BaseReferencesTask¶

class lsst.meas.base.BaseReferencesTask(butler=None, schema=None, **kwargs)¶

Bases: lsst.pipe.base.Task

Base class for forced photometry subtask that fetches reference sources.

Parameters:	schema : `lsst.afw.table.Schema`, optional The schema of the reference catalog. butler : `lsst.daf.persistence.butler.Butler`, optional A butler that will allow the task to load its schema from disk.

Notes

At least one of the schema and butler arguments must be present; if both are, schema takes precedence.

BaseReferencesTask defines the required API for the references task, which consists of:

getSchema(butler)
fetchInPatches(butler, tract, filter, patchList)
fetchInBox(self, butler, tract, filter, bbox, wcs)
the removePatchOverlaps config option

It also provides the subset method, which may be of use to derived classes when reimplementing fetchInBox.

Methods Summary

`emptyMetadata`()	Empty (clear) the metadata for this Task and all sub-Tasks.
`fetchInBox`(dataRef, bbox, wcs)	Return reference sources within a given bounding box.
`fetchInPatches`(dataRef, patchList)	Return reference sources within one or more patches.
`getAllSchemaCatalogs`()	Get schema catalogs for all tasks in the hierarchy, combining the results into a single dict.
`getFullMetadata`()	Get metadata for all tasks.
`getFullName`()	Get the task name as a hierarchical name including parent task names.
`getName`()	Get the name of the task.
`getSchema`(butler)	Return the schema for the reference sources.
`getSchemaCatalogs`()	Get the schemas generated by this task.
`getTaskDict`()	Get a dictionary of all tasks as a shallow copy.
`getWcs`(dataRef)	Return the WCS for reference sources.
`makeField`(doc)	Make a `lsst.pex.config.ConfigurableField` for this task.
`makeSubtask`(name, **keyArgs)	Create a subtask as a new instance as the `name` attribute of this task.
`subset`(sources, bbox, wcs)	Filter a list of sources to only those within the bounding box.
`timer`(name[, logLevel])	Context manager to log performance data for an arbitrary block of code.

Methods Documentation

emptyMetadata()¶: Empty (clear) the metadata for this Task and all sub-Tasks.

fetchInBox(dataRef, bbox, wcs)¶

Return reference sources within a given bounding box.

Reference sources are selected if they overlap a region defined by a pixel-coordinate bounding box and corresponding WCS.

Parameters:	dataRef : `lsst.daf.persistence.ButlerDataRef` Butler data reference. The implied data ID must contain the `tract` key. bbox : `lsst.afw.geom.Box2I` or `lsst.afw.geom.Box2D` Defines the selection region in pixel coordinates. wcs : `lsst.afw.image.SkyWcs` Maps `bbox` to sky coordinates.
Returns:	sources : iterable of `SourceRecord` Reference sources. May be any Python iterable, including a lazy iterator.

Notes

The returned set of sources should be complete and close to minimal.

fetchInPatches(dataRef, patchList)¶

Return reference sources within one or more patches.

Parameters:	dataRef : `lsst.daf.persistence.ButlerDataRef` Butler data reference. The implied data ID must contain the `tract` key. patchList : `list` of `lsst.skymap.PatchInfo` Patches for which to fetch reference sources.
Returns:	sources : iterable of `SourceRecord` Reference sources. May be any Python iterable, including a lazy iterator.

Notes

The returned set of sources should be complete and close to minimal.

If config.removePatchOverlaps is True, only sources within each patch’s “inner” bounding box should be returned.

getAllSchemaCatalogs()¶

Get schema catalogs for all tasks in the hierarchy, combining the results into a single dict.

Returns:	schemacatalogs : `dict` Keys are butler dataset type, values are a empty catalog (an instance of the appropriate `lsst.afw.table` Catalog type) for all tasks in the hierarchy, from the top-level task down through all subtasks.

Notes

This method may be called on any task in the hierarchy; it will return the same answer, regardless.

