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.
"""
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.query.DALServiceError
    pyvo.dal.query.DALQueryError
    """
    return SCSService(url).search(pos, radius, 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.query.DALServiceError pyvo.dal.query.DALQueryError """ return self.create_query(pos, radius, 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, radius, 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.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 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 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. 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. """ 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")