ThresholdSpecification

class lsst.verify.ThresholdSpecification(name, threshold, operator_str, **kwargs)

Bases: Specification

A threshold-type specification, associated with a Metric, that defines a binary comparison against a measurement.

Parameters

namestr

Name of the specification for a metric. LPM-17, for example, uses 'design', 'minimum' and 'stretch' terminology.

quantityastropy.units.Quantity

The specification threshold level.

operator_strstr

The threshold’s binary comparison operator. The operator is oriented so that measurement {{ operator }} threshold quantity is the specification test. Can be one of: '<', '<=', '>', '>=', '==', or '!='.

metadata_querydict, optional

Dictionary of key-value terms that the measurement’s metadata must have for this specification to apply.

tagssequence of str, optional

Sequence of tags that group this specification with others.

kwargsdict

Keyword arguments passed directly to the lsst.validate.base.Specification constructor.

Raises

TypeError

If name is not compartible with Name, or threshold is not a Quantity, or if the operator_str cannot be converted into a Python binary comparison operator.

Attributes Summary

datum	Representation of this ThresholdSpecification's threshold as a Datum.
operator	Binary comparision operator that tests success of a measurement fulfilling a specification of this metric.
operator_str	Threshold comparision operator ('str').
threshold	The specification threshold level (astropy.units.Quantity).
type	Specification type (str).

Methods Summary

check(measurement)	Check if a measurement passes this specification.
convert_operator_str(op_str)	Convert a string representing a binary comparison operator to the operator function itself.
deserialize([name, threshold, metric, package])	Deserialize from keys in a specification YAML document or a JSON serialization into a ThresholdSpecification instance.

Attributes Documentation

datum

Representation of this ThresholdSpecification‘s threshold as a Datum.

operator

Binary comparision operator that tests success of a measurement fulfilling a specification of this metric.

Measured value is on left side of comparison and specification level is on right side.

operator_str

Threshold comparision operator (‘str’).

A measurement passes the specification if:

measurement {{ operator }} threshold == True

The operator string is a standard Python binary comparison token, such as: '<', '>', '<=', '>=', '==' or '!='.

threshold = None

The specification threshold level (astropy.units.Quantity).

type

Methods Documentation

check(measurement)

Check if a measurement passes this specification.

Parameters

measurementastropy.units.Quantity

The measurement value. The measurement Quantity must have units compatible with threshold.

Returns

passedbool

True if the measurement meets the specification, False otherwise.

Raises

astropy.units.UnitError

Raised if the measurement cannot be compared to the threshold. For example, if the measurement is not an astropy.units.Quantity or if the units are not compatible.

static convert_operator_str(op_str)

Convert a string representing a binary comparison operator to the operator function itself.

Operators are oriented so that the measurement is on the left-hand side, and specification threshold on the right hand side.

The following operators are permitted:

op_str	Function
>=	operator.ge
>	operator.gt
<	operator.lt
<=	operator.le
==	operator.eq
!=	operator.ne

Parameters

op_strstr

A string representing a binary operator.

Returns

op_funcobj

An operator function from the operator standard library module.

Raises

ValueError

Raised if op_str is not a supported binary comparison operator.

classmethod deserialize(name=None, threshold=None, metric=None, package=None, **kwargs)

Deserialize from keys in a specification YAML document or a JSON serialization into a ThresholdSpecification instance.

Parameters

namestr or lsst.validate.base.Name

Specification name, either as a string or Name.

thresholddict

A dict with fields:

• 'value': threshold value (float or int).

• 'unit': threshold unit, as an astropy.units.Unit- compatible str.

• 'operator': a binary comparison operator, described in the class parameters documentation (str).

metricstr or lsst.validate.base.Name, optional

Name of the fully-qualified name of the metric the specification corresponds to. This parameter is optional if name is already fully-qualified.

packagestr or lsst.validate.base.Name, optional

Name of the package the specification corresponds to. This parameter is optional if name or metric are already fully-qualified.

kwargsdict

Keyword arguments passed directly to the lsst.validate.base.Specification constructor.

Returns

specificationThresholdSpecification

A specification instance.