The km3io Python package

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This software provides a set of Python classes to read KM3NeT ROOT files without having ROOT, Jpp or aanet installed. It only depends on Python 3.5+ and the amazing uproot package and gives you access to the data via numpy arrays.

It’s very easy to use and according to the uproot benchmarks, it is able to outperform the ROOT I/O performance.

Note: Beware that this package is in the development phase, so the API will change until version 1.0.0 is released!

Installation

Install km3io using pip:

pip install km3io

To get the latest (stable) development release:

pip install git+https://git.km3net.de/km3py/km3io.git

Reminder: km3io is not dependent on aanet, ROOT or Jpp!

Questions

If you have a question about km3io, please proceed as follows:

  • Read the documentation below.

  • Explore the examples in the documentation.

  • Haven’t you found an answer to your question in the documentation, post a git issue with your question showing us an example of what you have tried first, and what you would like to do.

  • Have you noticed a bug, please post it in a git issue, we appreciate your contribution.

Introduction

Most of km3net data is stored in root files. These root files are created using the KM3NeT Dataformat library A ROOT file created with Jpp is an “online” file and all other software usually produces “offline” files.

km3io is a Python package that provides a set of classes: OnlineReader, OfflineReader and a special class to read gSeaGen files. All of these ROOT files can be read installing any other software like Jpp, aanet or ROOT.

Data in km3io is returned as awkward.Array which is an advance Numpy-like container type to store contiguous data for high performance computations. Such an awkward.Array supports any level of nested arrays and records which can have different lengths, in contrast to Numpy where everything has to be rectangular.

The example is shown below shows the array which contains the dir_z values of each track of the first 4 events. The type 4 * var * float64 means that it has 4 subarrays with variable lengths of type float64:

>>> import km3io
>>> from km3net_testdata import data_path
>>> f = km3io.OfflineReader(data_path("offline/numucc.root"))
>>> f[:4].tracks.dir_z
<Array [[0.213, 0.213, ... 0.229, 0.323]] type='4 * var * float64'>

The same concept applies to everything, including hits, mc_hits, mc_tracks, t_sec etc.

Offline files reader

In general an offline file has two methods to fetch data: the header and the events. Let’s start with the header.

Reading the file header

To read an offline file start with opening it with an OfflineReader:

>>> import km3io
>>> from km3net_testdata import data_path
>>> f = km3io.OfflineReader(data_path("offline/numucc.root"))

Calling the header can be done with:

>>> f.header
<km3io.offline.Header at 0x7fcd81025990>

and provides lazy access. In offline files the header is unique and can be printed

>>> print(f.header)
MC Header:
DAQ(livetime=394)
PDF(i1=4, i2=58)
can(zmin=0, zmax=1027, r=888.4)
can_user: can_user(field_0=0.0, field_1=1027.0, field_2=888.4)
coord_origin(x=0, y=0, z=0)
cut_in(Emin=0, Emax=0, cosTmin=0, cosTmax=0)
cut_nu(Emin=100, Emax=100000000.0, cosTmin=-1, cosTmax=1)
cut_primary(Emin=0, Emax=0, cosTmin=0, cosTmax=0)
cut_seamuon(Emin=0, Emax=0, cosTmin=0, cosTmax=0)
decay: decay(field_0='doesnt', field_1='happen')
detector: NOT
drawing: Volume
genhencut(gDir=2000, Emin=0)
genvol(zmin=0, zmax=1027, r=888.4, volume=2649000000.0, numberOfEvents=100000)
kcut: 2
livetime(numberOfSeconds=0, errorOfSeconds=0)
model(interaction=1, muon=2, scattering=0, numberOfEnergyBins=1, field_4=12)
ngen: 100000.0
norma(primaryFlux=0, numberOfPrimaries=0)
nuflux: nuflux(field_0=0, field_1=3, field_2=0, field_3=0.5, field_4=0.0, field_5=1.0, field_6=3.0)
physics(program='GENHEN', version='7.2-220514', date=181116, time=1138)
seed(program='GENHEN', level=3, iseed=305765867, field_3=0, field_4=0)
simul(program='JSirene', version=11012, date='11/17/18', time=7)
sourcemode: diffuse
spectrum(alpha=-1.4)
start_run(run_id=1)
target: isoscalar
usedetfile: false
xlat_user: 0.63297
xparam: OFF
zed_user: zed_user(field_0=0.0, field_1=3450.0)

