Data Access (pyvo.dal)

This subpackage provides access to the various data services in the VO.

Getting started

Service objects are created with the service url and provide service-specific metadata.

>>> import pyvo as vo
>>> service = vo.dal.SIAService("http://dc.zah.uni-heidelberg.de/lswscans/res/positions/siap/siap.xml")
>>> print(service.description)
Scans of plates kept at Landessternwarte Heidelberg-Königstuhl. They
were obtained at location, at the German-Spanish Astronomical Center
(Calar Alto Observatory), Spain, and at La Silla, Chile. The plates
cover a time span between 1880 and 1999.

Specifically, HDAP is essentially complete for the plates taken with
the Bruce telescope, the Walz reflector, and Wolf's Doppelastrograph
at both the original location in Heidelberg and its later home on
Königstuhl.

They provide a search method with varying standard parameters for submitting queries.

>>> resultset = service.search(pos=pos, size=size)

which returns a resultset.

Individual services may define additional, custom parameters. You can pass these to the search method as (case-insensitive) keyword arguments.

Call the method describe to print human-readable service metadata. You most likely want to use this in a notebook session or similar before actually querying the service.

See Services for a explanation of the different interfaces.

Astrometric parameters

Most services expose the astrometric parameters pos and size for which PyVO accept SkyCoord or Quantity objects as well as any other sequence containing right ascension and declination in degrees, which are converted to the standard coordinate frame (in the VO, that usually is ICRS) in the standard units (always degrees in the VO) before they are submitted to the service.

Also, SkyCoord can be used to lookup names of astronomical objects you are searching for.

>>> import pyvo as vo
>>> from astropy.coordinates import SkyCoord
>>> from astropy.units import Quantity
>>>
>>> pos = SkyCoord.from_name('NGC 4993')
>>> size = Quantity(0.5, unit="deg")

See Astronomical Coordinate Systems (astropy.coordinates) and Units and Quantities (astropy.units) for details.

The Quantity object is also suitable for any other astrometric parameter, such as waveband ranges.

Some services also accept Time as time parameter.

>>> from astropy.time import Time
>>> time = Time(('2015-01-01T00:00:00', '2018-01-01T00:00:00'),
...             format='isot', scale='utc')

See Time and Dates (astropy.time) for explanation.

Verbosity

Several VO protocols have the notion of “verbosity”, where 1 means “minimal set of columns”, 2 means “columns most users can work with” and 3 ”everything including exotic items”. Query functions accept these values in the verbosity parameter. The exact semantics are service-specific.

Capabilities

VO services should offer some standard ”support” interfaces specified in VOSI. In pyVO, the information obtained from these endpoints can be obtained from some service attributes.

Capabilities describe specific pieces of functionality (such as “this is a spectral search”) and further metadata (such as ”this service will never return more than 10000 rows”).

This information is contained in the data structure CapabilitiesFile available through the pyvo.dal.vosi.CapabilityMixin.capabilities attribute.

Exceptions

See the pyvo.dal.exceptions module.

Services

There are five types of services with different purposes but a mostly similar interface available.

Table Access Protocol

This protocol defines a service protocol for accessing general table data, including astronomical catalogs as well as general database tables. Access is provided for both database and table metadata as well as for actual table data. This protocol supports the query language Astronomical Data Query Language (ADQL) within an integrated interface. It also includes support for both synchronous and asynchronous queries. Special support is provided for spatially indexed queries using the spatial extensions in ADQL. A multi-position query capability permits queries against an arbitrarily large list of astronomical targets, providing a simple spatial cross-matching capability. More sophisticated distributed cross-matching capabilities are possible by orchestrating a distributed query across multiple TAP services.

