Source code for astroquery.xmatch.core

# Licensed under a 3-clause BSD style license - see LICENSE.rst

import six
from astropy.io import ascii
import astropy.units as u
from astropy.table import Table

from . import conf
from ..query import BaseQuery
from ..utils import url_helpers, prepend_docstr_nosections, async_to_sync

try:
    from regions import CircleSkyRegion
except ImportError:
    print('Could not import regions, which is required for some of the '
          'functionalities of this module.')


[docs]@async_to_sync class XMatchClass(BaseQuery): URL = conf.url TIMEOUT = conf.timeout
[docs] def query(self, cat1, cat2, max_distance, colRA1=None, colDec1=None, colRA2=None, colDec2=None, area='allsky', cache=True, get_query_payload=False): """ Query the `CDS cross-match service <http://cdsxmatch.u-strasbg.fr/xmatch>`_ by finding matches between two (potentially big) catalogues. Parameters ---------- cat1 : str, file or `~astropy.table.Table` Identifier of the first table. It can either be a URL, the payload of a local file being uploaded, a CDS table identifier (either *simbad* for a view of SIMBAD data / to point out a given VizieR table) or a an AstroPy table. If the table is uploaded or accessed through a URL, it must be in VOTable or CSV format with the positions in J2000 equatorial frame and as decimal degrees numbers. cat2 : str or file Identifier of the second table. Follows the same rules as *cat1*. max_distance : `~astropy.units.Quantity` Maximum distance to look for counterparts. Maximum allowed value is 180 arcsec. colRA1 : str Name of the column holding the right ascension. Only required if ``cat1`` is an uploaded table or a pointer to a URL. colDec1 : str Name of the column holding the declination. Only required if ``cat1`` is an uploaded table or a pointer to a URL. colRA2 : str Name of the column holding the right ascension. Only required if ``cat2`` is an uploaded table or a pointer to a URL. colDec2 : str Name of the column holding the declination. Only required if ``cat2`` is an uploaded table or a pointer to a URL. area : ``regions.CircleSkyRegion`` or 'allsky' str Restrict the area taken into account when performing the xmatch Default value is 'allsky' (no restriction). If a ``regions.CircleSkyRegion`` object is given, only sources in this region will be considered. Returns ------- table : `~astropy.table.Table` Query results table """ response = self.query_async(cat1, cat2, max_distance, colRA1, colDec1, colRA2, colDec2, area=area, cache=cache, get_query_payload=get_query_payload) if get_query_payload: return response return self._parse_text(response.text)
[docs] @prepend_docstr_nosections("\n" + query.__doc__) def query_async(self, cat1, cat2, max_distance, colRA1=None, colDec1=None, colRA2=None, colDec2=None, area='allsky', cache=True, get_query_payload=False): """ Returns ------- response : `~requests.Response` The HTTP response returned from the service. """ if max_distance > 180 * u.arcsec: raise ValueError( 'max_distance argument must not be greater than 180') payload = { 'request': 'xmatch', 'distMaxArcsec': max_distance.to(u.arcsec).value, 'RESPONSEFORMAT': 'csv', } kwargs = {} self._prepare_sending_table(1, payload, kwargs, cat1, colRA1, colDec1) self._prepare_sending_table(2, payload, kwargs, cat2, colRA2, colDec2) self._prepare_area(payload, area) if get_query_payload: return payload, kwargs response = self._request(method='POST', url=self.URL, data=payload, timeout=self.TIMEOUT, cache=cache, **kwargs) response.raise_for_status() return response
def _prepare_sending_table(self, i, payload, kwargs, cat, colRA, colDec): '''Check if table is a string, a `astropy.table.Table`, etc. and set query parameters accordingly. ''' catstr = 'cat{0}'.format(i) if isinstance(cat, six.string_types): payload[catstr] = cat elif isinstance(cat, Table): # write the Table's content into a new, temporary CSV-file # so that it can be pointed to via the `files` option # file will be closed when garbage-collected fp = six.StringIO() cat.write(fp, format='ascii.csv') fp.seek(0) kwargs['files'] = {catstr: ('cat1.csv', fp.read())} else: # assume it's a file-like object, support duck-typing kwargs['files'] = {catstr: ('cat1.csv', cat.read())} if not self.is_table_available(cat): if ((colRA is None) or (colDec is None)): raise ValueError('Specify the name of the RA/Dec columns in' + ' the input table.') # if `cat1` is not a VizieR table, # it is assumed it's either a URL or an uploaded table payload['colRA{0}'.format(i)] = colRA payload['colDec{0}'.format(i)] = colDec def _prepare_area(self, payload, area): '''Set the area parameter in the payload''' if area is None or area == 'allsky': payload['area'] = 'allsky' elif isinstance(area, CircleSkyRegion): payload['area'] = 'cone' cone_center = area.center payload['coneRA'] = cone_center.icrs.ra.deg payload['coneDec'] = cone_center.icrs.dec.deg payload['coneRadiusDeg'] = area.radius.to_value(u.deg) else: raise ValueError('Unsupported area {}'.format(str(area)))
[docs] def is_table_available(self, table_id): """Return True if the passed CDS table identifier is one of the available VizieR tables, otherwise False. """ if isinstance(table_id, six.string_types) and (table_id[:7] == 'vizier:'): table_id = table_id[7:] return table_id in self.get_available_tables()
[docs] def get_available_tables(self, cache=True): """Get the list of the VizieR tables which are available in the xMatch service and return them as a list of strings. """ response = self._request( 'GET', url_helpers.urljoin_keep_path(self.URL, 'tables'), {'action': 'getVizieRTableNames', 'RESPONSEFORMAT': 'txt'}, cache=cache, ) content = response.text return content.splitlines()
def _parse_text(self, text): """ Parse a CSV text file that has potentially duplicated header names """ header = text.split("\n")[0] colnames = header.split(",") for cn in colnames: if colnames.count(cn) > 1: ii = 1 while colnames.count(cn) > 0: colnames[colnames.index(cn)] = cn + "_{ii}".format(ii=ii) ii += 1 new_text = ",".join(colnames) + "\n" + "\n".join(text.split("\n")[1:]) result = ascii.read(new_text, format='csv') return result
XMatch = XMatchClass()