To read the values in the header one can call them directly:

>>> f.header.DAQ.livetime
394
>>> f.header.cut_nu.Emin
100
>>> f.header.genvol.numberOfEvents
100000

Reading events

To start reading events call the events method on the file:

>>> f
OfflineReader (10 events)
>>> f.keys()
{'comment', 'det_id', 'flags', 'frame_index', 'hits', 'id', 'index',
'mc_hits', 'mc_id', 'mc_run_id', 'mc_t', 'mc_tracks', 'mc_trks',
'n_hits', 'n_mc_hits', 'n_mc_tracks', 'n_mc_trks', 'n_tracks',
'n_trks', 'overlays', 'run_id', 't_ns', 't_sec', 'tracks',
'trigger_counter', 'trigger_mask', 'trks', 'usr', 'usr_names',
'w', 'w2list', 'w3list'}

Like the online reader lazy access is used. Using <TAB> completion gives an overview of available data. Alternatively the method keys can be used on events and it’s data members containing a structure to see what is available for reading.

Reading the reconstructed values like energy and direction of an event can be done with:

>>> f.events.tracks.E
<Array [[117, 117, 0, 0, 0, ... 0, 0, 0, 0, 0]] type='10 * var * float64'>

Online files reader

km3io is able to read events, summary slices and timeslices. Timeslices are currently only supported with split level of 2 or more, which means that reading L0 timeslices is currently not working (but in progress).

Let’s have a look at some ORCA data (KM3NeT_00000044_00005404.root)

Reading Events

To get a lazy ragged array of the events:

import km3io
f = km3io.OnlineReader("KM3NeT_00000044_00005404.root")

That’s it, we created an object which gives access to all the events, but the relevant data is still not loaded into the memory (lazy access)! Now let’s have a look at the hits data:

>>> f.events
Number of events: 17023
>>> f.events[23].snapshot_hits.tot
array([28, 22, 17, 29,  5, 27, 24, 26, 21, 28, 26, 21, 26, 24, 17, 28, 23,29, 27, 24, 23, 26, 29, 25, 18, 28, 24, 28, 26, 20, 25, 31, 28, 23, 26, 21, 30, 33, 27, 16, 23, 24, 19, 24, 27, 22, 23, 21, 25, 16, 28, 22, 22, 29, 24, 29, 24, 24, 25, 25, 21, 31, 26, 28, 30, 42, 28], dtype=uint8)

The resulting arrays are numpy arrays.

Reading SummarySlices

The following example shows how to access summary slices, in particular the DOM IDs of the slice with the index 23:

>>> f.summaryslices
<km3io.online.SummarySlices at 0x7effcc0e52b0>
>>> f.summaryslices.slices[23].dom_id
array([806451572, 806455814, 806465101, 806483369, 806487219, 806487226,
     806487231, 808432835, 808435278, 808447180, 808447186, 808451904,
     808451907, 808469129, 808472260, 808472265, 808488895, 808488990,
     808489014, 808489117, 808493910, 808946818, 808949744, 808951460,
     808956908, 808959411, 808961448, 808961480, 808961504, 808961655,
     808964815, 808964852, 808964883, 808964908, 808969848, 808969857,
     808972593, 808972598, 808972698, 808974758, 808974773, 808974811,
     808974972, 808976377, 808979567, 808979721, 808979729, 808981510,
     808981523, 808981672, 808981812, 808981864, 808982005, 808982018,
     808982041, 808982066, 808982077, 808982547, 808984711, 808996773,
     808997793, 809006037, 809007627, 809503416, 809521500, 809524432,
     809526097, 809544058, 809544061], dtype=int32)

The .dtype attribute (or in general, <TAB> completion) is useful to find out more about the field structure:

