DeferredDatasetHandle

class lsst.daf.butler.DeferredDatasetHandle(butler: LimitedButler, ref: DatasetRef, parameters: dict | None, storageClass: str | StorageClass | None = None)

Bases: object

Proxy class that provides deferred loading of datasets from a butler.

Attributes Summary

butler	The butler that will be used to fetch the dataset (LimitedButler).
dataId	The full data ID associated with the dataset (DataCoordinate).
parameters	Optional parameters that may be used to specify a subset of the dataset to be loaded (dict or None).
ref	Reference to the dataset (DatasetRef).
storageClass	Optional storage class override that can be applied on get().

Methods Summary

get(*[, component, parameters, storageClass])

Retrieve the dataset pointed to by this handle.

Attributes Documentation

butler: LimitedButler = <dataclasses._MISSING_TYPE object>

The butler that will be used to fetch the dataset (LimitedButler).

dataId

The full data ID associated with the dataset (DataCoordinate).

Guaranteed to contain records.

parameters: dict | None = <dataclasses._MISSING_TYPE object>

Optional parameters that may be used to specify a subset of the dataset to be loaded (dict or None).

ref: DatasetRef = <dataclasses._MISSING_TYPE object>

Reference to the dataset (DatasetRef).

storageClass: str | StorageClass | None = None

Optional storage class override that can be applied on get().

Methods Documentation

get(*, component: str | None = None, parameters: dict | None = None, storageClass: str | StorageClass | None = None) → Any

Retrieve the dataset pointed to by this handle.

This handle may be used multiple times, possibly with different parameters.

Parameters

componentstr or None

If the deferred object is a component dataset type, this parameter may specify the name of the component to use in the get operation.

parametersdict or None

The parameters argument will be passed to the butler get method. It defaults to None. If the value is not None, this dict will be merged with the parameters dict used to construct the DeferredDatasetHandle class.

storageClassStorageClass or str, optional

The storage class to be used to override the Python type returned by this method. By default the returned type matches the dataset type definition for this dataset or the storage class specified when this object was created. Specifying a read StorageClass can force a different type to be returned. This type must be compatible with the original type.

Returns

returnObject

The dataset pointed to by this handle.