# 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.
"""
import numbers
from . import query
from .query import DALQueryError
__all__ = [ "search", "SCSService", "SCSQuery", "SCSResults", "SCSRecord" ]
[docs]def search(url, pos, radius=1.0, verbosity=2):
"""
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 : 2-element tuple of floats
a 2-element tuple containing the ICRS right ascension
and declination defining the position of the center
of the circular search region, in decimal degrees
radius : float
the radius of the circular search region, in decimal
degrees
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.
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.query.DALServiceError
pyvo.dal.query.DALQueryError
"""
service = SCSService(url)
return service.search(pos, radius, verbosity)
[docs]class SCSRecord(query.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.
"""
def __init__(self, results, index):
super(SCSRecord, self).__init__(results, index)
self._ucdcols = results._scscols
self._names = results._recnames
@property
def ra(self):
"""
return the right ascension of the object or observation described by
this record.
"""
return self.get(self._names["ra"])
@property
def dec(self):
"""
return the declination of the object or observation described by
this record.
"""
return self.get(self._names["dec"])
@property
def id(self):
"""
return the identifying name of the object or observation described by
this record.
"""
return self.get(self._names["id"])
[docs]class SCSResults(query.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 via the :py:attr:`nrecs`
attribute or 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.
>>> results = pyvo.conesearch(url, pos=[12.24, -13.1], radius=0.1)
>>> for src in results:
... print(("{0}: {1} {2}".format(src.id, src.ra, src.dec)))
Alternatively, records can be accessed randomly via
:py:meth:`getrecord` or through a Python Database API (v2)
Cursor (via :py:meth:`~pyvo.dal.query.DALResults.cursor`).
Column-based data access is possible via the
:py:meth:`~pyvo.dal.query.DALResults.getcolumn` method.
``SCSResults`` is essentially a wrapper around an Astropy
:py:mod:`~astropy.io.votable`
:py:class:`~astropy.io.votable.tree.Table` instance where the
columns contain the various metadata describing the images.
One can access that VOTable directly via the
:py:attr:`~pyvo.dal.query.DALResults.votable` attribute. Thus,
when one retrieves a whole column via
:py:meth:`~pyvo.dal.query.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.
"""
RECORD_CLASS = SCSRecord
def __init__(self, votable, url=None, version="1.0"):
"""
initialize the cursor. This constructor is not typically called
by directly applications; rather an instance is obtained from calling
a SCSQuery's execute().
"""
super(SCSResults, self).__init__(votable, url, "scs", version)
self._scscols = {
"ID_MAIN": self.fieldname_with_ucd("ID_MAIN"),
"POS_EQ_RA_MAIN": self.fieldname_with_ucd("POS_EQ_RA_MAIN"),
"POS_EQ_DEC_MAIN": self.fieldname_with_ucd("POS_EQ_DEC_MAIN")
}
self._recnames = { "id": self._scscols["ID_MAIN"],
"ra": self._scscols["POS_EQ_RA_MAIN"],
"dec": self._scscols["POS_EQ_DEC_MAIN"]
}
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]class SCSQuery(query.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.query.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 class attribute, ``std_parameters``, list the parameters
defined by the SCS standard.
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.
"""
RESULTS_CLASS = SCSResults
std_parameters = [ "RA", "DEC", "SR" ]
def __init__(self, baseurl, version="1.0"):
"""
initialize the query object with a baseurl
"""
super(SCSQuery, self).__init__(baseurl, "scs", version)
@property
def ra(self):
"""
the right ascension part of the position constraint (default: None).
"""
return self.get("RA")
@ra.setter
def ra(self, val):
if val is not None:
if not isinstance(val, numbers.Number):
raise ValueError("ra constraint is not a number")
while val < 0:
val = val + 360.0
while val >= 360.0:
val = val - 360.0
self["RA"] = val
@ra.deleter
def ra(self):
del self["RA"]
@property
def dec(self):
"""
the declination part of the position constraint (default: None).
"""
return self.get("DEC")
@dec.setter
def dec(self, val):
if val is not None:
if not isinstance(val, numbers.Number):
raise ValueError("dec constraint is not a number")
if val < -90.0 or val > 90.0:
raise ValueError("dec constraint out-of-range: " + str(val))
self["DEC"] = val
@dec.deleter
def dec(self):
del self["DEC"]
@property
def pos(self):
"""
the position (POS) constraint as a 2-element tuple denoting RA and dec
in decimal degrees. This defaults to None.