>>> f.summaryslices.headers.dtype
dtype([(' cnt', '<u4'), (' vers', '<u2'), (' cnt2', '<u4'), (' vers2',
'<u2'), (' cnt3', '<u4'), (' vers3', '<u2'), ('detector_id', '<i4'), ('run',
'<i4'), ('frame_index', '<i4'), (' cnt4', '<u4'), (' vers4', '<u2'),
('UTC_seconds', '<u4'), ('UTC_16nanosecondcycles', '<u4')])
>>> f.summaryslices.headers.frame_index
<ChunkedArray [162 163 173 ... 36001 36002 36003] at 0x7effccd4af10>

The resulting array is a ChunkedArray which is an extended version of a numpy array and behaves like one.

Reading Timeslices

Timeslices are split into different streams since 2017 and km3io currently supports everything except L0, i.e. L1, L2 and SN streams. The API is work-in-progress and will be improved in future, however, all the data is already accessible (although in ugly ways ;-)

To access the timeslice data:

>>> f.timeslices
Available timeslice streams: L1, SN
>>> f.timeslices.stream("L1", 24).frames
{806451572: <Table [<Row 1577843> <Row 1577844> ... <Row 1578147>],
 806455814: <Table [<Row 1578148> <Row 1578149> ... <Row 1579446>],
 806465101: <Table [<Row 1579447> <Row 1579448> ... <Row 1580885>],
 ...
}

The frames are represented by a dictionary where the key is the DOM ID and the value a numpy array of hits, with the usual fields to access the PMT channel, time and ToT:

>>> f.timeslices.stream("L1", 24).frames[806451572].dtype
dtype([('pmt', 'u1'), ('tdc', '<u4'), ('tot', 'u1')])
>>> f.timeslices.stream("L1", 24).frames[806451572].tot
array([29, 21,  8, 29, 22, 20,  1, 37, 11, 22, 11, 22, 12, 20, 29, 94, 26,
       26, 18, 16, 13, 22,  6, 29, 24, 30, 14, 26, 12, 23,  4, 25,  6, 27,
        5, 13, 21, 28, 30,  4, 25, 10,  5,  6,  5, 17,  4, 27, 24, 25, 27,
       28, 32,  6,  3, 15,  3, 20, 33, 30, 30, 20, 28,  6,  7,  3, 14, 12,
       25, 27, 26, 25, 22, 21, 23,  6, 20, 21,  4,  4, 10, 24, 29, 12, 30,
        5,  3, 24, 15, 14, 25,  5, 27, 23, 26,  4, 28, 15, 34, 22,  4, 29,
       24, 26, 29, 23, 25, 28, 14, 31, 27, 26, 27, 28, 23, 54,  4, 25, 11,
       28, 25, 24,  7, 27, 28, 28, 18,  3, 13, 14, 38, 28,  4, 21, 16, 16,
        4, 21, 26, 21, 28, 64, 21,  1, 24, 21, 26, 26, 25,  4, 28, 11, 31,
       10, 24, 24, 28, 10,  6,  4, 20, 26, 18,  5, 18, 24,  5, 27, 23, 20,
       29, 20,  6, 18,  5, 24, 17, 28, 24, 15, 26, 27, 25,  9,  3, 18,  3,
       34, 29, 10, 25, 30, 28, 19, 26, 34, 27, 14, 17, 15, 26,  8, 19,  5,
       27, 13,  5, 27, 46,  3, 25, 13, 30,  9, 21, 12,  1, 32, 25,  8, 30,
        4, 24, 11,  3, 11, 27,  5, 13,  5, 16, 18,  3, 22, 10,  7, 32, 29,
       15, 20, 18, 16, 27,  5, 22,  4, 33,  5, 29, 24, 30,  7,  7, 25, 33,
        7, 20,  8, 30,  4,  4,  6, 26,  8, 24, 22, 12,  6,  3, 21, 28, 11,
       24, 27, 27,  6, 29,  5, 18, 11, 26,  5, 19, 32, 25,  4, 20, 35, 30,
        5,  3, 26, 30, 23, 28,  6, 25, 25,  5, 45, 23, 18, 29, 28, 23],
      dtype=uint8)

Indices and tables