—Table Access Protocol

Consider the following example for using TAP and ADQL, retrieving 5 objects from the GAIA DR3 database, showing their id, position and mean G-band magnitude between 19 - 20:

>>> import pyvo as vo
>>> tap_service = vo.dal.TAPService("http://dc.g-vo.org/tap")
>>> ex_query = """
...     SELECT TOP 5
...     source_id, ra, dec, phot_g_mean_mag
...     FROM gaia.dr3lite
...     WHERE phot_g_mean_mag BETWEEN 19 AND 20
...     ORDER BY phot_g_mean_mag
...     """
>>> result = tap_service.search(ex_query)
>>> print(result)
<DALResultsTable length=5>
    source_id              ra                dec         phot_g_mean_mag
                        deg                deg               mag
    int64             float64            float64           float32
------------------- ------------------ ------------------ ---------------
2162809607452221440 315.96596187101636 45.945474015208106            19.0
2000273643933171456  337.1829026565382   50.7218533537033            19.0
2171530448339798784  323.9151025188806  51.27690705826792            19.0
2171810342771336704 323.25913736080776  51.94305655940998            19.0
2180349528028140800  310.5233961869657   50.3486391034819            19.0

To explore more query examples, you can try either the description attribute for some services. For other services like this one, try the examples attribute.

>>> print(tap_service.examples[0]['QUERY'])
SELECT TOP 50 l.id, l.pmra as lpmra, l.pmde as lpmde,
g.source_id, g.pmra as gpmra, g.pmdec as gpmde
FROM
lspm.main as l
JOIN gaia.dr3lite AS g
ON (DISTANCE(g.ra, g.dec, l.raj2000, l.dej2000)<0.01) -- rough pre-selection
WHERE
DISTANCE(
    ivo_epoch_prop_pos(
    g.ra, g.dec, g.parallax,
    g.pmra, g.pmdec, g.radial_velocity,
    2016, 2000),
    POINT(l.raj2000, l.dej2000)
)<0.0002                            -- fine selection with PMs

Furthermore, one can find the names of the tables using:

>>> print([tab_name for tab_name in tap_service.tables.keys()])  
['ivoa.obs_radio', 'ivoa.obscore', 'tap_schema.columns', 'tap_schema.tables',..., 'taptest.main', 'veronqsos.data', 'vlastripe82.stripe82']

And also the names of the columns from a known table, for instance the first three columns:

>>> result.table.columns[:3]    
<TableColumns names=('source_id','ra','dec')>

If you know a TAP service’s access URL, you can directly pass it to TAPService to obtain a service object. Sometimes, such URLs are published in papers or passed around through other channels. Most commonly, you will discover them in the VO registry (cf. pyvo.registry).

To perform a query using ADQL, the search() method is used. TAPService instances have several methods to inspect the metadata of the service - in particular, what tables with what columns are available - discussed below.

To get an idea of how to write queries in ADQL, have a look at GAVO’s ADQL course; it is basically a standardised subset of SQL with some extensions to make it work better for astronomy.

Synchronous vs. asynchronous query

In synchronous (“sync”) mode, the client keeps a connection for the entire runtime of the query, and query processing generally starts when the request is submitted. This is convenient but becomes brittle as queries have runtimes of the order of minutes, when you may encounter query timeouts. Also, many data providers impose rather strict limits on the runtime allotted to sync queries.

In asynchronous (“async”) mode, on the other hand, the client just submits a query and receives a URL that let us inspect the execution status (and retrieve its result) later. This means that no connection needs to be held, which makes this mode a lot more robust of long-running queries. It also supports queuing queries, which allows service operators to be a lot more generous with resource limits.

To specify the query mode, you can use either run_sync() for synchronous query or run_async() for asynchronous query.

>>> job = tap_service.submit_job(ex_query)

To learn more details from the asynchronous query, let’s look at the submit_job() method. This submits an asynchronous query without starting it, it creates a new object AsyncTAPJob.

>>> job.url
'http://dc.zah.uni-heidelberg.de/__system__/tap/run/async/...'

The job URL mentioned before is available in the url attribute. Clicking on the URL leads you to the query itself, where you can check the status(phase) of the query and decide to run, modify or delete the job. You can also do it via various attributes:

>>> job.phase
'PENDING'

A newly created job is in the PENDING state. While it is pending, it can be configured, for instance, overriding the server’s default time limit (after which the query will be canceled):

>>> job.executionduration = 700
>>> job.executionduration
700

When you are ready, you can start the job:

>>> job.run()
<pyvo.dal.tap.AsyncTAPJob object at 0x...>

This will put the job into the QUEUED state. Depending on how busy the server is, it will immediately go to the EXECUTING status:

>>> job.phase   
'EXECUTING'

The job will eventually end up in one of the phases:

  • COMPLETED - if all went to plan,

  • ERROR - if the query failed for some reason;

    look at the error attribute of the job to find out details,

  • ABORTED - if you manually killed the query using the abort()

    method or the server killed your query, presumably because it hit the time limit.

