ChoiceField

class lsst.pex.config.ChoiceField(doc, dtype=None, allowed=None, default=None, optional=True, deprecated=None)

Bases: Field[FieldTypeVar]

A configuration field (Field subclass) that allows a user to select from a predefined set of values.

Use ChoiceField when a configuration can only take one of a predefined set of values. Each choice must be of the same type.

Parameters:

docstr

Documentation string that describes the configuration field.

dtypeclass

The type of the field’s choices. For example, str or int.

alloweddict

The allowed values. Keys are the allowed choices (of dtype-type). Values are descriptions (str-type) of each choice.

defaultdtype-type, optional

The default value, which is of type dtype and one of the allowed choices.

optionalbool, optional

If True, this configuration field is optional. Default is True.

deprecatedNone or str, optional

A description of why this Field is deprecated, including removal date. If not None, the string is appended to the docstring for this Field.

See also

ConfigChoiceField

ConfigDictField

ConfigField

ConfigurableField

DictField

Field

ListField

RangeField

RegistryField

Attributes Summary

supportedTypes

Supported data types for field values (set of types).

Methods Summary

freeze(instance)	Make this field read-only (for internal use only).
rename(instance)	Rename the field in a Config (for internal use only).
save(outfile, instance)	Save this field to a file (for internal use only).
toDict(instance)	Convert the field value so that it can be set as the value of an item in a dict (for internal use only).
validate(instance)	Validate the field (for internal use only).

Attributes Documentation

supportedTypes = {<class 'float'>, <class 'complex'>, <class 'bool'>, <class 'int'>, <class 'str'>}

Supported data types for field values (set of types).

Methods Documentation

freeze(instance)

Make this field read-only (for internal use only).

Parameters:

instancelsst.pex.config.Config

The config instance that contains this field.

Notes

Freezing is only relevant for fields that hold subconfigs. Fields which hold subconfigs should freeze each subconfig.

Subclasses should implement this method.

rename(instance)

Rename the field in a Config (for internal use only).

Parameters:

instancelsst.pex.config.Config

The config instance that contains this field.

Notes

This method is invoked by the lsst.pex.config.Config object that contains this field and should not be called directly.

Renaming is only relevant for Field instances that hold subconfigs. Fields that hold subconfigs should rename each subconfig with the full field name as generated by lsst.pex.config.config._joinNamePath.

save(outfile, instance)

Save this field to a file (for internal use only).

Parameters:

outfilefile-like object

A writeable field handle.

instanceConfig

The Config instance that contains this field.

Notes

This method is invoked by the Config object that contains this field and should not be called directly.

The output consists of the documentation string (lsst.pex.config.Field.doc) formatted as a Python comment. The second line is formatted as an assignment: {fullname}={value}.

This output can be executed with Python.

toDict(instance)

Convert the field value so that it can be set as the value of an item in a dict (for internal use only).

Parameters:

instanceConfig

The Config that contains this field.

Returns:

valueobject

The field’s value. See Notes.

Notes

This method invoked by the owning Config object and should not be called directly.

Simple values are passed through. Complex data structures must be manipulated. For example, a Field holding a subconfig should, instead of the subconfig object, return a dict where the keys are the field names in the subconfig, and the values are the field values in the subconfig.

validate(instance)

Validate the field (for internal use only).

Parameters:

instancelsst.pex.config.Config

The config instance that contains this field.

Raises:

lsst.pex.config.FieldValidationError

Raised if verification fails.

Notes

This method provides basic validation:

• Ensures that the value is not None if the field is not optional.

• Ensures type correctness.

• Ensures that the user-provided check function is valid.

Most Field subclasses should call lsst.pex.config.Field.validate if they re-implement validate.