Formatter

class lsst.daf.butler.Formatter(fileDescriptor: lsst.daf.butler.core.fileDescriptor.FileDescriptor)

Bases: object

Interface for reading and writing Datasets with a particular StorageClass.

Parameters

fileDescriptorFileDescriptor, optional

Identifies the file to read or write, and the associated storage classes and parameter information. Its value can be None if the caller will never call Formatter.read or Formatter.write.

Attributes Summary

fileDescriptor	FileDescriptor associated with this formatter (FileDescriptor, read-only)
unsupportedParameters	Set of parameters not understood by this Formatter.

Methods Summary

fromBytes(serializedDataset[, component])	Reads serialized data into a Dataset or its component.
name()	Returns the fully qualified name of the formatter.
predictPath()	Return the path that would be returned by write, without actually writing.
predictPathFromLocation(location)	Return the path that would be returned by write, without actually writing.
read([component])	Read a Dataset.
segregateParameters([parameters])	Segregate the supplied parameters into those understood by the formatter and those not understood by the formatter.
toBytes(inMemoryDataset)	Serialize the Dataset to bytes based on formatter.
write(inMemoryDataset)	Write a Dataset.

Attributes Documentation

fileDescriptor

FileDescriptor associated with this formatter (FileDescriptor, read-only)

unsupportedParameters = frozenset({})

Set of parameters not understood by this Formatter. An empty set means all parameters are supported. None indicates that no parameters are supported (frozenset).

Methods Documentation

fromBytes(serializedDataset: bytes, component: Optional[str] = None) → object

Reads serialized data into a Dataset or its component.

Parameters

serializedDatasetbytes

Bytes object to unserialize.

componentstr, optional

Component to read from the Dataset. Only used if the StorageClass for reading differed from the StorageClass used to write the file.

Returns

inMemoryDatasetobject

The requested data as a Python object. The type of object is controlled by the specific formatter.

classmethod name() → str

Returns the fully qualified name of the formatter.

Returns

namestr

Fully-qualified name of formatter class.

predictPath() → str

Return the path that would be returned by write, without actually writing.

Uses the FileDescriptor associated with the instance.

Returns

pathstr

Path within datastore that would be associated with the location stored in this Formatter.

abstract classmethod predictPathFromLocation(location: lsst.daf.butler.core.location.Location) → str

Return the path that would be returned by write, without actually writing.

Parameters

locationLocation

Location of file for which path prediction is required.

Returns

pathstr

Path within datastore that would be associated with this location.

abstract read(component: Optional[str] = None) → object

Read a Dataset.

Parameters

componentstr, optional

Component to read from the file. Only used if the StorageClass for reading differed from the StorageClass used to write the file.

Returns

inMemoryDatasetobject

The requested Dataset.

segregateParameters(parameters: Optional[Dict[str, Any]] = None) → Tuple[Dict, Dict]

Segregate the supplied parameters into those understood by the formatter and those not understood by the formatter.

Any unsupported parameters are assumed to be usable by associated assemblers.

Parameters

parametersdict, optional

Parameters with values that have been supplied by the caller and which might be relevant for the formatter. If None parameters will be read from the registered FileDescriptor.

Returns

supporteddict

Those parameters supported by this formatter.

unsupporteddict

Those parameters not supported by this formatter.

toBytes(inMemoryDataset: Any) → bytes

Serialize the Dataset to bytes based on formatter.

Parameters

inMemoryDatasetobject

The Python object to serialize.

Returns

serializedDatasetbytes

Bytes representing the serialized dataset.

abstract write(inMemoryDataset: Any) → str

Write a Dataset.

Parameters

inMemoryDatasetobject

The Dataset to store.

Returns

pathstr

The path to where the Dataset was stored within the datastore.