expat

To build using all of the system libraries, use:

    python setup.py build --use-system-libraries

To see which system libraries Astropy knows how to build against, use:

    python setup.py build --help

As with all distutils commandline options, they may also be provided in a `setup.cfg` in the same directory as `setup.py`. For example, to use the system `libexpat`, add the following to the `setup.cfg` file:

    [build]
    use_system_expat=1

#### The required version of setuptools is not available

If upon running the `setup.py` script you get a message like

> The required version of setuptools (>=0.9.8) is not available, and can’t be installed while this script is running. Please install a more recent version first, using ‘easy_install -U setuptools’.

> (Currently using setuptools 0.6c11 (/path/to/setuptools-0.6c11-py2.7.egg))

this is because you have a very outdated version of the `setuptools` package which is used to install Python packages. Normally Astropy will bootstrap a newer version of setuptools via the network, but setuptools suggests that you first uninstall the old version (the `easy_install -U setuptools` command). However, in the likely case that your version of setuptools was installed by an OS system package (on Linux check your package manager like apt or yum for a package called `python-setuptools` to be user). In this case trying to uninstall with `easy_install` and without using `sudo` may not work, or may leave your system package in an inconsistent state.

As the best course of action at this point depends largely on the individual system and how it is configured, if you are not sure yourself what do please ask on the Astropy mailing list.

#### The Windows installer can’t find Python in the registry

This is a common issue with Windows installers for Python packages that do not support the new User Access Control (UAC) framework added in Windows Vista and later. In particular, when a Python is installed “for all users” (as opposed to for a single user) it adds entries for that Python installation under the `HKEY_LOCAL_MACHINE` (HKLM) hierarchy and not under the `HKEY_CURRENT_USER` (HKCU) hierarchy. However, depending on your UAC settings, if the Astropy installer is not executed with elevated privileges it will not be able to check in HKLM for the required information about your Python installation.

In short: If you encounter this problem it’s because you need the appropriate entries in the Windows registry for Python. You can download this script and execute it with the same Python as the one you want to install Astropy into. For example to add the missing registry entries to your Python 2.7:

    C:\>C:\Python27\python.exe C:\Path\To\Downloads\win_register_python.py

### Building documentation

Note

Building the documentation is in general not necessary unless you are writing new documentation or do not have internet access, because the latest (and archive) versions of astropy’s documentation should be available at docs.astropy.org .

Building the documentation requires the Astropy source code and some additional packages:

> - Sphinx (and its dependencies) 1.0 or later
> - Graphviz

Note

Sphinx also requires a reasonably modern LaTeX installation to render equations. Per the Sphinx documentation, for the TexLive distribution the following packages are required to be installed:

- latex-recommended
- latex-extra
- fonts-recommended

For other LaTeX distributions your mileage may vary. To build the PDF documentation using LaTeX, the `fonts-extra` TexLive package or the `inconsolata` CTAN package are also required.

There are two ways to build the Astropy documentation. The most straightforward way is to execute the command (from the astropy source directory):

    python setup.py build_sphinx

The documentation will be built in the `docs/_build/html` directory, and can be read by pointing a web browser to `docs/_build/html/index.html`.

The LaTeX documentation can be generated by using the command:

    python setup.py build_sphinx -b latex

The LaTeX file `Astropy.tex` will be created in the `docs/_build/latex` directory, and can be compiled using `pdflatex`.

The above method builds the API documentation from the source code. Alternatively, you can do:

    cd docs
    make html

And the documentation will be generated in the same location, but using the installed version of Astropy.

### Testing a source code build of Astropy

The easiest way to test that your Astropy built correctly (without installing astropy) is to run this from the root of the source tree:

    python setup.py test

There are also alternative methods of Running Tests.