SnapCombineTask¶

class lsst.pipe.tasks.snapCombine.SnapCombineTask(*args, **kwargs)¶

Bases: lsst.pipe.base.Task

Combine two snaps into a single visit image.

Notes

Debugging: The lsstDebug variables in SnapCombineTask are:

display A dictionary containing debug point names as keys with frame number as value. Valid keys are:

repair0
Display the first snap after repairing.
repair1
Display the second snap after repairing.

Methods Summary

`addSnaps`(snap0, snap1)	Add two snap exposures together, returning a new exposure.
`emptyMetadata`()	Empty (clear) the metadata for this Task and all sub-Tasks.
`fixMetadata`(combinedMetadata, metadata0, …)	Fix the metadata of the combined exposure (in place).
`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.
`getSchemaCatalogs`()	Get the schemas generated by this task.
`getTaskDict`()	Get a dictionary of all tasks as a shallow copy.
`makeField`(doc)	Make a `lsst.pex.config.ConfigurableField` for this task.
`makeInitialPsf`(exposure[, fwhmPix])	Initialise the detection procedure by setting the PSF and WCS.
`makeSubtask`(name, **keyArgs)	Create a subtask as a new instance as the `name` attribute of this task.
`run`(snap0, snap1[, defects])	Combine two snaps.
`timer`(name, logLevel)	Context manager to log performance data for an arbitrary block of code.

Methods Documentation

addSnaps(snap0, snap1)¶

Add two snap exposures together, returning a new exposure.

Parameters:	snap0 : `Unknown` Snap exposure 0. snap1 : `Unknown` Snap exposure 1.
Returns:	combinedExp : `Unknown` Combined exposure.

emptyMetadata() → None¶: Empty (clear) the metadata for this Task and all sub-Tasks.

fixMetadata(combinedMetadata, metadata0, metadata1)¶

Fix the metadata of the combined exposure (in place).

This implementation handles items specified by config.averageKeys and config.sumKeys, which have data type restrictions. To handle other data types (such as sexagesimal positions and ISO dates) you must supplement this method with your own code.

Parameters:	combinedMetadata : `lsst.daf.base.PropertySet` Metadata of combined exposure; on input this is a deep copy of metadata0 (a PropertySet). metadata0 : `lsst.daf.base.PropertySet` Metadata of snap0 (a PropertySet). metadata1 : `lsst.daf.base.PropertySet` Metadata of snap1 (a PropertySet).

Notes

The inputs are presently PropertySets due to ticket #2542. However, in some sense they are just PropertyLists that are missing some methods. In particular: comments and order are preserved if you alter an existing value with set(key, value).

getAllSchemaCatalogs() → Dict[str, Any]¶

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() → lsst.pipe.base._task_metadata.TaskMetadata¶

Get metadata for all tasks.

Returns:	metadata : `TaskMetadata` The 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() → str¶

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() → str¶

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() → Dict[str, weakref]¶

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.

classmethod makeField(doc: str) → lsst.pex.config.configurableField.ConfigurableField¶

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")

makeInitialPsf(exposure, fwhmPix=None)¶

Initialise the detection procedure by setting the PSF and WCS.

exposure : lsst.afw.image.Exposure: Exposure to process.

Returns:	psf : `Unknown` PSF, WCS AssertionError Raised if any of the following occur: - No exposure provided. - No wcs in exposure.

makeSubtask(name: str, **keyArgs) → None¶

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.

run(snap0, snap1, defects=None)¶

Combine two snaps.

Parameters:	snap0 : `Unknown` Snapshot exposure 0. snap1 : `Unknown` Snapshot exposure 1. defects : `list` or `None`, optional Defect list (for repair task).
Returns:	result : `lsst.pipe.base.Struct` Results as a struct with attributes: `exposure` Snap-combined exposure. `sources` Detected sources, or `None` if detection not performed.

timer(name: str, logLevel: int = 10) → Iterator[None]¶

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 `logging` level constant.

Navigation

SnapCombineTask¶