JsonFormatter

class lsst.daf.butler.formatters.json.JsonFormatter(fileDescriptor: FileDescriptor, dataId: DataCoordinate, writeParameters: Optional[Dict[str, Any]] = None, writeRecipes: Optional[Dict[str, Any]] = None)

Bases: FileFormatter

Formatter implementation for JSON files.

Attributes Summary

dataId	Return Data ID associated with this formatter (DataCoordinate).
extension	Default file extension to use for writing files.
fileDescriptor	File descriptor associated with this formatter (FileDescriptor).
supportedExtensions	Set of all extensions supported by this formatter.
supportedWriteParameters	Parameters understood by this formatter that can be used to control how a dataset is serialized.
unsupportedParameters	This formatter does not support any parameters (frozenset)
writeParameters	Parameters to use when writing out datasets.
writeRecipes	Detailed write Recipes indexed by recipe name.

Methods Summary

can_read_bytes()	Indicate if this formatter can format from bytes.
fromBytes(serializedDataset[, component])	Reads serialized data into a Dataset or its component.
makeUpdatedLocation(location)	Return a new Location updated with this formatter's extension.
name()	Return the fully qualified name of the formatter.
predictPath()	Return the path that would be returned by write.
read([component])	Read data from a file.
segregateParameters([parameters])	Segregate the supplied parameters.
toBytes(inMemoryDataset)	Serialize the Dataset to bytes based on formatter.
validateExtension(location)	Check the extension of the provided location for compatibility.
validateWriteRecipes(recipes)	Validate supplied recipes for this formatter.
write(inMemoryDataset)	Write a Python object to a file.

Attributes Documentation

dataId

Return Data ID associated with this formatter (DataCoordinate).

extension: Optional[str] = '.json'

Default file extension to use for writing files. None means that no modifications will be made to the supplied file extension. (str)

fileDescriptor

File descriptor associated with this formatter (FileDescriptor).

Read-only property.

supportedExtensions: ClassVar[AbstractSet[str]] = frozenset({})

Set of all extensions supported by this formatter.

Only expected to be populated by Formatters that write files. Any extension assigned to the extension property will be automatically included in the list of supported extensions.

supportedWriteParameters: ClassVar[Optional[AbstractSet[str]]] = None

Parameters understood by this formatter that can be used to control how a dataset is serialized. None indicates that no parameters are supported.

unsupportedParameters: ClassVar[Optional[AbstractSet[str]]] = None

This formatter does not support any parameters (frozenset)

writeParameters

Parameters to use when writing out datasets.

writeRecipes

Detailed write Recipes indexed by recipe name.

Methods Documentation

classmethod can_read_bytes() → bool

Indicate if this formatter can format from bytes.

Returns:

canbool

True if the fromBytes method is implemented.

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

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.

Raises:

NotImplementedError

Formatter does not support reading from bytes.

makeUpdatedLocation(location: Location) → Location

Return a new Location updated with this formatter’s extension.

Parameters:

locationLocation

The location to update.

Returns:

updatedLocation

A new Location with a new file extension applied.

Raises:

NotImplementedError

Raised if there is no extension attribute associated with this formatter.

Notes

This method is available to all Formatters but might not be implemented by all formatters. It requires that a formatter set an extension attribute containing the file extension used when writing files. If extension is None the supplied file will not be updated. Not all formatters write files so this is not defined in the base class.

classmethod name() → str

Return 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.

Does not write any data file.

Uses the FileDescriptor associated with the instance.

Returns:

pathstr

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

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

Read data from a file.

Parameters:

fileDescriptorFileDescriptor

Identifies the file to read, type to read it into and parameters to be used for reading.

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

Raises:

ValueError

Component requested but this file does not seem to be a concrete composite.

NotImplementedError

Formatter does not implement a method to read from files.

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

Segregate the supplied parameters.

This splits the 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

Object to serialize.

Returns:

serializedDatasetbytes

Bytes representing the serialized dataset.

Raises:

NotImplementedError

Formatter does not support reading from bytes.

classmethod validateExtension(location: Location) → None

Check the extension of the provided location for compatibility.

Parameters:

locationLocation

Location from which to extract a file extension.

Raises:

NotImplementedError

Raised if file extensions are a concept not understood by this formatter.

ValueError

Raised if the formatter does not understand this extension.

Notes

This method is available to all Formatters but might not be implemented by all formatters. It requires that a formatter set an extension attribute containing the file extension used when writing files. If extension is None only the set of supported extensions will be examined.

classmethod validateWriteRecipes(recipes: Optional[Mapping[str, Any]]) → Optional[Mapping[str, Any]]

Validate supplied recipes for this formatter.

The recipes are supplemented with default values where appropriate.

Parameters:

recipesdict

Recipes to validate.

Returns:

validateddict

Validated recipes.

Raises:

RuntimeError

Raised if validation fails. The default implementation raises if any recipes are given.

write(inMemoryDataset: Any) → None

Write a Python object to a file.

Parameters:

inMemoryDatasetobject

The Python object to store.

Returns:

pathstr

The path where the primary file is stored within the datastore.