scripts - Command line tools¶
Warning
The Gammapy command line interface (CLI) described here is experimental and only supports a small sub-set of the functionality available via the Gammapy Python package. We have added a few sections at the bottom of this page to explain the current Implementation, Limitations and Plan. And since we don’t offer much here yet, at least we describe how you can Write your own CLI.
Introduction¶
Currently, Gammapy is first and foremost a Python package. This means that to use it you have to write a Python script or Jupyter notebook, where you import the functions and classes needed for a given analysis, and then call them, passing parameters to configure the analysis.
We have also have a scripts - High-level interface that provides high-level Python functions for the most common needs present in the analysis process.
That said, for some very commonly used and easy to configure analysis tasks we have implemented a command line interface (CLI). It is automatically installed together with the Gammapy python package.
Execute¶
To execute the Gammapy CLI, type the command gammapy at your terminal shell
(not in Python):
$ gammapy --help
or equivalently, just type this:
$ gammapy
Either way, the command should print some help text to the console and then exit:
$ gammapy
Gammapy command line interface.
Gammapy is a Python package for gamma-ray astronomy.
For further information, see https://gammapy.org/
Options:
--log-level [debug|info|warning|error]
Logging verbosity level
--ignore-warnings Ignore warnings?
--version Print version and exit
-h, --help Show this message and exit.
Commands:
check Run checks for Gammapy
image Analysis - 2D images
info Display information about Gammapy
All CLI functionality for Gammapy is implemented as sub-commands of the main
gammapy command. If a command has sub-commands, they are listed in the help
output. E.g. the help output from gammapy above shows that there is a
sub-command called gammapy image. Actually, gammapy image itself isn’t a
command that does something, but another command group that is used to group
sub-commands:
$ gammapy image
Usage: gammapy image [OPTIONS] COMMAND [ARGS]...
Analysis - 2D images
Options:
-h, --help Show this message and exit.
Commands:
bin Bin events into an image.
fit Fit morphology model to image using Sherpa.
ts Compute TS image.
Finally, gammapy image bin is a proper sub-sub-command that does something,
it doesn’t have any sub-commands itself, just arguments and options. If you call
it without passing the required arguments, you will get an error:
$ gammapy image bin
Usage: gammapy image bin [OPTIONS] EVENT_FILE REFERENCE_FILE OUT_FILE
Error: Missing argument "event_file".
Use --help to see the help text and available options:
$ gammapy image bin --help
Usage: gammapy image bin [OPTIONS] EVENT_FILE REFERENCE_FILE OUT_FILE
Bin events into an image.
You have to give the event, reference and out FITS filename.
Options:
--overwrite Overwrite existing files?
-h, --help Show this message and exit.
So now you know how the Gammapy CLI is structured and how to discover all available sub-commands, arguments and options.
Command not found¶
Usually tools that install Gammapy (e.g. setuptools via python setup.py
install or pip or package managers like conda) will put the
gammapy command line tool in a directory that is on your PATH, and if
you type gammapy the command is found and executed.
However, due to the large number of supported systems (Linux, Mac OS, Windows)
and different ways to install Python packages like Gammapy (e.g. system install,
user install, virtual environments, conda environments) and environments to
launch command line tools like gammapy (e.g. bash, csh, Windows command
prompt, Jupyter, …) it is not unheard of that users have trouble running
gammapy after installing it.
This usually looks like this:
$ gammapy
-bash: gammapy: command not found
If you just installed Gammapy, search the install log for the message
“Installing gammapy script” to see where gammapy was installed, and check
that this location is on your PATH:
echo $PATH
If you don’t manage to figure out where the gammapy command line tool is
installed, you can try calling it like this instead:
$ python -m gammapy
This also has the advantage that it avoids issues where users have multiple
versions of Python and Gammapy installed and accidentally launch one they don’t
want because it comes first on their PATH. For the same reason these days
the recommended way to use e.g. pip is via python -m pip.
If this still doesn’t work, check if you are using the right Python and have Gammapy installed:
$ which python
$ python -c 'import gammapy'
To see more information about your shell environment, these commands might be helpful:
$ python -m site
$ python -m gammapy info
$ echo $PATH
$ conda info -a # if you're using conda
If you’re still stuck or have any question, feel free to ask for help with installation issues on the Gammapy mailing list of Slack any time!
