Dimension

class lsst.daf.butler.Dimension(universe, name, config)

Bases: lsst.daf.butler.DimensionElement

A discrete dimension of data used to organize Datasets and associate them with metadata.

Dimension instances represent concepts such as “Instrument”, “Detector”, “Visit” and “SkyMap”, which are usually associated with database tables. A DatasetType is associated with a fixed combination of Dimensions.

Dimension objects are not directly constructable; they can only be obtained from a DimensionGraph.

Attributes Summary

doc	Documentation for this dimension (str).
hasRegion	Whether this dimension is associated with a region on the sky (bool).
name	Name of this dimension (str, read-only).
universe	The graph of all dimensions compatible with self (DimensionGraph).

Methods Summary

dependencies([required, implied])	Return the set of dimensions this dimension depends on.
graph([implied])	Return the minimal DimensionGraph that contains self.
links([expand, implied])	Return the names of fields that uniquely identify this dimension in a data ID dict.

Attributes Documentation

doc

Documentation for this dimension (str).

hasRegion

Whether this dimension is associated with a region on the sky (bool).

name

Name of this dimension (str, read-only).

Also assumed to be the name of any associated table or view.

universe

The graph of all dimensions compatible with self (DimensionGraph).

Methods Documentation

dependencies(required=True, implied=False)

Return the set of dimensions this dimension depends on.

Parameters:

required : bool

If True (default), include required dependencies. Required dependences are always expanded recursively.

implied : bool

If True, return implied dependencies.

Returns:

dependencies : DimensionSet

graph(implied=False)

Return the minimal DimensionGraph that contains self.

Parameters:

implied : bool

If True, include implied as well as required dependencies.

Returns:

graph : DimensionGraph

links(expand=True, implied=False)

Return the names of fields that uniquely identify this dimension in a data ID dict.

Parameters:

expand: `bool`

If True (default) include links associated with required dependencies.

implied: `bool`

If True, expand to include the links of implied dpendencies as well. Ignored if expand is False.

Returns:

links : frozenset of str

Set of field names.