eventio 0.9.2

Python read-only implementation of the EventIO file format

A Python (read-only) implementation of the EventIO data format invented by Konrad Bernloehr as used for example by the IACT extension for CORSIKA: https://www.ikp.kit.edu/corsika

Documentation of the file format: https://www.mpi-hd.mpg.de/hfm/~bernlohr/sim_telarray/Documentation/eventio_en.pdf

Most blocks of the IACT extension and SimTel are implemented. The following blocks are known, but reading their data is not (yet) implemented:

Code	Description
1206	IACT Layout
1207	IACT Trigger Time
2017	SimTel PixelCalib
2024	SimTel RunStat
2025	SimTel MC_RunStat
2028	SimTel CalibEvent

install with

pip install eventio

Open a file produced by the IACT CORSIKA extension

First Example

One may iterate over an instance of IACTFile class in order to retrieve events. Events have a small number of fields. The most important one is the photon_bunches field, which is dictionary mapping telescope ids to a simple structured np.array, containing the typical parameters Cherenkov photon bunches in CORSIKA have, like:

• x, y coordinate in the observation plane (in cm)

• direction cosine cx, cy in x and y direction of the incident angle of the photon

• wavelength lambda of the photon (in nm)

• number of photons associated with this bunch

• the time since the first interaction (in ns, I believe)

• the production height of the photon bunch (called zem)

• a bool flag, whether the photon was scattered in the atmosphere

An event has the following attributes: * header: a namedtuple containing the Corsika Event Header data * end_block: a numpy array containing the Corsika Event End data * time_offset, x_offset, y_offsett, the offset of the array

This prints energy and the number of photons for the first telescope in every event:

import eventio

with eventio.IACTFile('eventio/resources/one_shower.dat') as f:
    for event in f:
        print(event.header.total_energy)
        print(event.photon_bunches[0]['photons'].sum())

Second Example

If you like to plot the origin of the Cherenkov photons of the first event in file eventio/resources/one_shower.data for the first telescope, have a look into this example

It might look similar to this picture:

an example shower

Open a file produced by simtel_array

import eventio

with eventio.SimTelFile('eventio/resources/gamma_test.simtel.gz') as f:

    print(len(f.telescope_descriptions))
    for array_event in f:
        print(array_event['mc_shower']['energy'])

Commandline Tools

We provide three commandline tools, to look into eventio files.

To get an overview over the structure of a file, use eventio_print_structure, for larger files, you might want to pipe its output into e.g. less:

$ eventio_print_structure eventio/resources/gamma_test.simtel.gz
History[70](size=11960, only_subobjects=True, first_byte=16)
    HistoryCommandLine[71](size=668, only_subobjects=False, first_byte=12)
    HistoryConfig[72](size=120, only_subobjects=False, first_byte=692)
    HistoryConfig[72](size=172, only_subobjects=False, first_byte=824)
    HistoryConfig[72](size=180, only_subobjects=False, first_byte=1008)
    HistoryConfig[72](size=176, only_subobjects=False, first_byte=1200)
    HistoryConfig[72](size=72, only_subobjects=False, first_byte=1388)
    And 124 objects more of the same type
    .
    .
    .

To get table of all object versions and counts in a file, use eventio_print_object_information, it can also print json if given the --json option

$ eventio_print_object_information eventio/resources/gamma_test.simtel.gz
 Type | Version | #Objects
--------------------------
   70 |       1 |        3
   71 |       1 |        3
   72 |       1 |    32840
 1212 |       0 |        2
 2000 |       2 |        1
 2001 |       4 |        2
 2002 |       2 |       98
 2002 |       3 |       28
 2003 |       1 |      126
 2004 |       2 |      126
 2005 |       0 |      126
 2006 |       0 |      126
 2007 |       0 |      126
 2008 |       0 |      126
 2009 |       2 |       10
.
.
.

To plot histograms stored in an eventio file (Type 100), use eventio_plot_histograms.

$ eventio_plot_histograms gamma_20deg_180deg_run99___cta-prod3_desert-2150m-Paranal-merged_cone10.simtel.gz

Histogram of Impact distance vs log10(E / TeV)

Low level access

For more low level access to the items of an EventIO file (or to implement a higher level abstraction like IACTFile) one can use the EventIOFile class which gives access to the objects and subobjects in EventIO files.

This is how our test file looks like in the low level view:

In [3]: with EventIOFile('eventio/resources/one_shower.dat') as f:
   ...:     for obj in f:
   ...:         print(obj)
   ...:         if obj.header.only_subobjects:
   ...:             for subobj in obj:
   ...:                 print('   ', subobj)
CORSIKARunHeader[1200](size=1096, only_subobjects=False, first_byte=16)
CORSIKAInputCard[1212](size=448, only_subobjects=False, first_byte=1128)
CORSIKATelescopeDefinition[1201](size=20, only_subobjects=False, first_byte=1592)
CORSIKAEventHeader[1202](size=1096, only_subobjects=False, first_byte=1628)
CORSIKAArrayOffsets[1203](size=16, only_subobjects=False, first_byte=2740)
CORSIKATelescopeData[1204](size=6136, only_subobjects=True, first_byte=2772)
    IACTPhotons(length=6124, n_bunches=382)
CORSIKAEventEndBlock[1209](size=1096, only_subobjects=False, first_byte=8924)
CORSIKARunEndBlock[1210](size=16, only_subobjects=False, first_byte=10036)