Example¶
Here’s one example what you can do with the Gammapy CLI: use the gammapy image
bin command to create a counts image from a Fermi-LAT event list as well as a
FITS image that serves as a reference geometry (projection, center, binning) for
the counts image we’re creating.
$ gammapy image bin --help
Usage: gammapy image bin [OPTIONS] EVENT_FILE REFERENCE_FILE OUT_FILE
Bin events into an image.
You have to give the event, reference and out FITS filename.
Options:
--overwrite Overwrite existing files?
-h, --help Show this message and exit.
$ gammapy image bin \
$GAMMAPY_DATA/fermi-3fhl-gc/fermi-3fhl-gc-events.fits.gz \
$GAMMAPY_DATA/fermi-3fhl-gc/fermi-3fhl-gc-counts.fits.gz \
out.fits
INFO:gammapy.scripts.image_bin:Executing cli_image_bin
INFO:gammapy.scripts.image_bin:Reading /home/gammapy-data/datasets/fermi-3fhl-gc/fermi-3fhl-gc-events.fits.gz
INFO:gammapy.scripts.image_bin:Reading /home/gammapy-data/datasets/fermi-3fhl-gc/fermi-3fhl-gc-counts.fits.gz
INFO:gammapy.scripts.image_bin:Writing out.fits
If you have the FTOOLS installed or other tools that can work with the files that Gammapy supports, you can of course use them together:
$ ftlist $GAMMAPY_DATA/fermi-3fhl-gc/fermi-3fhl-gc-events.fits.gz H
Name Type Dimensions
---- ---- ----------
HDU 1 Primary Array Null Array
HDU 2 EVENTS BinTable 23 cols x 32843 rows
HDU 3 GTI BinTable 2 cols x 39042 rows
$ ftlist out.fits H
Name Type Dimensions
---- ---- ----------
HDU 1 Primary Array Image Real4(400x200)
$ ds9 out.fits
Reference¶
Here is auto-generated documentation for all available sub-commands, arguments
and options of the gammapy command line interface (CLI).
It’s not very readable at the moment. With the current formatting it’s a bit hard to tell where documentation for a new sub-command starts and what level of subcommand one is looking at for a given heading. Maybe change to one page per sub-command?
gammapy¶
Gammapy command line interface (CLI).
Gammapy is a Python package for gamma-ray astronomy.
Use --help to see available sub-commands, as well as the available
arguments and options for each sub-command.
For further information, see https://gammapy.org/ and https://docs.gammapy.org/
gammapy [OPTIONS] COMMAND [ARGS]...
Options
-
--log-level<log_level>¶ Logging verbosity level.
Options: debug|info|warning|error
-
--ignore-warnings¶ Ignore warnings?
-
--version¶ Print version and exit.
download¶
Download notebooks, scripts and datasets.
tutorials will download versioned folders for the notebooksgammapy-tutorials folder created at the currentnotebooks will download the notebook files used in the tutorialsgammapy-notebooks folder created at the current working directory.scripts will download a collection of example python scriptsgammapy-scripts folder created at the current working directory.datasets will download the datasets used by Gammapy into agammapy-datasets folder created at the current working directory.gammapy download [OPTIONS] COMMAND [ARGS]...
datasets¶
Download datasets
gammapy download datasets [OPTIONS]
Options
-
--src<src>¶ Specific dataset to download.
-
--release<release>¶ Number of release - ex: 0.12
-
--out<out>¶ Path where datasets will be copied. [default: gammapy-datasets]
notebooks¶
Download notebooks
gammapy download notebooks [OPTIONS]
Options
-
--src<src>¶ Specific notebook to download.
-
--out<out>¶ Path where the versioned notebook files will be copied. [default: gammapy-notebooks]
-
--release<release>¶ Number of release - ex: 0.12)
image¶
Analysis - 2D images
gammapy image [OPTIONS] COMMAND [ARGS]...
bin¶
Bin events into an image.
You have to give the event, reference and out FITS filename.
gammapy image bin [OPTIONS] EVENT_FILE REFERENCE_FILE OUT_FILE
Options
-
--overwrite¶ Overwrite existing files?
