# Gammapy conda installation¶

If you want to use some Python package together with Gammapy that is not pre-installed as part of that conda environment, you can use conda or pip to install it. To give an example: you could use conda install pandas or pip install astroplan.

# Background information¶

Anaconda is a free scientific Python distribution available on Linux, MacOS and Windows. By default, it is installed into your home directory (or a directory of your choice), so you can install (or easily remove) it on any computer you have access to.

Another big advantage of conda is that is is a binary package manager. This means that no C, C++ or Fortran compiler is needed on your machine, and installation is very fast. Usually it takes about a Gigabyte of disk space, and installation takes a few minutes, the speed depends on your internet download and hard disk write speed.

When installing Anaconda, you get the conda command line tool, which is a package and environment manager. You can install any number of environments, and within a given environment, you can install any number of packages and versions of your choosing. When a new stable version of Gammapy comes out, and you follow these install instructions for that new version again, and you get a new separate environment and can use either the old or the new on, as you like.

What the commands above do is to create a dedicated conda environment for Gammapy, and to install all required and many optional dependencies for Gammapy, with known good versions that we have extensively tested on Linux, MacOS and Windows. You get a reproducible execution environment, anyone installing that environment should get almost identical results on any machine. There are tiny differences (e.g. 0.0001% in flux) due to different floating point precision of the underlying numerics libraries and compilers used for different platforms, especially for the Numpy dependency.

To install the latest Gammapy stable version as well as the most common optional dependencies for Gammapy, first install Anaconda and then run this commands:

conda config --add channels conda-forge --add channels sherpa
conda install gammapy naima sherpa \
scipy matplotlib ipython-notebook \
cython click reproject iminuit


conda update --all
conda update gammapy


Overall conda is a great cross-platform package manager, you can quickly learn how to use it by reading the conda docs.

## Stable version¶

You can install the latest stable version of Gammapy with conda:

conda install -c conda-forge gammapy


or with pip:

python -m pip install gammapy


Gammapy is not yet available in the Linux distributions, i.e. at this time you can’t install it with e.g. apt-get or yum.