| AmbiguousDatasetError | Exception raised when a DatasetRefhas no ID and aRegistryoperation requires one. | 
| Butler([config, butler, collection, run, …]) | Main entry point for the data access system. | 
| ButlerConfig([other, searchPaths]) | Contains the configuration for a Butler | 
| ButlerURI(uri[, root, forceAbsolute]) | Convenience wrapper around URI parsers. | 
| ButlerValidationError | There is a problem with the Butler configuration. | 
| CompositeAssembler(storageClass) | Class for providing assembler and disassembler support for composites. | 
| CompositesConfig([other, validate, …]) |  | 
| CompositesMap(config, *, universe) | Determine whether a specific datasetType or StorageClass should be disassembled. | 
| Config([other]) | Implements a datatype that is used by Butlerfor configuration parameters. | 
| ConfigSubset([other, validate, …]) | Config representing a subset of a more general configuration. | 
| ConflictingDefinitionError | Exception raised when trying to insert a database record when a conflicting record already exists. | 
| Constraints(config, *, universe) | Determine whether a DatasetRef,DatasetType, orStorageClassis allowed to be handled. | 
| ConstraintsConfig([other]) | Configuration information for Constraints | 
| ConstraintsValidationError | Exception thrown when a constraints list has mutually exclusive definitions. | 
| DataId([dataId, dimensions, dimension, …]) | A dict-like identifier for data usable across multiple collections and DatasetTypes. | 
| DataIdPacker | An abstract base class for a bidirectional mappings between a DataIdand a packed integer orbytesblob. | 
| DataIdPackerDimensions(given, required) | A helper class that holds the three categories of dimensions associated with DataIdPackerobjects. | 
| DatabaseDict(config, types, key, value[, …]) | An abstract base class for dict-like objects with a specific key type and namedtuple values, backed by a database. | 
| DatasetComponent(name, storageClass, component) | Component of a dataset and associated information. | 
| DatasetOriginInfo | Interface for classes providing collection information for pre-flight. | 
| DatasetOriginInfoDef(defaultInputs, …[, …]) | Default implementation of the DatasetOriginInfo. | 
| DatasetRef(datasetType, dataId[, id, run, …]) | Reference to a Dataset in a Registry. | 
| DatasetType(name, dimensions, storageClass, *) | A named category of Datasets that defines how they are organized, related, and stored. | 
| DatasetTypeNotSupportedError | A DatasetTypeis not handled by this routine. | 
| Datastore(config, registry[, butlerRoot]) | Datastore interface. | 
| DatastoreConfig([other, validate, …]) |  | 
| DatastoreValidationError | There is a problem with the Datastore configuration. | 
| Dimension(universe, name, config) | A discrete dimension of data used to organize Datasets and associate them with metadata. | 
| DimensionConfig([other, validate, …]) |  | 
| DimensionElement(universe, name, hasRegion, …) | Base class for elements in the dimension schema. | 
| DimensionGraph(universe, elements, …) | An automatically-expanded collection of both Dimensions andDimensionJoins. | 
| DimensionJoin(universe, name, config) | A join that relates two or more Dimensions. | 
| DimensionKeyDict([other, universe, keys, …]) | An immutable mapping that uses DimensionElementinstances as keys. | 
| DimensionSet(universe, elements[, expand, …]) | A custom set/dict hybrid class for collections of DimensionElements. | 
| DimensionUniverse() | Specialization for a DimensionGraphthat defines a complete system of dimensions. | 
| Execution([startTime, endTime, host, id]) | Any step in a production. | 
| FileDescriptor(location, storageClass[, …]) | Describes a particular file. | 
| FileTemplate(template) | Format a path template into a fully expanded path. | 
| FileTemplateValidationError | Exception thrown when a file template is not consistent with the associated DatasetType. | 
| FileTemplates(config[, default]) | Collection of FileTemplatetemplates. | 
| FileTemplatesConfig([other]) | Configuration information for FileTemplates | 
| Formatter | Interface for reading and writing Datasets with a particular StorageClass. | 
| FormatterFactory() | Factory for Formatterinstances. | 
| Location(datastoreRootUri, path) | Identifies a location within the Datastore. | 
| LocationFactory(datastoreRoot) | Factory for Locationinstances. | 
| LookupKey([name, dimensions, dataId, universe]) | Representation of key that can be used to lookup information based on dataset type name, storage class name, dimensions. | 
| MappingFactory(refType) | Register the mapping of some key to a python type and retrieve instances. | 
| OrphanedRecordError | Exception raised when trying to remove or modify a database record that is still being used in some other table. | 
| Quantum(task, run, *args, **kwargs) | A discrete unit of work that may depend on one or more datasets and produces one or more datasets. | 
| Registry(registryConfig[, schemaConfig, …]) | Registry interface. | 
| RegistryConfig([other, validate, …]) |  | 
| Run(collection[, environment, pipeline]) | Represent a processing run. | 
| Schema([config, limited]) | The SQL schema for a Butler Registry. | 
| SchemaBuilder(config[, limited]) | Builds a Schema step-by-step. | 
| SchemaConfig([other, validate, …]) |  | 
| StorageClass([name, pytype, components, …]) | Class describing how a label maps to a particular Python type. | 
| StorageClassConfig([other, validate, …]) |  | 
| StorageClassFactory([config]) | Factory for StorageClassinstances. | 
| StoredFileInfo(formatter, path, storageClass) | Information associated with a stored file in a Datastore. | 
| ValidationError | Some sort of validation error has occurred. |