Arguments
-
EVENT_FILE¶ Required argument
-
REFERENCE_FILE¶ Required argument
-
OUT_FILE¶ Required argument
info¶
Display information about Gammapy
gammapy info [OPTIONS]
Options
-
--system,--no-system¶ Show system info
-
--version,--no-version¶ Show version info
-
--dependencies,--no-dependencies¶ Show dependencies info
-
--envvar,--no-envvar¶ Show environment variables
jupyter¶
Perform a series of actions on Jupyter notebooks.
The chosen action is applied by default for every Jupyter notebook present in the current working directory.
gammapy jupyter [OPTIONS] COMMAND [ARGS]...
Options
-
--src<src>¶ Local folder or Jupyter notebook filename.
Implementation¶
Currently, the command line interface (CLI) of Gammapy is implemented using click to define sub-commands, arguments and options, as well as calling the right function that implements a given sub-command.
We have chosen to implement all functionality via a single command line tool
called gammapy, with each task as a subcommand. The gammapy command line
tool uses the setuptools console_scripts entry point method to automatically
create command line tools when Gammapy is installed.
This means that to be able to use the tools you have to install Gammapy. Although, from the source folder you can still execute it without installing via
$ python -m gammapy
which executes gammapy/__main__.py as a script as explained here.
Another way to install the gammapy command line tool once, but to have it
point at the Gammapy git source folder while you’re hacking on Gammapy is to use
$ python -m pip install --editable .
Either gammapy or python -m gammapy call the
gammapy.scripts.main.cli function, which is a click.Group object. If you
want you can also import and execute it yourself:
>>> from gammapy.scripts.main import cli
>>> type(cli)
click.core.Group
>>> cli()
>>> cli(['--version'])
>>> cli(['image', 'bin', '--help'])
This is what we do to test the CLI, we import gammapy.scripts.main.cli and
run it via gammapy.utils.testing.run_cli and check the return code and
sometimes console output or generated files. Note that this means that all tests
run in a single Python process, we don’t “shell out” and create a subprocess
that calls gammapy from a sub-shell.
This is also how the auto-generated CLI documentation in the Reference
section above was generated: we use the sphinx-click Sphinx extension that
imports and inspects gammapy.scripts.main.cli to find out about all the
available sub-commands and help text / arguments / options. The click.Group
object exposes all information as attributes and methods. To just give one
example:
>>> from gammapy.scripts.main import cli
>>> cli.commands
{'check': <click.core.Group at 0x112107048>,
'image': <click.core.Group at 0x112102e10>,
'info': <click.core.Command at 0x1120bb278>}
If you’re new to Python command line tools or Click, probably setuptools entry
points and click groups seem very complex. And they are, compared to the rest of
Gammapy which is just def and class statements to make functions and
classes, i.e. “normal” Python code. Just know that to use and even work on the
Gammapy CLI you don’t have to understand how it works under the hood, but if you
want to, it’s actually not that complex.
A good path to learn is to start by reading gammapy/__main__.py and gammapy/scripts/main.py and then to look at an example of how a sub-command in Gammapy is implemented and tested, e.g. gammapy/scripts/image_bin.py and gammapy/scripts/tests/test_image_bin.py.
Note how sub-commands are click.Command objects:
>>> from gammapy.scripts.image_bin import cli_image_bin
>>> type(cli_image_bin)
click.core.Command
that are independent and how the main cli is created via cli.add_command
calls in gammapy/scripts/main.py.
Now you have a basic understanding how things work and should be able to work on
Gammapy CLI (e.g. add more functionality to the CLI interface). If you’re
curious to learn how it works in detail, we suggest you read the click docs
and play with the Gammapy cli object in IPython like we did above when
looking at cli.commands, or read and play with the standalone example in the
Write your own CLI section below.
Limitations¶
The current click-based Gammapy CLI is pretty nice, it is very simple to add commands and also documenting and testing them is pretty nice.
However, the current implementation has some issues and limitations. We describe them in this section, and then in the next one discuss more generally the plan and options for the Gammapy high-level (CLI or non-CLI) interface.
- There is no support for in-memory tool chain analysis pipelines.
I mean something lik e.g.
gammapy binfollowed bygammapy fitwithout writing intermediate files and starting the two commands as separate processes. - There is no support for configuring or writing provenance information for commands or command pipelines (i.e. store which commands were executed with which arguments in input config or “workflow” files as well as output result files).
