Source code for pyvo.dal.scs

# 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]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