Last modified: October 2018

AHELP for CIAO 4.12


Context: scripting


Python is a dynamic object-oriented programming language used by CIAO


Python is a dynamic object-oriented programming language that can be used for many kinds of software development. It offers strong support for integration with other languages and tools and comes with extensive standard libraries. A list of key software features is available on the About Python webpage.

Refer to the Python Programming Language website for more information. Several web sites dedicated to using Python for Astronomical research exist, including AstroPython

Python in CIAO

The CIAO software offers Python as the user scripting environment. Python is distributed with CIAO, but users may opt to run their own custom installation instead; see "ahelp ciaorc" for information on how to change the Python version that is being used.

For more information, refer to the Scripting in CIAO webpages.

Python package Versions

The following versions are provided with CIAO 4.11:

Installing extra Python packages

The CIAO 4.11 release includes - as a beta release - the pip tool for installing Python packages into the CIAO installation. For users who have write permission to the CIAO installation (e.g. they have installed CIAO onto their own machine), a package such as AstroPy can be installed (after initializing CIAO) with the command:

unix% pip3 install astropy

or - if they don't have write permission to the CIAO installation , or do not want to risk the installation - the following will install it locally:

unix% pip3 install --user astropy

Listing installed packages

The list option can be used to see what Python packages are available:

unix% pip3 list --format=columns

Please contact the CXC HelpDesk if you encounter problems when using pip3.

Jupyter notebook support

CIAO 4.11 includes support for Jupyter notebooks, so after starting CIAO, the following command will start the server, and open a browser window, for the contents of the notebooks directory:

unix% jupyter notebook --notebook-dir notebooks

Since most CIAO tools are run from the command line, it may be useful to also install the bash kernel for Jupyter notebooks, using:

unix% pip3 install bash_kernel
unix% python -m bash_kernel.install

This will let users select a "bash kernel" for running commands within a notebook.

Changes in CIAO 4.11

Python 3.5 only

The CIAO 4.11 release only supports Python 3.5, as support for Python 2.7 has been dropped. The installation includes the six Python compatability library, which may be helpful in quickly converting code from Python 2.7 to 3.5.

Updated Python packages

The extra Python software provided with CIAO - namely IPython and NumPy - has been updated. This includes adding support for Jupyter notebooks.

New Python packages

CIAO 4.11 is the first release to include the Matplotlib plotting library. Sherpa can be set up so that it uses Matplotlib rather than ChIPS for its plotting, as described in ahelp sherpa. This release is also the first to include the pip tool for installing Python packages.