- More generally, we have to see if the separation of Gammapy as a library of “normal” Python functions and classes that can’t be driven by config files or the command line, and then separate functions that represent the CLI is what we want. It means that we have two different ways to use Gammapy in very different ways, and there is duplication and not a nice transition and re-use between the two ways.
More technical issues that can certainly be fixed if we want to stick with the current click-based CLI:
gammapyalways imports all code from all sub-commands, which drags in large fraction ofastropyandgammapywhether it is used or not. This means thatgammapy --helptakes a few seconds, whereas other commands likegit --helpjust take a very small fraction of a second. This can be improved either by optimising import times throughout Astropy and Gammapy in general, or by lazy-loading the subcommands or by delaying imports into the callbacks from the subcommands.- The CLI documentation isn’t nice yet (see the Reference section above). The sphinx-click package that we use isn’t very well-developed or configurable. However, it’s a single Python file that we could just copy into Gammapy and modify and extend to generate documentation in exactly the way we like. E.g. we probably would want to have help text including examples and links to other parts for the Gammapy API and CLI docs that appear nicely on the console as well on in the HTML docs.
Plan¶
The high-level end-user interface for Gammapy follows the recommendations written in PIG 12 - High-level interface, where the command line tools are part of it. The options explored to build the high-level end-user interface for Gammapy were the following:
- Collection of command line tools. Examples: FTOOLs, Fermi ScienceTools, ctools
- Config-file driven analysis. Examples: FermiPy, or the H.E.S.S.-internal HAP
- No special config- or CLI interface, just normal Python functions and classes. Examples: Sherpa and most Python package like e.g. Astropy or scikit-learn.
- Something more fancy that supports tool configuration and running from Python, config files or a CLI using a single implementation. Examples: ctapipe, fact-tools, python-fire
Options 1 and 2 are nice and simple, and they are user-friendly interfaces, and they would allow us to have a stable high-level interface while being able to continue to improve the Gammapy package without breaking user scripts over the coming years.
Their drawback is that they create a second way to use Gammapy, with some users learning and using the more flexible and powerful Python package, and some the simpler to use, but less flexible high-level interface. And note that eventually this second interface will grow into a config file with 100 options (that’s what we have in HAP) or into 10s of CLI tools with in total again 100s of options (see the ctools). However, the Fermi Science tools CLI and Fermipy config interface are examples where the interface size remains at a reasonable level (for users to learn and for developers to implement and maintain) while still exposing everything that most users need.
Options 3 and 4 are similar, in either case the analysis functionality that is available in Gammapy would be written once. Option 3 is what we have now in the Gammapy Python package. Changing to option 4 would mean adding some boilerplate code everywhere (e.g. Python decorators or sub-classing from “tool” base classes like what ctapipe is developing) or relying on the dynamic and inspection features of the Python language offers (see e.g. python-fire), to make it possible to configure and drive analyses not just via Python code, but via some configuration coming either from configuration files (YAML or XML) or command line options.
The chosen solutions were those proposed in Option 2 in a first step, with some extra command-line tools to come in a second step.
In parallel, we can continue to learn and evaluate solutions others have developed. In python-cli-examples I have started an exploration and evaluation of Python CLI packages, namely click, but also cliff and traitlets, and I might take a closer look also at cement and python-fire there. We should also look in detail at what other projects like LSST, JWST, Fermi, ctapipe, and others do concerning configuration and interface of their science tools. Later in 2018 we will need a comprehensive proposal for code organisation and high-level interface for Gammapy. Suggestions or even contributions are welcome any time!
Write your own CLI¶
This section explains how to write your own command line interface (CLI).
We will focus on the command line aspect, and use a very simple example where we
just call gammapy.stats.significance.
