ColumnReference¶
- class lsst.daf.relation.ColumnReference(tag: ColumnTag, dtype: type | None)¶
Bases:
ColumnExpression
A concrete column expression that refers to a relation column.
Attributes Summary
Methods Summary
eq
(other)Construct a boolean equality-comparison expression.
function
(name, *args[, dtype, ...])Construct an expression that represents a function call with expression arguments.
ge
(other)Construct a boolean greater-or-equal-comparison expression.
gt
(other)Construct a boolean greater-than-comparison expression.
is_supported_by
(engine)Test whether the given engine is capable of evaluating this expression.
le
(other)Construct a boolean less-or-equal-comparison expression.
literal
(value[, dtype])Construct an expression backed by a regular Python object.
lt
(other)Construct a boolean less-than-comparison expression.
method
(name, *args[, dtype, ...])Construct an expression that represents a method call with expression arguments.
ne
(other)Construct a boolean inequality-comparison expression.
predicate_function
(name, *args[, ...])Construct an expression that represents a function call with expression arguments and a boolean result.
predicate_method
(name, *args[, ...])Construct an expression that represents a method call with expression arguments and a boolean result.
reference
(tag[, dtype])Construct an expression that refers to a column in a relation.
Attributes Documentation
- columns_required¶
Methods Documentation
- eq(other: ColumnExpression) PredicateFunction ¶
Construct a boolean equality-comparison expression.
- Parameters:
- other
ColumnExpression
Expression whose value will be compared to that of
self
.
- other
- Returns:
- comparison
Predicate
Boolean column expression.
- comparison
- classmethod function(name: str, *args: ColumnExpression, dtype: type | None = None, supporting_engine_types: Iterable[type[Engine]] | None = None) ColumnFunction ¶
Construct an expression that represents a function call with expression arguments.
- Parameters:
- name
str
Name of the method, to be interpreted by the
Engine
or other algorithm.- *args
ColumnExpression
Expressions to pass as arguments to the method (not including
self
; this is aclassmethod
, so it never has access toself
).- dtype
type
orNone
, optional The Python type this expression evaluates to (
type
orNone
).- supporting_engine_types
Iterable
[type
], optional If provided, the set of
Engine
types that are expected to support this expression. IfNone
(default), all engines are assumed to support it.
- name
- Returns:
- function
ColumnFunction
Column expression that represents this function call.
- function
- ge(other: ColumnExpression) PredicateFunction ¶
Construct a boolean greater-or-equal-comparison expression.
- Parameters:
- other
ColumnExpression
Expression whose value will be compared to that of
self
.
- other
- Returns:
- comparison
Predicate
Boolean column expression.
- comparison
- gt(other: ColumnExpression) PredicateFunction ¶
Construct a boolean greater-than-comparison expression.
- Parameters:
- other
ColumnExpression
Expression whose value will be compared to that of
self
.
- other
- Returns:
- comparison
Predicate
Boolean column expression.
- comparison
- is_supported_by(engine: Engine) bool ¶
Test whether the given engine is capable of evaluating this expression.
- le(other: ColumnExpression) PredicateFunction ¶
Construct a boolean less-or-equal-comparison expression.
- Parameters:
- other
ColumnExpression
Expression whose value will be compared to that of
self
.
- other
- Returns:
- comparison
Predicate
Boolean column expression.
- comparison
- classmethod literal(value: Any, dtype: type | None = None) ColumnLiteral ¶
Construct an expression backed by a regular Python object.
- Parameters:
- Returns:
- literal
ColumnLiteral
A column expression backed by the given value.
- literal
- lt(other: ColumnExpression) PredicateFunction ¶
Construct a boolean less-than-comparison expression.
- Parameters:
- other
ColumnExpression
Expression whose value will be compared to that of
self
.
- other
- Returns:
- comparison
Predicate
Boolean column expression.
- comparison
- method(name: str, *args: ColumnExpression, dtype: type | None = None, supporting_engine_types: Iterable[type[Engine]] | None = None) ColumnFunction ¶
Construct an expression that represents a method call with expression arguments.
- Parameters:
- name
str
Name of the method, to be interpreted by the
Engine
or other algorithm.- *args
ColumnExpression
Expressions to pass as arguments to the method (after
self
).- dtype
type
orNone
, optional The Python type this expression evaluates to (
type
orNone
).- supporting_engine_types
Iterable
[type
], optional If provided, the set of
Engine
types that are expected to support this expression. IfNone
(default), all engines are assumed to support it.
- name
- Returns:
- function
ColumnFunction
Column expression that represents this function call.
- function
Notes
ColumnExpression
cannot actually force an engine to interpret the given name as the name of a method rather than something else; calling this method like this:a.method("name", b)
is exactly equivalent to:
ColumnExpression.function("name", a, b)
The provided
iteration
andsql
engines both interpret these names as method names if and only if they are not first found in the built-inoperator
module.
- ne(other: ColumnExpression) PredicateFunction ¶
Construct a boolean inequality-comparison expression.
- Parameters:
- other
ColumnExpression
Expression whose value will be compared to that of
self
.
- other
- Returns:
- comparison
Predicate
Boolean column expression.
- comparison
- classmethod predicate_function(name: str, *args: ColumnExpression, supporting_engine_types: Iterable[type[Engine]] | None = None) PredicateFunction ¶
Construct an expression that represents a function call with expression arguments and a boolean result.
- Parameters:
- name
str
Name of the method, to be interpreted by the
Engine
or other algorithm.- *args
ColumnExpression
Expressions to pass as arguments to the method (not including
self
; this is aclassmethod
, so it never has access toself
).- dtype
type
orNone
, optional The Python type this expression evaluates to (
type
orNone
).- supporting_engine_types
Iterable
[type
], optional If provided, the set of
Engine
types that are expected to support this expression. IfNone
(default), all engines are assumed to support it.
- name
- Returns:
- function
PredicateFunction
Boolean column expression that represents this function call.
- function
- predicate_method(name: str, *args: ColumnExpression, supporting_engine_types: Set[type[Engine]] | None = None) PredicateFunction ¶
Construct an expression that represents a method call with expression arguments and a boolean result.
- Parameters:
- name
str
Name of the method, to be interpreted by the
Engine
or other algorithm.- *args
ColumnExpression
Expressions to pass as arguments to the method (after
self
).- dtype
type
orNone
, optional The Python type this expression evaluates to (
type
orNone
).- supporting_engine_types
Iterable
[type
] optional If provided, the set of
Engine
types that are expected to support this expression. IfNone
(default), all engines are assumed to support it.
- name
- Returns:
- function
PredicateFunction
Boolean column expression that represents this function call.
- function
Notes
ColumnExpression
cannot actually force an engine to interpret the given name as the name of a method rather than something else; calling this method like this:a.predicate_method("name", b)
is exactly equivalent to:
ColumnExpression.predicate_function("name", a, b)
The provided
iteration
andsql
engines both interpret these names as method names if and only if they are not first found in the built-inoperator
module.
- classmethod reference(tag: ColumnTag, dtype: type | None = None) ColumnReference ¶
Construct an expression that refers to a column in a relation.