ConfigField

class lsst.pex.config.ConfigField(doc, dtype, default=None, check=None)

Bases: lsst.pex.config.Field

A configuration field (Field subclass) that takes a Config-type as a value.

Parameters:

doc : str

A description of the configuration field.

dtype : lsst.pex.config.Config-type

The type of the field, which must be a subclass of lsst.pex.config.Config.

default : lsst.pex.config.Config, optional

If default is None, the field will default to a default-constructed instance of dtype. Additionally, to allow for fewer deep-copies, assigning an instance of ConfigField to dtype itself, is considered equivalent to assigning a default-constructed sub-config. This means that the argument default can be dtype, as well as an instance of dtype.

check : callable, optional

A callback function that validates the field’s value, returning True if the value is valid, and False otherwise.

See also

ChoiceField, ConfigChoiceField, ConfigDictField, ConfigurableField, DictField, Field, ListField, RangeField, RegistryField

Notes

The behavior of this type of field is much like that of the base Field type.

Assigning to ConfigField will update all of the fields in the configuration.

Attributes Summary

supportedTypes

Methods Summary

freeze(instance)	Make this field read-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 'complex'>, <class 'bool'>, <class 'int'>, <class 'str'>, <class 'float'>}

Methods Documentation

freeze(instance)

Make this field read-only.

Parameters:

instance : lsst.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:

instance : lsst.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:

outfile : file-like object

A writeable field handle.

instance : Config

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:

instance : Config

The Config that contains this field.

Returns:

value : object

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:

instance : lsst.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.Field.validate if they re-implement validate.