From the interactive Python or IPython prompt or from a Jupyter notebook you just import the functionality you need and call it, like this:
>>> from gammapy.stats import significance
>>> significance(n_observed=10, mu_background=4.2, method='lima')
2.3979181291475453
If you imagine that the actual computation involves many lines of code (and not just a one-line function call), and that you need to do this computation frequently, you will probably write a Python script that looks something like this:
# Compute significance for a Poisson count observation
from gammapy.stats import significance
n_observed = 10
mu_background = 4.2
method = 'lima'
s = significance(n_observed, mu_background, method)
print(s)
We have introduced variables that hold the parameters for the analysis and put
them before the computation. Let’s say this script is in a file called
significance.py, then to use it you put the parameters you like and then
execute it via:
$ python significance.py
If you want, you can also put the line #!/usr/bin/env python at the top of
the script, make it executable via chmod +x significance.py and then you’ll
be able to execute it via ./significance.py if you prefer to execute it like
this. This works on Linux and Mac OS, but not on Windows. It is also possible to
omit the .py extension from the filename, i.e. to simply call the file
significance. Either way has some advantages and disadvantages, it’s a
matter of taste. Omitting the .py is nice because users calling the tool
usually don’t care that it’s a Python script, and it’s shorter. But omitting the
.py also means that some advanced users that open up the file in an editor
have a harder time (because the editor might not recognise it as a Python file
and syntax highlight appropriately), or more importantly that importing
functions of classes from that script from other Python files or Jupyter
notebooks is not easily possible, leading some people to rename it or copy &
paste from it. We’re explaining these details, because if you work with
colleagues and share scripts, you’ll encounter the #!/usr/bin/env python and
scripts with and without .py and will need to know how to work with them.
Writing and using such scripts is perfectly fine and a common way to run science
analyses. However, if you use it very frequently it might become annoying to
have to open up and edit the significance.py file every time to use it. In
that case, you can change your script into a command line interface that allows
you to set analysis parameters without having to edit the file, like this:
$ python significance.py --help
Usage: significance.py [OPTIONS] N_OBSERVED MU_BACKGROUND
Compute significance for a Poisson count observation.
The significance is the tail probability to observe N_OBSERVED counts or
more, given a known background level MU_BACKGROUND.
Options:
--method [lima|simple] Significance computation method
--help Show this message and exit.
$ python significance.py 10 4.2
2.39791813
$ python significance.py 10 4.2 --method simple
2.83011021
In Python, there are several ways to do command line argument parsing and to
create command line interfaces. Of course you’re free to do whatever you like,
but if you’re not sure what to use to build your own CLIs, we suggest you give
click a try. Here is how you’d rewrite your significance.py as a click
CLI:
"""Example how to write a command line tool with Click"""
import click
from gammapy.stats import significance
# You can call the callback function for the click command anything you like.
# `cli` is just a commonly used generic term for "command line interface".
@click.command()
@click.argument("n_observed")
@click.argument("mu_background")
@click.option(
"--method",
type=click.Choice(["lima", "simple"]),
default="lima",
help="Significance computation method",
)
def cli(n_observed, mu_background, method):
"""Compute significance for a Poisson count observation.
The significance is the tail probability to observe N_OBSERVED counts
or more, given a known background level MU_BACKGROUND."""
s = significance(n_observed, mu_background, method)
print(s)
if __name__ == "__main__":
cli()
As mentioned above in the Implementation, we use click in
Gammapy itself. We also use click frequently for our own projects if we
choose to add a CLI (no matter if Gammapy is used or not). Putting the CLI in a
file called make.py makes it easy to go back to a project after a while and
to remember or quickly figure out again how it works (as opposed to just having
a bunch of Python scripts or Jupyter notebooks where it’s harder to remember
where to edit parameters and which ones to run in which order). One example is
the gamma-cat make.py.
If you find that you don’t like click, another popular alternative to create
CLIs is argparse from the Python standard library. To learn argparse, either
read the official documentation, or the PYMOTW argparse tutorial. For basic
use cases argparse is similar to click, the main difference being that
click uses decorators (@command, @argument, @option) attached to
a callback function to execute, whereas argparse uses classes and method
calls to create a parser object, and then you have to call parse_args
yourself and also pass the args to the code or function to execute yourself.
So for basic use cases, but also for more advanced use cases where you define a
CLI with sub-commands, argparse can be used just as well, it’s just a little
harder to learn and use than click (of course that’s a matter of opinion).
Another advantage of choosing Click is that once you’ve learned it, you’ll be
able to quickly read and understand, or even contribute to the Gammapy CLI.
Reference/API¶
Besides the CLI interface, the gammapy.scripts package currently contains a
bunch of things that will probably all be removed or rewritten and integrated in
other sub-packages of Gammapy, leaving scripts just as the high-level
command line script interface for Gammapy.