| 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. | 
| DataCoordinate | An immutable data ID dictionary that guarantees that its key-value pairs identify all required dimensions in a DimensionGraph. | 
| DatasetComponent(name, storageClass, component) | Component of a dataset and associated information. | 
| DatasetRef | 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. | 
| DbAuth([path, envVar, authList]) | Retrieves authentication information for database connections. | 
| DbAuthError | A problem has occurred retrieving database authentication information. | 
| DbAuthPermissionsError | Credentials file has incorrect permissions. | 
| DeferredDatasetHandle(butler, …) | This is a class to support deferred loading of a dataset from a butler. | 
| Dimension(name, *, uniqueKeys, **kwds) | A named data-organization concept that can be used as a key in a data ID. | 
| DimensionConfig([other, validate, …]) | Configuration that defines a DimensionUniverse. | 
| DimensionElement(name, *, …) | A named data-organization concept that defines a label and/or metadata in the dimensions system. | 
| DimensionGraph | An immutable, dependency-complete collection of dimensions. | 
| DimensionPacker(fixed, dimensions) | An abstract base class for bidirectional mappings between a DataCoordinateand a packed integer ID. | 
| DimensionRecord(*args) | Base class for the Python representation of database records for a DimensionElement. | 
| DimensionUniverse | A special DimensionGraphthat constructs and manages a complete set of compatible dimensions. | 
| ExpandedDataCoordinate | A data ID that has been expanded to include all relevant metadata. | 
| FieldSpec(name, dtype, length, nbytes, …) | A struct-like class used to define a column in a logical Registry table. | 
| FileDataset(path, ref, *, formatter, str, …) | A struct that represents a dataset exported to a file. | 
| 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 | 
| ForeignKeySpec(table, source, …], target, …) | A struct-like class used to define a foreign key constraint in a logical Registry table. | 
| Formatter(fileDescriptor) | 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(*[, taskName, taskClass, dataId, …]) | A discrete unit of work that may depend on one or more datasets and produces one or more datasets. | 
| Registry(registryConfig[, schemaConfig, …]) | Registry interface. | 
| RepoExport(registry, datastore, backend, *, …) | Public interface for exporting a subset of a data repository. | 
| RepoExportBackend | An abstract interface for data repository export implementations. | 
| RepoImportBackend | An abstract interface for data repository import implementations. | 
| RepoTransferFormatConfig([other, validate, …]) | The section of butler configuration that associates repo import/export backends with file formats. | 
| Schema([spec]) | The SQL schema for a Butler Registry. | 
| SchemaConfig([other, validate, …]) |  | 
| SkyPixDimension(name, pixelization) | A special Dimensionsubclass for hierarchical pixelizations of the sky. | 
| StorageClass([name, pytype, components, …]) | Class describing how a label maps to a particular Python type. | 
| StorageClassConfig([other, validate, …]) |  | 
| StorageClassFactory([config]) | Factory for StorageClassinstances. | 
| StoredDatastoreItemInfo | Internal information associated with a stored dataset in a Datastore. | 
| StoredFileInfo(formatter, path, …) | Datastore-private metadata associated with a file stored in a Datastore. | 
| TableSpec(fields, unique, …]], …) | A struct-like class used to define a logical Registry table (which may also be implemented in the database as a view). | 
| ValidationError | Some sort of validation error has occurred. | 
| YamlRepoExportBackend(stream) | A repository export implementation that saves to a YAML file. | 
| YamlRepoImportBackend(stream) | A repository import implementation that reads from a YAML file. |