DimensionGroup

class lsst.daf.butler.DimensionGroup(universe: DimensionUniverse, names: Iterable[str] | DimensionGroup = frozenset({}), _conform: bool = True)

Bases: object

An immutable, dependency-complete collection of dimensions.

DimensionGroup behaves in many respects like a set of str dimension names that maintains several special subsets and supersets of related dimension elements. It does not fully implement the collections.abc.Set interface, because it defines a few different iteration orders and does not privilege any one of them by implementing __iter__.

Parameters:

universeDimensionUniverse

Object that manages all known dimensions.

namesiterable of str, optional

An iterable of the names of dimensions that must be included in the group. All (recursive) dependencies of these dimensions will also be included. At most one of dimensions and names must be provided.

_conformbool, optional

If True (default), expand to include dependencies. False should only be used for callers that can guarantee that other arguments are already correctly expanded, and is for internal use only.

Notes

DimensionGroup should be used instead of other collections in most contexts where a collection of dimensions is required and a DimensionUniverse is available. Exceptions include cases where order matters (and is different from the consistent ordering defined by the DimensionUniverse), or complete Set semantics are required.

Attributes Summary

data_coordinate_keys	A set of dimensions ordered like DataCoordinate.mapping.
lookup_order	A tuple of all elements in the order needed to find their records.
spatial	Families represented by the spatial elements in this graph.
temporal	Families represented by the temporal elements in this graph.

Methods Summary

as_group()	Return self.
intersection(*others)	Construct a new group with only dimensions in all of the operands.
isdisjoint(other)	Test whether the intersection of two groups is empty.
issubset(other)	Test whether all dimensions in self are also in other.
issuperset(other)	Test whether all dimensions in other are also in self.
union(*others)	Construct a new group with all dimensions in any of the operands.

Attributes Documentation

data_coordinate_keys

A set of dimensions ordered like DataCoordinate.mapping.

This order is defined as all required dimensions followed by all implied dimensions.

lookup_order

A tuple of all elements in the order needed to find their records.

Unlike the table definition/topological order (which is what DimensionUniverse.sorted gives you), when dimension A implies dimension B, dimension A appears first.

spatial

Families represented by the spatial elements in this graph.

temporal

Families represented by the temporal elements in this graph.

Methods Documentation

as_group() → DimensionGroup

Return self.

This is a backwards-compatibility API that allows both DimensionGraph and DimensionGroup to be coerced to the latter.

intersection(*others: DimensionGroup) → DimensionGroup

Construct a new group with only dimensions in all of the operands.

See also union.

isdisjoint(other: DimensionGroup) → bool

Test whether the intersection of two groups is empty.

Returns True if either operand is the empty.

issubset(other: DimensionGroup) → bool

Test whether all dimensions in self are also in other.

Returns True if self is empty.

issuperset(other: DimensionGroup) → bool

Test whether all dimensions in other are also in self.

Returns True if other is empty.

union(*others: DimensionGroup) → DimensionGroup

Construct a new group with all dimensions in any of the operands.

The elements of the returned group may exceed the naive union of their elements, as some dimension elements are included in groups whenever multiple dimensions are present, and those dependency dimensions could have been provided by different operands.