After the job ends up in COMPLETED, you can retrieve the result:

>>> job.phase  
'COMPLETED'
>>> job.fetch_result()  
(result table as shown before)

Eventually, it is friendly to clean up the job rather than relying on the server to clean it up once job.destruction (a datetime that you can change if you need to) is reached.

>>> job.delete()

For more attributes please read the description for the job object AsyncTAPJob.

With run_async() you basically submit an asynchronous query and return its result. It is like running submit_job() first and then run the query manually.

Query limit

As a sanity precaution, most services have some default limit of how many rows they will return before overflowing:

>>> print(tap_service.maxrec)
20000

To retrieve more rows than that (often conservative) default limit, you must override maxrec in the call to search. A warning can be expected if you reach the maxrec limit:

>>> tap_results = tap_service.search("SELECT * FROM ivoa.obscore", maxrec=100000)  
DALOverflowWarning: Partial result set. Potential causes MAXREC, async storage space, etc.

Services will not let you raise maxrec beyond the hard match limit:

>>> print(tap_service.hardlimit)
16000000

A list of the tables and the columns within them is available in the TAPService’s tables attribute by using it as an iterator or calling it’s describe() method for a human-readable summary.

Uploads

Some TAP services allow you to upload your own tables to make them accessible in queries.

For this the various query methods have a uploads keyword, which accepts a dictionary of table name and content.

The mechanism behind this parameter is smart enough to distinct between various types of content, either a str pointing to a local file or a file-like object, a Table or DALResults for an inline upload, or a url str pointing to a remote resource.

The uploaded tables will be available as TAP_UPLOAD.name.

Note

The supported upload methods are available under upload_methods().

Table Manipulation

Note

This is a prototype implementation and the interface might not be stable. More details about the feature at: CADC Table Manipulation (cadc-tb-upload)

Some services allow users to create, modify and delete tables. Typically, these functionality is only available to authenticated (and authorized) users.

>>> auth_session = vo.auth.AuthSession()
>>> # authenticate. For ex: auth_session.credentials.set_client_certificate('<cert_file>')
>>> tap_service = vo.dal.TAPService("https://ws-cadc.canfar.net/youcat", auth_session)
>>>
>>> table_definition = '''
... <vosi:table xmlns:vosi="http://www.ivoa.net/xml/VOSITables/v1.0" xmlns:vod="http://www.ivoa.net/xml/VODataService/v1.1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" type="output">
...     <name>my_table</name>
...     <description>This is my very own table</description>
...     <column>
...         <name>article</name>
...         <description>some article</description>
...         <dataType xsi:type="vod:VOTableType" arraysize="30*">char</dataType>
...     </column>
...     <column>
...         <name>count</name>
...         <description>how many</description>
...         <dataType xsi:type="vod:VOTableType">long</dataType>
...     </column>
... </vosi:table> '''
>>> tap_service.create_table(name='test_schema.test_table', definition=StringIO(table_definition))

Table content can be loaded from a file or from memory. Supported data formats: tab-separated values (tsv), comma-separated values (cvs) or VOTable (VOTable):

>>> tap_service.load_table(name='test_schema.test_table',
...                        source=StringIO('article,count\narticle1,10\narticle2,20\n'), format='csv')

Users can also create indexes on single columns: .. doctest-skip:

>>> tap_service.create_index(table_name='test_schema.test_table', column_name='article', unique=True)

Finally, tables and their content can be removed:

>>> tap_service.remove_table(name='test_schema.test_table')

For further information about the service’s parameters, see TAPService.

Simple Image Access

The Simple Image Access (SIA) protocol provides capabilities for the discovery, description, access, and retrieval of multi-dimensional image datasets, including 2-D images as well as datacubes of three or more dimensions. SIA data discovery is based on the ObsCore Data Model, which primarily describes data products by the physical axes (spatial, spectral, time, and polarization). Image datasets with dimension greater than 2 are often referred to as datacubes, cube or image cube datasets and may be considered examples of hypercube or n-cube data. PyVO supports both versions of SIA.

