# Licensed under a 3-clause BSD style license - see LICENSE.rst
"""
A module for searching remote source and observation catalogs
A Simple Cone Search (SCS) service allows a client to search for
records in a source or observation catalog whose positions are within
some minimum distance of a search position (i.e. within a specified
"cone" on the sky). This module provides an interface for accessing
such services. It is implemented as a specialization of the DAL Query
interface.
The ``search()`` function provides a simple interface to a service,
returning an SCSResults instance as its results which represents the
matching records from the catalog. The SCSResults supports access to
and iterations over the individual records; these are provided as
SCSRecord instances, which give easy access to key metadata in the
response, including the ICRS position of the matched source or observation.
This module also features the SCSQuery class that provides an
interface for building up and remembering a query. The SCSService
class can represent a specific service available at a URL endpoint.
"""
from pyvo.io.vosi.vodataservice import TableParam
from astropy.coordinates import SkyCoord
from astropy.units import Unit, Quantity
from astropy.io.votable.tree import Field
from astropy.table import Table
from .query import DALResults, DALQuery, DALService, Record
from .adhoc import DatalinkResultsMixin, DatalinkRecordMixin
__all__ = ["search", "SCSService", "SCSQuery", "SCSResults", "SCSRecord"]
def search(url, pos, radius=1.0, verbosity=2, **keywords):
"""
submit a simple Cone Search query that requests objects or observations
whose positions fall within some distance from a search position.
Parameters
----------
url : str
the base URL of the query service.
pos : astropy.coordinates.SkyCoord
a SkyCoord instance defining the position of the center of the
circular search region.
converted if it's a iterable containing scalars, assuming icrs degrees.
radius : `~astropy.units.Quantity` or float
a Quantity instance defining the radius of the circular search
region, in degrees.
converted if it is another unit.
verbosity : int
an integer value that indicates the volume of columns
to return in the result table. 0 means the minimum
set of columsn, and 3 means as many columns as are available.
**keywords :
additional case insensitive parameters can be given via arbitrary
case insensitive keyword arguments. Where there is overlap
with the parameters set by the other arguments to
this function, these keywords will override.
Returns
-------
SCSResults
a container holding a table of matching catalog records
Raises
------
DALServiceError
for errors connecting to or communicating with the service.
DALQueryError
if the service responds with an error,
including a query syntax error.
See Also
--------
SCSResults
pyvo.dal.DALServiceError
pyvo.dal.DALQueryError
"""
return SCSService(url).search(pos=pos, radius=radius, verbosity=verbosity, **keywords)
[docs]class SCSService(DALService):
"""
a representation of a Cone Search service
"""
def __init__(self, baseurl, session=None):
"""
instantiate a Cone Search service
Parameters
----------
baseurl : str
the base URL for submitting search queries to the service.
session : object
optional session to use for network requests
"""
super().__init__(baseurl, session=session)
def _get_metadata(self):
"""
download the metadata resource
"""
if not hasattr(self, '_metadata'):
query = self.create_query(pos=(0, 0), radius=0)
metadata = query.execute_votable()
setattr(self, '_metadata', metadata)
@property
def description(self):
"""
the service description.
"""
self._get_metadata()
try:
return getattr(self, '_metadata').description
except AttributeError:
return None
@property
def columns(self):
"""
the available columns on this service
"""
self._get_metadata()
fields = filter(
lambda field_or_param: isinstance(field_or_param, Field),
self._metadata.iter_fields_and_params()
)
try:
return [
TableParam.from_field(field) for field in fields]
except AttributeError:
return []
[docs] def search(self, pos, radius=1.0, verbosity=2, **keywords):
"""
submit a simple Cone Search query that requests objects or observations
whose positions fall within some distance from a search position.
Parameters
----------
pos : astropy.coordinates.SkyCoord
a SkyCoord instance defining the position of the center of the
circular search region.
converted if it's a iterable containing scalars,
assuming icrs degrees.
radius : `~astropy.units.Quantity` or float
a Quantity instance defining the radius of the circular search
region, in degrees.
converted if it is another unit.
verbosity : int
an integer value that indicates the volume of columns
to return in the result table. 0 means the minimum
set of columns, 3 means as many columns as are available.
**keywords :
additional case insensitive parameters can be given via arbitrary
case insensitive keyword arguments. Where there is overlap
with the parameters set by the other arguments to
this function, these keywords will override.
Returns
-------
SCSResults
a container holding a table of matching catalog records
Raises
------
DALServiceError
for errors connecting to or communicating with the service
DALQueryError
if the service responds with an error,
including a query syntax error.