The default implementation should always suffice. If your subtask uses schemas the override Task.getSchemaCatalogs, not this method.

getFullMetadata()¶

Get metadata for all tasks.

Returns:	metadata : `lsst.daf.base.PropertySet` The `PropertySet` keys are the full task name. Values are metadata for the top-level task and all subtasks, sub-subtasks, etc.

Notes

The returned metadata includes timing information (if @timer.timeMethod is used) and any metadata set by the task. The name of each item consists of the full task name with . replaced by :, followed by . and the name of the item, e.g.:

topLevelTaskName:subtaskName:subsubtaskName.itemName

using : in the full task name disambiguates the rare situation that a task has a subtask and a metadata item with the same name.

getFullName()¶

Get the task name as a hierarchical name including parent task names.

Returns:	fullName : `str` The full name consists of the name of the parent task and each subtask separated by periods. For example: The full name of top-level task “top” is simply “top”. The full name of subtask “sub” of top-level task “top” is “top.sub”. The full name of subtask “sub2” of subtask “sub” of top-level task “top” is “top.sub.sub2”.

getName()¶

Get the name of the task.

Returns:	taskName : `str` Name of the task.

See also

Task.getAllSchemaCatalogs

Notes

Warning

Subclasses that use schemas must override this method. The default implementation returns an empty dict.

This method may be called at any time after the Task is constructed, which means that all task schemas should be computed at construction time, not when data is actually processed. This reflects the philosophy that the schema should not depend on the data.

Returning catalogs rather than just schemas allows us to save e.g. slots for SourceCatalog as well.

getTaskDict()¶

Get a dictionary of all tasks as a shallow copy.

Returns:	taskDict : `dict` Dictionary containing full task name: task object for the top-level task and all subtasks, sub-subtasks, etc.

getWcs(dataRef)¶

Return the WCS for reference sources.

Parameters:	dataRef : `lsst.daf.persistence.ButlerDataRef` The data reference from which the WCS will be fetched. This must include the tract in its dataId.

classmethod makeField(doc)¶

Make a lsst.pex.config.ConfigurableField for this task.

Parameters:	doc : `str` Help text for the field.
Returns:	configurableField : `lsst.pex.config.ConfigurableField` A `ConfigurableField` for this task.

Examples

Provides a convenient way to specify this task is a subtask of another task.

Here is an example of use:

class OtherTaskConfig(lsst.pex.config.Config):
    aSubtask = ATaskClass.makeField("brief description of task")

makeSubtask(name, **keyArgs)¶

Create a subtask as a new instance as the name attribute of this task.

Parameters:	name : `str` Brief name of the subtask. keyArgs Extra keyword arguments used to construct the task. The following arguments are automatically provided and cannot be overridden: “config”. “parentTask”.

Notes

The subtask must be defined by Task.config.name, an instance of ConfigurableField or RegistryField.

subset(sources, bbox, wcs)¶

Filter a list of sources to only those within the bounding box.

Parameters:	sources : iterable of `SourceRecord` Reference sources. May be any Python iterable, including a lazy iterator. bbox : `lsst.afw.geom.Box2I` or `lsst.afw.geom.Box2D` Defines the selection region. wcs : `lsst.afw.image.SkyWcs` Maps `bbox` to sky coordinates.
Returns:	sources : iterable of `SourceRecord` Filtered sources. May be any Python iterable, including a lazy iterator.

Notes

Instead of filtering sources directly via their positions, we filter based on the positions of parent objects, then include or discard all children based on their parent’s status. This is necessary to support replacement with noise in measurement, which requires all child sources have their parent present.

This is not a part of the required BaseReferencesTask interface; it’s a convenience function used in implementing fetchInBox that may be of use to subclasses.

timer(name, logLevel=10000)¶

Context manager to log performance data for an arbitrary block of code.

Parameters:	name : `str` Name of code being timed; data will be logged using item name: `Start` and `End`. logLevel A `lsst.log` level constant.

Navigation

BaseReferencesTask¶