—Simple Image Access

Basic queries are done with the pos and size parameters described in Astrometric parameters, with size being the rectangular region around pos.

>>> pos = SkyCoord.from_name('Eta Carina')
>>> size = Quantity(0.5, unit="deg")
>>> sia_service = vo.dal.SIAService("http://dc.zah.uni-heidelberg.de/hppunion/q/im/siap.xml")
>>> sia_results = sia_service.search(pos=pos, size=size)

The dataset format, ‘all’ by default, can be specified:

>>> sia_results = sia_service.search(pos=pos, size=size, format='graphics')

This would return all graphical image formats (png, jpeg, gif) available. Other possible values are image/* mimetypes, or metadata, which returns no image at all but instead a declaration of the additional parameters supported by the given service.

The intersect argument (defaulting to OVERLAPS) lets a program specify the desired relationship between the region of interest and the coverage of the images (case-insensitively):

>>> sia_results = sia_service.search(pos=pos, size=size, intersect='covers')
Available values:

COVERS

select images that completely cover the search region

ENCLOSED

select images that are complete enclosed by the region

OVERLAPS

select any image that overlaps with the search region

CENTER

select images whose center is within the search region

This service exposes the verbosity parameter

For further information about the service’s parameters, see SIAService.

Simple Spectrum Access

The Simple Spectral Access (SSA) Protocol (SSAP) defines a uniform interface to remotely discover and access one dimensional spectra.

—Simple Spectral Access Protocol

Access to (one-dimensional) spectra resembles image access, with some subtile differences:

The size parameter is called diameter here, and hence the search region is always circular with pos as center:

>>> ssa_service = vo.dal.SSAService("https://irsa.ipac.caltech.edu/SSA")
>>> ssa_results = ssa_service.search(pos=pos, diameter=size)

SSA queries can be further constrained by the band and time parameters.

>>> ssa_results = ssa_service.search(
...     pos=pos, diameter=size,
...     time=Time((53000, 54000), format='mjd'), band=Quantity((1e-13, 1e-12), unit="m"))

For further information about the service’s parameters, see SSAService.

Simple Line Access

The Simple Line Access Protocol (SLAP) is an IVOA data access protocol which defines a protocol for retrieving spectral lines coming from various Spectral Line Data Collections through a uniform interface within the VO framework.

—Simple Line Access Protocol

This service let you query for spectral lines in a certain wavelength range. The unit of the values is meters, but any unit may be specified using Quantity. For further information about the service’s parameters, see SLAService.

Jobs

Some services, most notably TAP ones, allow asynchronous operation (i.e., you submit a job, receive a URL where to check for updates, and then can go away) using a VO standard called UWS.

These have a submit_job method, which has the same parameters as their search but start a server-side job instead of waiting for the result to return.

This is particularly useful for longer-running queries or when you want to run several queries in parallel from one script.

Note

It is good practice to test the query with a maxrec constraint first.

When you invoke submit_job you will get a job object.

>>> async_srv = vo.dal.TAPService("http://dc.g-vo.org/tap")
>>> job = async_srv.submit_job("SELECT * FROM ivoa.obscore")

Note

Currently, only pyvo.dal.tap.TAPService supports server-side jobs.

This job is not yet running yet. To start it invoke run

>>> job.run()

Get the current job phase:

>>> print(job.phase)
EXECUTING

Maximum run time in seconds is available and can be changed with execution_duration

>>> print(job.execution_duration)
7200.0
>>> job.execution_duration = 3600

Obtaining the job url, which is needed to reconstruct the job at a later point:

>>> job_url = job.url
>>> job = vo.dal.tap.AsyncTAPJob(job_url)

Besides run there are also several other job control methods:

Note

Usually the service deletes the job after a certain time, but it is a good practice to delete it manually when done.

The destruction time can be obtained and changed with destruction

Also, pyvo.dal.AsyncTAPJob works as a context manager which takes care of this automatically:

>>> with async_srv.submit_job("SELECT * FROM ivoa.obscore") as job1:
...     job1.run()  
>>> print('job1 deleted!')
job1 deleted!