See Also
--------
SCSResults
pyvo.dal.DALServiceError
pyvo.dal.DALQueryError
"""
return self.create_query(pos=pos, radius=radius, verbosity=verbosity, **keywords).execute()
[docs] def create_query(self, pos=None, radius=None, verbosity=None, **keywords):
"""
create a query object that constraints can be added to and then
executed. The input arguments will initialize the query with the
given values.
Parameters
----------
pos : astropy.coordinates.SkyCoord
a SkyCoord instance defining the position of the center of the
circular search region.
converted if it's a iterable containing scalars,
assuming icrs degrees.
radius : `~astropy.units.Quantity` or float
a Quantity instance defining the radius of the circular search
region, in degrees.
converted if it is another unit.
verbosity : int
an integer value that indicates the volume of columns
to return in the result table. 0 means the minimum
set of columns, 3 means as many columns as are available.
**keywords :
additional case insensitive parameters can be given via arbitrary
case insensitive keyword arguments. Where there is overlap
with the parameters set by the other arguments to
this function, these keywords will override.
Returns
-------
SCSQuery
the query instance
See Also
--------
SCSQuery
"""
return SCSQuery(self.baseurl, pos=pos, radius=radius, verbosity=verbosity,
session=self._session, **keywords)
[docs] def describe(self):
print(self.description)
print()
rows = [(
col.name,
col.description,
col.unit,
col.ucd,
col.utype,
col.datatype.arraysize,
col.datatype.content,
) for col in self.columns]
names = (
'name',
'description',
'unit',
'ucd',
'utype',
'arraysize',
'datatype',
)
table = Table(rows=rows, names=names)
table.pprint(
max_lines=-1, max_width=-1, show_unit=False, show_dtype=False)
[docs]class SCSQuery(DALQuery):
"""
a class for preparing an query to a Cone Search service. Query constraints
are added via its service type-specific methods. The various execute()
functions will submit the query and return the results.
The base URL for the query, which controls where the query will be sent
when one of the execute functions is called, is typically set at
construction time; however, it can be updated later via the
:py:attr:`~pyvo.dal.DALQuery.baseurl` to send a configured
query to another service.
In addition to the search constraint attributes described below, search
parameters can be set generically by name via dict semantics.
The typical function for submitting the query is ``execute()``; however,
alternate execute functions provide the response in different forms,
allowing the caller to take greater control of the result processing.
"""
def __init__(
self, baseurl, pos=None, radius=None, verbosity=None, session=None, **keywords):
"""
initialize the query object with a baseurl and the given parameters
Parameters
----------
pos : astropy.coordinates.SkyCoord
a SkyCoord instance defining the position of the center of the
circular search region.
converted if it's a iterable containing scalars,
assuming icrs degrees.
radius : `~astropy.units.Quantity` or float
a Quantity instance defining the radius of the circular search
region, in degrees.
converted if it is another unit.
verbosity : int
an integer value that indicates the volume of columns
to return in the result table. 0 means the minimum
set of columns, 3 means as many columns as are
available.
session : object
optional session to use for network requests
"""
super().__init__(baseurl, session=session)
if pos is not None:
self.pos = pos
if radius is not None:
self.radius = radius
if verbosity is not None:
self.verbosity = verbosity
self.update({key.upper(): value for key, value in keywords.items()})
@property
def pos(self):
"""
the position of the center of the circular search region as a
`~astropy.coordinates.SkyCoord` instance.
"""
return getattr(self, "_pos", None)
@pos.setter
def pos(self, pos):
setattr(self, "_pos", pos)
if not isinstance(pos, SkyCoord):
try:
ra, dec = pos
except (TypeError, ValueError):
raise ValueError(
'Pos must be a sequence with exactly two values, '
'expressing ra and dec in icrs degrees'
)
# assume degrees
pos = SkyCoord(ra=ra, dec=dec, unit="deg", frame="icrs")
self["RA"] = pos.icrs.ra.deg
self["DEC"] = pos.icrs.dec.deg
@pos.deleter
def pos(self):
delattr(self, "_pos")
del self["RA"]
del self["DEC"]
@property
def radius(self):
"""
the radius of the circular region around pos as a
`~astropy.units.Quantity` instance.
"""
return getattr(self, "_radius", None)
@radius.setter
def radius(self, radius):
setattr(self, "_radius", radius)
if not isinstance(radius, Quantity):
valerr = ValueError("Radius must be exactly one value")
try:
# assume degrees
radius = radius * Unit("deg")
except ValueError:
raise valerr
try:
if len(radius):
raise valerr
except TypeError:
pass # len 1
self["SR"] = radius.to(Unit("deg")).value
@radius.deleter
def radius(self):
delattr(self, "_radius")
del self["SR"]
@property
def verbosity(self):
"""
an integer value that indicates the volume of columns
to return in the result table. 0 means the minimum
set of columsn, 3 means as many columns as are available.