"""
return (self.ra, self.dec)
@pos.setter
def pos(self, pair):
if pair is not None and not isinstance(pair, tuple) and \
not isinstance(pair, list):
raise TypeError("create_query(): pos is not a tuple or list")
if len(pair) < 2:
raise ValueError("create_query(): pos has fewer than 2 elements")
self.ra = pair[0]
self.dec = pair[1]
@pos.deleter
def pos(self, pair):
del self.ra
del self.dec
@property
def radius(self):
"""
the radius of the circular (cone) search region.
"""
return self.get("SR")
@radius.setter
def radius(self, val):
if val is not None:
if not isinstance(val, numbers.Number):
raise ValueError("ra constraint is not a number")
if val <= 0.0 or val > 180.0:
raise ValueError("sr constraint out-of-range: " + val)
self["SR"] = val
@radius.deleter
def radius(self):
del self["SR"]
@property
def sr(self):
"""
a synonym for radius
"""
return self.radius
@sr.setter
def sr(self, val):
self.radius = val
@sr.deleter
def sr(self):
del self.radius
@property
def verbosity(self):
"""
a parameter for controling the volume of columns returned.
The value of 0 means the minimum set of columsn, 3 means as
many columns as are available.
"""
return self.get("VERB")
@verbosity.setter
def verbosity(self, val):
# do a check on val
if not isinstance(val, int):
raise ValueError("verbosity value not an integer: " + val)
self["VERB"] = val
@verbosity.deleter
def verbosity(self):
del self["VERB"]
[docs] def execute_votable(self):
"""
submit the query and return the results as an AstroPy votable instance
Raises
------
DALServiceError
for errors connecting to or communicating with the service
DALFormatError
for errors parsing the VOTable response
DALQueryError
for errors in the input query syntax
"""
try:
from astropy.io.votable.exceptions import W22
except ImportError:
raise RuntimeError("astropy votable not available")
try:
return query._votableparse(self.execute_stream().read)
except query.DALAccessError:
raise
except W22 as e:
raise query.DALFormatError("Unextractable Error encoded in " +
"deprecated DEFINITIONS element")
except Exception as e:
raise query.DALFormatError(e, self.getqueryurl())
[docs]class SCSService(query.DALService):
"""
a representation of a Cone Search service
"""
QUERY_CLASS = SCSQuery
def __init__(self, baseurl, resmeta=None, version="1.0"):
"""
instantiate a Cone Search service
Parameters
----------
baseurl : str
the base URL for submitting search queries to the
service.
resmeta : dict
an optional dictionary of properties about the service
"""
super(SCSService, self).__init__(baseurl, "scs", version, resmeta)
[docs] def search(self, pos, radius=1.0, verbosity=2):
"""
submit a simple Cone Search query that requests objects or observations
whose positions fall within some distance from a search position.
Parameters
----------
pos : 2-element tuple/list of floats
a 2-element tuple or list containing the ICRS right ascension
and declination defining the position of the center
of the circular search region, in decimal degrees
radius : float
the radius of the circular search region, in decimal degrees
verbosity : int
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.
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.query.DALServiceError
pyvo.dal.query.DALQueryError
"""
q = self.create_query(pos, radius, verbosity)
return q.execute()
[docs] def create_query(self, pos=None, radius=None, verbosity=None):
"""
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 : 2-element tuple/list of floats
a 2-element tuple or list containing the ICRS right ascension
and declination defining the position of the center
of the circular search region, in decimal degrees
radius : float
the radius of the circular search region, in decimal degrees
verbosity : int
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.
Returns
-------
SCSQuery
the query instance
See Also
--------
SCSQuery
"""
if pos is not None and not isinstance(pos, tuple) and \
not isinstance(pos, list):
raise TypeError("create_query(): pos is not a tuple or list")
q = self.QUERY_CLASS(self._baseurl)
if pos is not None: q.pos = pos
if radius is not None: q.sr = radius
if verbosity is not None: q.verbosity = verbosity
return q