Check for errors in the job execution:

>>> job.raise_if_error()

If the execution was successful, the resultset can be obtained using fetch_result()

The result url is available under result_uri

Resultsets and Records

Resultsets contain primarily tabular data and might also provide binary datasets and/or access to additional data services.

To obtain the names of the columns in a service response, write:

>>> tap_service = vo.dal.TAPService("http://dc.g-vo.org/tap")
>>> resultset = tap_service.search("SELECT TOP 10 * FROM ivoa.obscore")
>>> print(resultset.fieldnames)
('dataproduct_type', 'dataproduct_subtype', 'calib_level',
'obs_collection', 'obs_id', 'obs_title', 'obs_publisher_did',
'obs_creator_did', 'access_url', 'access_format', 'access_estsize',
'target_name', 'target_class', 's_ra', 's_dec', 's_fov', 's_region',
's_resolution', 't_min', 't_max', 't_exptime', 't_resolution', 'em_min',
'em_max', 'em_res_power', 'o_ucd', 'pol_states', 'facility_name',
'instrument_name', 's_xel1', 's_xel2', 't_xel', 'em_xel', 'pol_xel',
's_pixel_scale', 'em_ucd', 'preview', 'source_table')

Rich metadata equivalent to what is found in VOTables (including unit, ucd, utype, and xtype) is available through resultset’s getdesc() method:

>>> print(resultset.getdesc('s_fov').ucd)
phys.angSize;instr.fov

Note

Two convenience functions let you retrieve columns of a specific physics (by UCD) or with a particular legacy data model annotation (by utype), like this:

>>> fieldname = resultset.fieldname_with_ucd('phys.angSize;instr.fov')
>>> fieldname = resultset.fieldname_with_utype('obscore:access.reference')

Iterating over a resultset gives the rows in the result:

>>> for row in resultset:
...     print(row['s_fov'])
0.05027778
0.05027778
0.05027778
0.05027778
0.05027778
0.05027778
0.06527778
0.06527778
0.06527778
0.06527778

The total number of rows in the answer is available as its len():

>>> print(len(resultset))
10

If the row contains datasets, they are exposed by several retrieval methods:

>>> url = row.getdataurl()
>>> fileobj = row.getdataset()
>>> obj = row.getdataobj()

Returning the access url, the file-like object or the appropriate python object to further work on.

As with general numpy arrays, accessing individual columns via names gives an array of all of their values:

>>> column = resultset['obs_id']

whereas integers retrieve rows:

>>> row = resultset[0]

and both combined gives a single value:

>>> value = resultset['obs_id', 0]

Row objects may expose certain key columns as properties. See the corresponding API spec listed below for details.

Convenience methods are available to transform the results into astropy.table.Table or astropy.table.QTable (values as quantities):

>>> astropy_table = resultset.to_table()
>>> astropy_qtable = resultset.to_qtable()

Multiple datasets

PyVO supports multiple datasets exposed on record level through the datalink. To get an iterator yielding specific datasets, call pyvo.dal.adhoc.DatalinkResults.bysemantics() with the identifier identifying the dataset you want it to return.

>>> preview = next(row.getdatalink().bysemantics('#preview')).getdataset()

Note

Since the creation of datalink objects requires a network roundtrip, it is recommended to call getdatalink only once.

Of course one can also build a datalink object from its url.

>>> from pyvo.dal.adhoc import DatalinkResults
>>> # In this example you know the URL from somewhere
>>> url = 'https://ws.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/caom2ops/datalink?ID=ivo%3A%2F%2Fcadc.nrc.ca%2FHSTHLA%3Fhst_12477_28_acs_wfc_f606w_01%2Fhst_12477_28_acs_wfc_f606w_01_drz'
>>> datalink = DatalinkResults.from_result_url(url)

Server-side processing

Some services support the server-side processing of record datasets. This includes spatial cutouts for 2d-images, reducing of spectra to a certain waveband range, and many more depending on the service.

SODA

SODA is a service with predefined parameters, available on row-level through pyvo.dal.adhoc.SodaRecordMixin.processed() which exposes a set of parameters which are dependent on the type of service.