"""
return getattr(self, "_verbosity", None)
@verbosity.setter
def verbosity(self, verbosity):
setattr(self, "_verbosity", verbosity)
self["VERB"] = verbosity
@verbosity.deleter
def verbosity(self):
delattr(self, "_verbosity")
del self["VERB"]
[docs] def execute(self):
"""
submit the query and return the results as a SCSResults instance
Raises
------
DALServiceError
for errors connecting to or communicating with the service
DALQueryError
for errors either in the input query syntax or
other user errors detected by the service
DALFormatError
for errors parsing the VOTable response
"""
return SCSResults(self.execute_votable(), url=self.queryurl, session=self._session)
[docs]class SCSResults(DatalinkResultsMixin, DALResults):
"""
The list of matching catalog records resulting from a catalog (SCS) query.
Each record contains a set of metadata that describes a source or
observation within the requested circular region (i.e. a "cone"). The
number of records in the results is available by passing it to the Python built-in
``len()`` function.
This class supports iterable semantics; thus,
individual records (in the form of
:py:class:`~pyvo.dal.scs.SCSRecord` instances) are typically
accessed by iterating over an ``SCSResults`` instance.
Alternatively, records can be accessed randomly via
:py:meth:`getrecord` or through a Python Database API (v2)
Cursor (via :py:meth:`~pyvo.dal.DALResults.cursor`).
Column-based data access is possible via the
:py:meth:`~pyvo.dal.DALResults.getcolumn` method.
``SCSResults`` is essentially a wrapper around an Astropy
:py:mod:`~astropy.io.votable`
:py:class:`~astropy.io.votable.tree.TableElement` instance where the
columns contain the various metadata describing the images.
One can access that VOTable directly via the
:py:attr:`~pyvo.dal.DALResults.votable` attribute. Thus,
when one retrieves a whole column via
:py:meth:`~pyvo.dal.DALResults.getcolumn`, the result is
a Numpy array. Alternatively, one can manipulate the results
as an Astropy :py:class:`~astropy.table.table.Table` via the
following conversion:
``table = results.votable.to_table()``
``SCSResults`` supports the array item operator ``[...]`` in a
read-only context. When the argument is numerical, the result
is an
:py:class:`~pyvo.dal.scs.SCSRecord` instance, representing the
record at the position given by the numerical index. If the
argument is a string, it is interpreted as the name of a column,
and the data from the column matching that name is returned as
a Numpy array.
"""
def _findresultsresource(self, votable):
if len(votable.resources) < 1:
return None
return votable.resources[0]
def _findstatus(self, votable):
# this is specialized according to the Conesearch standard
# look first in the preferred location: just below the root VOTABLE
info = self._findstatusinfo(votable.infos)
if info:
return (info.name, info.value)
# look next in the result resource
res = self._findresultsresource(votable)
if res:
# look for RESOURCE/INFO
info = self._findstatusinfo(res.infos)
if info:
return (info.name, info.value)
# if not there, check for a PARAM
info = self._findstatusinfo(res.params)
if info:
return (info.name, info.value)
# last resort: VOTABLE/DEFINITIONS/PARAM
# NOT SUPPORTED BY astropy; parser has been configured to
# raise W22 as exception instead.
# assume it's okay
return ("OK", "Successful Response")
def _findstatusinfo(self, infos):
# this can be overridden to specialize for a particular DAL protocol
for info in infos:
if info.name == "Error":
return info
[docs] def getrecord(self, index):
"""
return a representation of a conesearch result record that follows
dictionary semantics. The keys of the dictionary are those returned by
this instance's fieldnames attribute. The returned record has the
following additional properties: id, ra, dec
Parameters
----------
index : int
the integer index of the desired record where 0 returns the first
record
Returns
-------
SCSRecord
a dictionary-like wrapper containing the result record metadata.
Raises
------
IndexError
if index is negative or equal or larger than the number of rows in
the result table.
See Also
--------
Record
"""
return SCSRecord(self, index, session=self._session)
[docs]class SCSRecord(DatalinkRecordMixin, Record):
"""
a dictionary-like container for data in a record from the results of an
Cone Search (SCS) query, describing a matching source or observation.
The commonly accessed metadata which are stadardized by the SCS
protocol are available as attributes. All metadata, particularly
non-standard metadata, are acessible via the ``get(`` *key* ``)``
function (or the [*key*] operator) where *key* is table column name.
"""
@property
def pos(self):
"""
the position of the object or observation described by this record.
"""
return SkyCoord(
ra=self.getbyucd("POS_EQ_RA_MAIN"),
dec=self.getbyucd("POS_EQ_DEC_MAIN"),
unit="deg", frame="icrs")
@property
def id(self):
"""
return the identifying name of the object or observation described by
this record.
"""
return self.getbyucd("ID_MAIN")