ColumnContainer

class lsst.daf.relation.ColumnContainer

Bases: abc.ABC

A abstract base class and factory for expressions that represent containers of multiple column values.

ColumnContainer inheritance is closed to the types already provided by this package. These concrete types can all be constructed via factory methods on ColumnContainer itself, so the derived types themselves only need to be referenced when writing match expressions that process an expression tree. See Extensibility for rationale and details.

Attributes Summary

columns_required

Columns required by this expression (Set [ ColumnTag ]).

Methods Summary

contains(item)	Construct a boolean column expression that tests whether a scalar expression is present in this container expression.
is_supported_by(engine)	Test whether the given engine is capable of evaluating this expression.
range_literal(r)	Construct a container expression from a range of indices.
sequence(items, dtype)	Construct a container expression from a sequence of item expressions.

Attributes Documentation

columns_required

Columns required by this expression (Set [ ColumnTag ]).

This includes columns required by expressions nested within this one.

Methods Documentation

contains(item: ColumnExpression) → ColumnInContainer

Construct a boolean column expression that tests whether a scalar expression is present in this container expression.

Parameters:

item : ColumnExpression

Item expression to test.

Returns:

contains : ColumnInContainer

Boolean column expression that tests for membership in the container.

is_supported_by(engine: Engine) → bool

Test whether the given engine is capable of evaluating this expression.

Parameters:

engine : Engine

Engine to test.

Returns:

supported : bool

Whether the engine supports this expression and all expressions nested within it.

classmethod range_literal(r: range) → lsst.daf.relation._columns._container.ColumnRangeLiteral

Construct a container expression from a range of indices.

Parameters:

r : range

Range object.

Returns:

container : ColumnRangeLiteral

Container expression object representing the range.

classmethod sequence(items: Sequence[ColumnExpression], dtype: type | None = None) → ColumnExpressionSequence

Construct a container expression from a sequence of item expressions.

Parameters:

items : Sequence [ ColumnExpression ]

Sequence of item expressions.

dtype : type, optional

The Python type of the elements in the container.

Returns:

container : ColumnExpressionSequence

Container expression object backed by the given items.