  • circle – a sequence (degrees) or astropy.units.Quantity of longitude, latitude and radius

  • range – a sequence (degrees) or astropy.units.Quantity of two longitude values and two latitude values describing a rectangle.

  • polygon – multiple pairs of longitude and latitude points

  • band – a sequence of two values (meters) or astropy.units.Quantity with two bandwidth values. The right sort order will be ensured if converting from frequency to wavelength.

Interoperabillity over SAMP

Tables and datasets can be send to other astronomical applications, providing they have support for SAMP (Simple Application Messaging Protocol).

You can either broadcast whole tables by calling broadcast_samp on the resultset or a single product (image, spectrum) by calling this method on the SIA or SSA record.

Note

Don’t forget to start the application and make sure there is a running SAMP Hub.

Underlying data structures

PyVO also allows access to underlying data structures.

The astropy data classes astropy.table.Table and astropy.table.QTable are accessible with the method pyvo.dal.DALResults.to_table() and pyvo.dal.DALResults.to_qtable(), following astropy naming conventions.

If you want to work with the XML data structures astropy.io.votable.tree.VOTableFile or astropy.io.votable.tree.TableElement, they are accessible by the attributes pyvo.dal.DALResults.resultstable and pyvo.dal.DALResults.votable, respectively.

Reference/API

pyvo.dal Package

Functions

imagesearch(url, pos, *[, size, format, ...])

submit a simple SIA query that requests images overlapping a given region

spectrumsearch(baseurl[, pos, diameter, ...])

submit a simple SSA query that requests spectra overlapping a given region

linesearch(baseurl, wavelength, **keywords)

submit a simple SLA query that requests spectral lines within a wavelength range

conesearch(url, pos[, radius, verbosity])

submit a simple Cone Search query that requests objects or observations whose positions fall within some distance from a search position.

tablesearch(url, query, *[, language, ...])

submit a Table Access query that returns rows matching the criteria given.

imagesearch2(url[, pos, band, time, pol, ...])

submit a simple SIA query to a SIA2 compatible service

Classes

DALService(baseurl, *[, session, ...])

an abstract base class representing a DAL service located a particular endpoint.

SIAService(baseurl, *[, ...])

a representation of an SIA service

SIA2Service(baseurl, *[, ...])

a representation of an SIA2 service

SSAService(baseurl, *[, ...])

a representation of an SSA service

SLAService(baseurl, *[, ...])

a representation of an spectral line catalog (SLA) service

SCSService(baseurl, *[, ...])

a representation of a Cone Search service

TAPService(baseurl, *[, ...])

a representation of a Table Access Protocol service

DALQuery(baseurl, *[, session])

a class for preparing a query to a particular service.

SIAQuery(baseurl[, pos, size, format, ...])

a class for preparing an query to an SIA service.

SIA2Query(url[, pos, band, time, pol, ...])

a class very similar to SIAQuery class but used to interact with SIA2 services.

SSAQuery(baseurl[, pos, diameter, band, ...])

a class for preparing an query to an SSA service.

SLAQuery(baseurl[, wavelength, request, session])

a class for preparing an query to an SLA service.

SCSQuery(baseurl[, pos, radius, verbosity, ...])

a class for preparing an query to a Cone Search service.

TAPQuery(baseurl, query, *[, mode, ...])

a class for preparing an query to an TAP service.

DALResults(votable, *[, url, session])

Results from a DAL query.

SIAResults(votable, *[, url, session])

The list of matching images resulting from an image (SIA) query.

SIA2Results(votable, *[, url, session])

The list of matching images resulting from an image (SIA2) query.

SSAResults(votable, *[, url, session])

The list of matching images resulting from a spectrum (SSA) query.

SLAResults(votable, *[, url, session])

The list of matching spectral lines resulting from a spectal line catalog (SLA) query.

SCSResults(votable, *[, url, session])

The list of matching catalog records resulting from a catalog (SCS) query.

TAPResults(votable, *[, url, session])

The list of matching images resulting from an image (SIA) query.

Record(results, index, *[, session])

one record from a DAL query result.

ObsCoreRecord(results, index, *[, session])

a dictionary-like container for data in a record from the results of an image (SIA2) search, describing an available image in ObsCore format.

