ThresholdSpecification¶

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

Bases: lsst.verify.Specification

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

Parameters:

name : str: Name of the specification for a metric. LPM-17, for example, uses 'design', 'minimum' and 'stretch' terminology.
quantity : astropy.units.Quantity: The specification threshold level.
operator_str : str: 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_query : dict, optional: Dictionary of key-value terms that the measurement’s metadata must have for this specification to apply.
tags : sequence of str, optional: Sequence of tags that group this specification with others.
kwargs : dict: 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¶: Specification type (str).

Methods Documentation

check(measurement)¶

Check if a measurement passes this specification.

Parameters:	measurement : `astropy.units.Quantity` The measurement value. The measurement `Quantity` must have units compatible with `threshold`.
Returns:	passed : `bool` `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_str : `str` A string representing a binary operator.
Returns:	op_func : obj 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:

name : str or lsst.validate.base.Name

Specification name, either as a string or Name.

threshold : dict

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).

metric : str 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.

package : str 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.

kwargs : dict

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

Returns:

specification : ThresholdSpecification: A specification instance.

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ThresholdSpecification¶