ExpressionFactory

class lsst.daf.butler.queries.expression_factory.ExpressionFactory(universe: DimensionUniverse)

Bases: object

A factory for creating column expressions that uses operator overloading to form a mini-language.

Instances of this class are usually obtained from Query.expression_factory; see that property’s documentation for more information.

Parameters

universeDimensionUniverse

Object that describes all dimensions.

Methods Summary

all(first, /, *args)	Combine a sequence of boolean expressions with logical AND.
any(first, /, *args)	Combine a sequence of boolean expressions with logical OR.
literal(value)	Return an expression proxy that represents a literal value.
not_(operand)	Apply a logical NOT operation to a boolean expression.
unwrap(proxy)	Return the column expression object that backs a proxy.

Methods Documentation

all(first: Predicate, /, *args: Predicate) → Predicate

Combine a sequence of boolean expressions with logical AND.

Parameters

firsttree.Predicate

First operand (required).

*args

Additional operands.

Returns

logical_andtree.Predicate

A boolean expression that evaluates to True only if all operands evaluate to `True.

any(first: Predicate, /, *args: Predicate) → Predicate

Combine a sequence of boolean expressions with logical OR.

Parameters

firsttree.Predicate

First operand (required).

*args

Additional operands.

Returns

logical_ortree.Predicate

A boolean expression that evaluates to True if any operand evaluates to `True.

static literal(value: object) → ExpressionProxy

Return an expression proxy that represents a literal value.

Expression proxy objects obtained from this factory can generally be compared directly to literals, so calling this method directly in user code should rarely be necessary.

Parameters

valueobject

Value to include as a literal in an expression tree.

Returns

expressionExpressionProxy

Expression wrapper for this literal.

not_(operand: Predicate) → Predicate

Apply a logical NOT operation to a boolean expression.

Parameters

operandtree.Predicate

Expression to invetree.

Returns

logical_nottree.Predicate

A boolean expression that evaluates to the opposite of operand.

static unwrap(proxy: ExpressionProxy) → Annotated[IntColumnLiteral | StringColumnLiteral | FloatColumnLiteral | HashColumnLiteral | UUIDColumnLiteral | DateTimeColumnLiteral | TimespanColumnLiteral | RegionColumnLiteral | DimensionKeyReference | DimensionFieldReference | DatasetFieldReference | UnaryExpression | BinaryExpression, FieldInfo(annotation=NoneType, required=True, discriminator='expression_type')]

Return the column expression object that backs a proxy.

Parameters

proxyExpressionProxy

Proxy constructed via an ExpressionFactory.

Returns

expressiontree.ColumnExpression

Underlying column expression object.