SIARecord(results, index, *[, session])

a dictionary-like container for data in a record from the results of an image (SIA) search, describing an available image.

SSARecord(results, index, *[, session])

a dictionary-like container for data in a record from the results of an SSA query, describing an available spectrum.

SLARecord(results, index, *[, session])

a dictionary-like container for data in a record from the results of an spectral line (SLA) query, describing a spectral line transition.

SCSRecord(results, index, *[, session])

a dictionary-like container for data in a record from the results of an Cone Search (SCS) query, describing a matching source or observation.

AsyncTAPJob(url, *[, session])

This class represents a UWS TAP Job.

DALAccessError([reason, url])

a base class for failures while accessing a DAL service

DALProtocolError([reason, cause, url])

a base exception indicating that a DAL service responded with an error.

DALFormatError([cause, url, reason])

an exception indicating that a DAL response contains fatal format errors.

DALServiceError([reason, code, cause, url])

an exception indicating a failure communicating with a DAL service.

DALQueryError([reason, label, url])

an exception indicating an error by a working DAL service while processing a query.

DALOverflowWarning

Class Inheritance Diagram

Inheritance diagram of pyvo.dal.query.DALService, pyvo.dal.sia.SIAService, pyvo.dal.sia2.SIA2Service, pyvo.dal.ssa.SSAService, pyvo.dal.sla.SLAService, pyvo.dal.scs.SCSService, pyvo.dal.tap.TAPService, pyvo.dal.query.DALQuery, pyvo.dal.sia.SIAQuery, pyvo.dal.sia2.SIA2Query, pyvo.dal.ssa.SSAQuery, pyvo.dal.sla.SLAQuery, pyvo.dal.scs.SCSQuery, pyvo.dal.tap.TAPQuery, pyvo.dal.query.DALResults, pyvo.dal.sia.SIAResults, pyvo.dal.sia2.SIA2Results, pyvo.dal.ssa.SSAResults, pyvo.dal.sla.SLAResults, pyvo.dal.scs.SCSResults, pyvo.dal.tap.TAPResults, pyvo.dal.query.Record, pyvo.dal.sia2.ObsCoreRecord, pyvo.dal.sia.SIARecord, pyvo.dal.ssa.SSARecord, pyvo.dal.sla.SLARecord, pyvo.dal.scs.SCSRecord, pyvo.dal.tap.AsyncTAPJob, pyvo.dal.exceptions.DALAccessError, pyvo.dal.exceptions.DALProtocolError, pyvo.dal.exceptions.DALFormatError, pyvo.dal.exceptions.DALServiceError, pyvo.dal.exceptions.DALQueryError, pyvo.dal.exceptions.DALOverflowWarning

pyvo.dal.adhoc Module

Datalink classes and mixins

Classes

AdhocServiceResultsMixin(votable, *[, url, ...])

Mixin for adhoc:service functionallity for results classes.

DatalinkResultsMixin(votable, *[, url, session])

Mixin for datalink functionallity for results classes.

DatalinkRecordMixin()

Mixin for record classes, providing functionallity for datalink.

DatalinkService(baseurl[, session])

a representation of a Datalink service

DatalinkQuery(baseurl, *[, id, ...])

A class for preparing a query to a Datalink service.

DatalinkResults(votable, *[, url, session])

The list of matching records resulting from an datalink query.

DatalinkRecord(results, index, *[, session])

a dictionary-like container for data in a record from the results of an datalink query,

SodaRecordMixin()

Mixin for soda functionality for record classes.

SodaQuery(baseurl, *[, circle, range, ...])

a class for preparing a query to a SODA Service.

Class Inheritance Diagram

Inheritance diagram of pyvo.dal.adhoc.AdhocServiceResultsMixin, pyvo.dal.adhoc.DatalinkResultsMixin, pyvo.dal.adhoc.DatalinkRecordMixin, pyvo.dal.adhoc.DatalinkService, pyvo.dal.adhoc.DatalinkQuery, pyvo.dal.adhoc.DatalinkResults, pyvo.dal.adhoc.DatalinkRecord, pyvo.dal.adhoc.SodaRecordMixin, pyvo.dal.adhoc.SodaQuery