ButlerQuantumContext

class lsst.pipe.base.ButlerQuantumContext(butler: Butler, quantum: Quantum)

Bases: object

A Butler-like class specialized for a single quantum

A ButlerQuantumContext class wraps a standard butler interface and specializes it to the context of a given quantum. What this means in practice is that the only gets and puts that this class allows are DatasetRefs that are contained in the quantum.

In the future this class will also be used to record provenance on what was actually get and put. This is in contrast to what the preflight expects to be get and put by looking at the graph before execution.

Parameters:

butlerlsst.daf.butler.Butler

Butler object from/to which datasets will be get/put

quantumlsst.daf.butler.core.Quantum

Quantum object that describes the datasets which will be get/put by a single execution of this node in the pipeline graph. All input dataset references must be resolved (i.e. satisfy DatasetRef.id is not None) prior to constructing the ButlerQuantumContext.

Notes

Most quanta in any non-trivial graph will not start with resolved dataset references, because they represent processing steps that can only run after some other quanta have produced their inputs. At present, it is the responsibility of lsst.ctrl.mpexec.SingleQuantumExecutor to resolve all datasets prior to constructing ButlerQuantumContext and calling runQuantum, and the fact that this precondition is satisfied by code in a downstream package is considered a problem with the pipe_base/ctrl_mpexec separation of concerns that will be addressed in the future.

Methods Summary

get(dataset)	Fetches data from the butler
put(values, dataset)	Puts data into the butler

Methods Documentation

get(dataset: InputQuantizedConnection | List[DatasetRef] | List[DeferredDatasetRef] | DatasetRef | DeferredDatasetRef) → Any

Fetches data from the butler

Parameters:

dataset

This argument may either be an InputQuantizedConnection which describes all the inputs of a quantum, a list of DatasetRef, or a single DatasetRef. The function will get and return the corresponding datasets from the butler.

Returns:

returnobject

This function returns arbitrary objects fetched from the bulter. The structure these objects are returned in depends on the type of the input argument. If the input dataset argument is a InputQuantizedConnection, then the return type will be a dictionary with keys corresponding to the attributes of the InputQuantizedConnection (which in turn are the attribute identifiers of the connections). If the input argument is of type list of DatasetRef then the return type will be a list of objects. If the input argument is a single DatasetRef then a single object will be returned.

Raises:

ValueError

Raised if a DatasetRef is passed to get that is not defined in the quantum object

put(values: Struct | List[Any] | Any, dataset: OutputQuantizedConnection | List[DatasetRef] | DatasetRef) → None

Puts data into the butler

Parameters:

valuesStruct or list of object or object

The data that should be put with the butler. If the type of the dataset is OutputQuantizedConnection then this argument should be a Struct with corresponding attribute names. Each attribute should then correspond to either a list of object or a single object depending of the type of the corresponding attribute on dataset. I.e. if dataset.calexp is [datasetRef1, datasetRef2] then values.calexp should be [calexp1, calexp2]. Like wise if there is a single ref, then only a single object need be passed. The same restriction applies if dataset is directly a list of DatasetRef or a single DatasetRef.

dataset

This argument may either be an InputQuantizedConnection which describes all the inputs of a quantum, a list of lsst.daf.butler.DatasetRef, or a single lsst.daf.butler.DatasetRef. The function will get and return the corresponding datasets from the butler.

Raises:

ValueError

Raised if a DatasetRef is passed to put that is not defined in the quantum object, or the type of values does not match what is expected from the type of dataset.