Usage examples

Note

These scripts give some quick syntax examples. See also the Tutorial notebooks, for a step-by-step introduction to using voevent-parse and working with XML data.

Basic data access and manipulation

You can also download this example or view it on Github.

#!/usr/bin/python
"""A quick usage example.

Once voeventparse is installed, this should tell you most of what you need to know
in order to start doing things with VOEvent packets.

The attributes are built from the structure of the XML file,
so the best way to understand where the variable names come from is to simply
open the XML packet in your favourite web browser and dig around.

See also:
* lxml documentation at http://lxml.de/objectify.html
* VOEvent standard at http://www.ivoa.net/documents/VOEvent/
* VOEvent schema file at http://www.ivoa.net/xml/VOEvent/VOEvent-v2.0.xsd
"""
from __future__ import print_function
import copy
import voeventparse
from voeventparse.tests.resources.datapaths import swift_bat_grb_pos_v2
import pprint

pp = pprint.PrettyPrinter()

with open(swift_bat_grb_pos_v2, 'rb') as f:
    v = voeventparse.load(f)

# Basic attribute access
print("Ivorn:", v.attrib['ivorn'])
print("Role:", v.attrib['role'])
print("AuthorIVORN:", v.Who.AuthorIVORN)
print("Short name:", v.Who.Author.shortName)
print("Contact:", v.Who.Author.contactEmail)

# Copying by value, and validation:
print("Original valid as v2.0? ", voeventparse.valid_as_v2_0(v))
v_copy = copy.copy(v)
print("Copy valid? ", voeventparse.valid_as_v2_0(v_copy))

# Changing values:
v_copy.Who.Author.shortName = 'BillyBob'
v_copy.attrib['role'] = voeventparse.definitions.roles.test
print("Changes valid? ", voeventparse.valid_as_v2_0(v_copy))

v_copy.attrib['role'] = 'flying circus'
print("How about now? ", voeventparse.valid_as_v2_0(v_copy))
print("But the original is ok, because we copied? ",
      voeventparse.valid_as_v2_0(v))

v.Who.BadPath = "This new attribute certainly won't conform with the schema."
assert voeventparse.valid_as_v2_0(v) == False
del v.Who.BadPath
assert voeventparse.valid_as_v2_0(v) == True
#######################################################
# And now, SCIENCE
#######################################################
c = voeventparse.get_event_position(v)
print("Coords:", c)
print()
toplevel_params = voeventparse.get_toplevel_params(v)

# print("Toplevel Params:")
# pp.pprint(toplevel_params.items())
print("Trigger ID:", toplevel_params['TrigID']['value'])
grouped_params = voeventparse.get_grouped_params(v)
# pp.pprint(grouped_params.allitems())
print(
"GRB Identified:", grouped_params['Solution_Status']['GRB_Identified']['value'])

Author a new VOEvent packet

You can also download this example or view it on Github.

#!/usr/bin/python
from __future__ import print_function

import datetime
import os

import pytz
import voeventparse as vp

# Set the basic packet ID and Author details

v = vp.Voevent(stream='astronomy.physics.science.org/super_exciting_events',
               stream_id=123, role=vp.definitions.roles.test)

vp.set_who(v, date=datetime.datetime.utcnow(),
           author_ivorn="voevent.4pisky.org")

vp.set_author(v, title="4PiSky Testing Node",
              shortName="Tim"
              )

# Now create some Parameters for entry in the 'What' section.

# Strictly speaking, parameter values should be strings,
# with a manually specified dataType; one of
# `string` (default), `int` , or `float`.
# e.g.
int_flux = vp.Param(name='int_flux',
                    value="2.0e-3",
                    unit='Janskys',
                    ucd='em.radio.100-200MHz',
                    dataType='float',
                    ac=False)
int_flux.Description = 'Integrated Flux'

# But with ac=True (autoconvert) we switch on some magic to take care
# of this for us automatically.
# See ``Param`` docstring for details.
p_flux = vp.Param(name='peak_flux',
                  value=1.5e-3,
                  unit='Janskys',
                  ucd='em.radio.100-200MHz',
                  ac=True
                  )
p_flux.Description = 'Peak Flux'

v.What.append(vp.Group(params=[p_flux, int_flux], name='source_flux'))

# Note ac=True (autoconvert) is the default setting if dataType=None (the default)
amb_temp = vp.Param(name="amb_temp",
                    value=15.5,
                    unit='degrees',
                    ucd='phys.temperature')

amb_temp.Description = "Ambient temperature at telescope"
v.What.append(amb_temp)

# Now we set the sky location of our event:
vp.add_where_when(v,
                  coords=vp.Position2D(ra=123.5, dec=45, err=0.1,
                                       units='deg',
                                       system=vp.definitions.sky_coord_system.utc_fk5_geo),
                  obs_time=datetime.datetime(2013, 1, 31, 12, 5, 30,
                                             tzinfo=pytz.utc),
                  observatory_location=vp.definitions.observatory_location.geosurface)

# Prettyprint some sections for desk-checking:
print("\n***Here is your WhereWhen:***\n")
print(vp.prettystr(v.WhereWhen))

print("\n***And your What:***\n")
print(vp.prettystr(v.What))

# You would normally describe or reference your telescope / instrument here:
vp.add_how(v, descriptions='Discovered via 4PiSky',
           references=vp.Reference('http://4pisky.org'))

# The 'Why' section is optional, allows for speculation on probable
# astrophysical cause
vp.add_why(v, importance=0.5,
           inferences=vp.Inference(probability=0.1,
                                   relation='identified',
                                   name='GRB121212A',
                                   concept='process.variation.burst;em.radio')
           )

# We can also cite earlier VOEvents:
vp.add_citations(v,
                 vp.EventIvorn(
                     ivorn='ivo://astronomy.physics.science.org/super_exciting_events#101',
                     cite_type=vp.definitions.cite_types.followup))

# Check everything is schema compliant:
vp.assert_valid_as_v2_0(v)

output_filename = 'new_voevent_example.xml'
with open(output_filename, 'wb') as f:
    vp.dump(v, f)

print("Wrote your voevent to ", os.path.abspath(output_filename))