To use Gammapy you need a basic knowledge of Python, Numpy, Astropy, as well as matplotlib for plotting. Many standard gamma-ray analyses can be done with few lines of configuration and code, so you can get pretty far by copy and pasting and adapting the working examples from the Gammapy documentation. But eventually, if you want to script more complex analyses, or inspect analysis results or intermediate analysis products, you need to acquire a basic to intermediate Python skill level.
To learn more about Gammapy, and also for interactive data analysis in general, we recommend you use Jupyter notebooks. Assuming you have followed the steps above to install Gammapy and activate the conda environment, you can start JupyterLab like this:
$ jupyter lab
This should open up JupyterLab app in your web browser, where you can
create new Jupyter notebooks or open up existing ones. If you have downloaded the
gammapy download tutorials, you can browse your
folder with Jupyterlab and execute them there.
If you haven’t used Jupyter before, try typing
print("Hello Jupyter") in the
first input cell, and use the keyboard shortcut
SHIFT + ENTER to execute it.
Gammapy is a Python package, so you can of course import and use it from Python:
$ python Python 3.6.0 | packaged by conda-forge | (default, Feb 10 2017, 07:08:35) [GCC 4.2.1 Compatible Apple LLVM 7.3.0 (clang-703.0.31)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> from gammapy.stats import CashCountsStatistic >>> CashCountsStatistic(n_on=10, mu_bkg=4.2).sqrt_ts 2.397918129147546
IPython is nicer to use for interactive analysis:
$ ipython Python 3.6.0 | packaged by conda-forge | (default, Feb 10 2017, 07:08:35) Type 'copyright', 'credits' or 'license' for more information IPython 6.5.0 -- An enhanced Interactive Python. Type '?' for help. In : from gammapy.stats import CashCountsStatistic In : CashCountsStatistic(n_on=10, mu_bkg=4.2).sqrt_ts Out: array([2.39791813])
For example you can use
? to look up help for any Gammapy function, class or
method from IPython:
In : CashCountsStatistic?
Of course, you can also use the Gammapy online docs if you prefer, clicking in links
gammapy.stats.CashCountsStatistic) or using search docs field in the upper left.
from gammapy.data import DataStore data_store = DataStore.from_dir('$GAMMAPY_DATA/hess-dl3-dr1/') events = data_store.obs(obs_id=23523).events print(events)
EventList --------- <BLANKLINE> Instrument : H.E.S.S. Phase I Telescope : HESS Obs. ID : 23523 <BLANKLINE> Number of events : 7613 Event rate : 4.513 1 / s <BLANKLINE> Time start : 53343.92234009259 Time stop : 53343.94186555556 <BLANKLINE> Min. energy : 2.44e-01 TeV Max. energy : 1.01e+02 TeV Median energy : 9.53e-01 TeV <BLANKLINE> Max. offset : 58.0 deg
Try to make your first plot using the
gammapy.data.EventList.peek helper method:
import matplotlib.pyplot as plt events.peek() plt.savefig("events.png")
Another common way to use Gammapy is to write a Python script.
Try it and put the following code into a file called
"""Example Python script using Gammapy""" from gammapy.data import DataStore data_store = DataStore.from_dir('$GAMMAPY_DATA/hess-dl3-dr1/') events = data_store.obs(obs_id=23523).events print(events.energy.mean())
You can run it with Python:
$ python example.py 4.418007850646973 TeV
If you want to continue with interactive data or results analysis after running some Python code, use IPython like this:
$ ipython -i example.py
For examples how to run Gammapy analyses from Python scripts, see Survey Map Script.