Butler¶

class lsst.daf.butler.Butler(config=None, collection=None, run=None)¶

Bases: object

Main entry point for the data access system.

Parameters:	config : `Config` Configuration. collection : `str`, optional Collection to use for all input lookups, overriding config[“collection”] if provided. run : `str`, `Run`, optional Collection associated with the `Run` to use for outputs, overriding config[“run”]. If a `Run` associated with the given Collection does not exist, it will be created. If “collection” is None, this collection will be used for input lookups as well; if not, it must have the same value as “run”.
Raises:	ValueError Raised if neither “collection” nor “run” are provided by argument or config, or if both are provided and are inconsistent.
Attributes:	config : `str`, `ButlerConfig` or `Config`, optional (filename to) configuration. If this is not a `ButlerConfig`, defaults will be read. If a `str`, may be the path to a directory containing a “butler.yaml” file. datastore : `Datastore` Datastore to use for storage. registry : `Registry` Registry to use for lookups.

Methods Summary

`datasetExists`(datasetType, dataId)	Return True if the Dataset is actually present in the Datastore.
`get`(datasetRefOrType[, dataId, parameters])	Retrieve a stored dataset.
`getDirect`(ref[, parameters])	Retrieve a stored dataset.
`getUri`(datasetType, dataId[, predict])	Return the URI to the Dataset.
`makeRepo`(root[, config, standalone, …])	Create an empty data repository by adding a butler.yaml config to a repository root directory.
`put`(obj, datasetRefOrType[, dataId, producer])	Store and register a dataset.
`transaction`()	Context manager supporting `Butler` transactions.

Methods Documentation

datasetExists(datasetType, dataId)¶

Return True if the Dataset is actually present in the Datastore.

Parameters:	datasetType : `DatasetType` instance or `str` The `DatasetType`. dataId : `dict` A `dict` of `DataUnit` link name, value pairs that label the `DatasetRef` within a Collection.
Raises:	LookupError Raised if the Dataset is not even present in the Registry.

get(datasetRefOrType, dataId=None, parameters=None)¶

Retrieve a stored dataset.

Parameters:

datasetRefOrType : DatasetRef, DatasetType instance or str: When DatasetRef the dataId should be None. Otherwise the DatasetType or name thereof.
dataId : dict: A dict of DataUnit link name, value pairs that label the DatasetRef within a Collection. When None a DatasetRef should be supplied as the second argument.
parameters : dict: Additional StorageClass-defined options to control reading, typically used to efficiently read only a subset of the dataset.

Returns:

obj : object: The dataset.

getDirect(ref, parameters=None)¶

Retrieve a stored dataset.

Unlike Butler.get, this method allows datasets outside the Butler’s collection to be read as long as the DatasetRef that identifies them can be obtained separately.

Parameters:	ref : `DatasetRef` Reference to an already stored dataset. parameters : `dict` Additional StorageClass-defined options to control reading, typically used to efficiently read only a subset of the dataset.
Returns:	obj : `object` The dataset.

getUri(datasetType, dataId, predict=False)¶

Return the URI to the Dataset.

Parameters:	datasetType : `DatasetType` instance or `str` The `DatasetType`. dataId : `dict` A `dict` of `DataUnit` link name, value pairs that label the `DatasetRef` within a Collection. predict : `bool` If `True`, allow URIs to be returned of datasets that have not been written.
Returns:	uri : `str` URI string pointing to the Dataset within the datastore. If the Dataset does not exist in the datastore, and if `predict` is `True`, the URI will be a prediction and will include a URI fragment “#predicted”. If the datastore does not have entities that relate well to the concept of a URI the returned URI string will be descriptive. The returned URI is not guaranteed to be obtainable.
Raises:	FileNotFoundError A URI has been requested for a dataset that does not exist and guessing is not allowed.

static makeRepo(root, config=None, standalone=False, createRegistry=True)¶

Create an empty data repository by adding a butler.yaml config to a repository root directory.

Parameters:	root : `str` Filesystem path to the root of the new repository. Will be created if it does not exist. config : `Config`, optional Configuration to write to the repository, after setting any root-dependent Registry or Datastore config options. If `None`, default configuration will be used. standalone : `bool` If True, write all expanded defaults, not just customized or repository-specific settings. This (mostly) decouples the repository from the default configuration, insulating it from changes to the defaults (which may be good or bad, depending on the nature of the changes). Future additions to the defaults will still be picked up when initializing `Butlers` to repos created with `standalone=True`. createRegistry : `bool` If `True` create a new Registry. Note that when ``standalone=False`` (the default), the configuration search path (see `ConfigSubset.defaultSearchPaths`) that was used to construct the repository should also be used to construct any Butlers to it to avoid configuration inconsistencies.
Returns:	config : `Config` The updated `Config` instance written to the repo.
Raises:	ValueError Raised if a ButlerConfig or ConfigSubset is passed instead of a regular Config (as these subclasses would make it impossible to support `standalone=False`). os.error Raised if the directory does not exist, exists but is not a directory, or cannot be created.

put(obj, datasetRefOrType, dataId=None, producer=None)¶

Store and register a dataset.

Parameters:	obj : `object` The dataset. datasetRefOrType : `DatasetRef`, `DatasetType` instance or `str` When `DatasetRef` the `dataId` should be `None`. Otherwise the `DatasetType` or name thereof. dataId : `dict`, optional An identifier with `DataUnit` names and values. When `None` a `DatasetRef` should be supplied as the second argument. producer : `Quantum`, optional The producer.
Returns:	ref : `DatasetRef` A reference to the stored dataset, updated with the correct id if given.
Raises:	TypeError Raised if the butler was not constructed with a Run, and is hence read-only.

transaction()¶

Context manager supporting Butler transactions.

Transactions can be nested.

Navigation

Butler¶