pex.config.config.Field Class Reference

Inheritance diagram for pex.config.config.Field:

Public Member Functions
def	__init__ (self, doc, dtype, default=None, check=None, optional=False, deprecated=None)
def	rename (self, instance)
def	validate (self, instance)
def	freeze (self, instance)
def	save (self, outfile, instance)
def	toDict (self, instance)
def	__get__ (self, instance, owner=None, at=None, label="default")
def	__set__ (self, instance, value, at=None, label='assignment')
def	__delete__ (self, instance, at=None, label='deletion')

Public Attributes
	dtype
	doc
	deprecated
	default
	check
	optional
	source

Static Public Attributes
	supportedTypes = set((str, bool, float, int, complex))

Detailed Description

A field in a `~lsst.pex.config.Config` that supports `int`, `float`,
`complex`, `bool`, and `str` data types.

Parameters
----------
doc : `str`
    A description of the field for users.
dtype : type
    The field's data type. ``Field`` only supports basic data types:
    `int`, `float`, `complex`, `bool`, and `str`. See
    `Field.supportedTypes`.
default : object, optional
    The field's default value.
check : callable, optional
    A callable that is called with the field's value. This callable should
    return `False` if the value is invalid. More complex inter-field
    validation can be written as part of the
    `lsst.pex.config.Config.validate` method.
optional : `bool`, optional
    This sets whether the field is considered optional, and therefore
    doesn't need to be set by the user. When `False`,
    `lsst.pex.config.Config.validate` fails if the field's value is `None`.
deprecated : None 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.

Raises
------
ValueError
    Raised when the ``dtype`` parameter is not one of the supported types
    (see `Field.supportedTypes`).

See also
--------
ChoiceField
ConfigChoiceField
ConfigDictField
ConfigField
ConfigurableField
DictField
ListField
RangeField
RegistryField

Notes
-----
``Field`` instances (including those of any subclass of ``Field``) are used
as class attributes of `~lsst.pex.config.Config` subclasses (see the
example, below). ``Field`` attributes work like the `property` attributes
of classes that implement custom setters and getters. `Field` attributes
belong to the class, but operate on the instance. Formally speaking,
`Field` attributes are `descriptors
<https://docs.python.org/3/howto/descriptor.html>`_.

When you access a `Field` attribute on a `Config` instance, you don't
get the `Field` instance itself. Instead, you get the value of that field,
which might be a simple type (`int`, `float`, `str`, `bool`) or a custom
container type (like a `lsst.pex.config.List`) depending on the field's
type. See the example, below.

Examples
--------
Instances of ``Field`` should be used as class attributes of
`lsst.pex.config.Config` subclasses:

>>> from lsst.pex.config import Config, Field
>>> class Example(Config):
...     myInt = Field("An integer field.", int, default=0)
...
>>> print(config.myInt)
0
>>> config.myInt = 5
>>> print(config.myInt)
5

Definition at line 195 of file config.py.

Constructor & Destructor Documentation

__init__()

def pex.config.config.Field.__init__	(		self,
			doc,
			dtype,
			default = None,
			check = None,
			optional = False,
			deprecated = None
	)

Reimplemented in pex.config.configChoiceField.ConfigChoiceField, pex.config.configurableField.ConfigurableField, and pex.config.choiceField.ChoiceField.

Definition at line 276 of file config.py.

    def __init__(self, doc, dtype, default=None, check=None, optional=False, deprecated=None):
        if dtype not in self.supportedTypes:
            raise ValueError("Unsupported Field dtype %s" % _typeStr(dtype))
 
        source = getStackFrame()
        self._setup(doc=doc, dtype=dtype, default=default, check=check, optional=optional, source=source,
                    deprecated=deprecated)
 

Member Function Documentation

__delete__()

def pex.config.config.Field.__delete__	(		self,
			instance,
			at = None,
			label = 'deletion'
	)

Delete an attribute from a `lsst.pex.config.Config` instance.

Parameters
----------
instance : `lsst.pex.config.Config`
    The config instance that contains this field.
at : `list` of `lsst.pex.config.callStack.StackFrame`
    The call stack (created by
    `lsst.pex.config.callStack.getCallStack`).
label : `str`, optional
    Event label for the history.

Notes
-----
This is invoked by the owning `~lsst.pex.config.Config` object and
should not be called directly.

Definition at line 573 of file config.py.

    def __delete__(self, instance, at=None, label='deletion'):
        """Delete an attribute from a `lsst.pex.config.Config` instance.
 
        Parameters
        ----------
        instance : `lsst.pex.config.Config`
            The config instance that contains this field.
        at : `list` of `lsst.pex.config.callStack.StackFrame`
            The call stack (created by
            `lsst.pex.config.callStack.getCallStack`).
        label : `str`, optional
            Event label for the history.
 
        Notes
        -----
        This is invoked by the owning `~lsst.pex.config.Config` object and
        should not be called directly.
        """
        if at is None:
            at = getCallStack()
        self.__set__(instance, None, at=at, label=label)
 

__get__()

def pex.config.config.Field.__get__	(		self,
			instance,
			owner = None,
			at = None,
			label = "default"
	)

Define how attribute access should occur on the Config instance
This is invoked by the owning config object and should not be called
directly

When the field attribute is accessed on a Config class object, it
returns the field object itself in order to allow inspection of
Config classes.

When the field attribute is access on a config instance, the actual
value described by the field (and held by the Config instance) is
returned.

Reimplemented in pex.config.configurableField.ConfigurableField.

Definition at line 498 of file config.py.

    def __get__(self, instance, owner=None, at=None, label="default"):
        """Define how attribute access should occur on the Config instance
        This is invoked by the owning config object and should not be called
        directly
 
        When the field attribute is accessed on a Config class object, it
        returns the field object itself in order to allow inspection of
        Config classes.
 
        When the field attribute is access on a config instance, the actual
        value described by the field (and held by the Config instance) is
        returned.
        """
        if instance is None or not isinstance(instance, Config):
            return self
        else:
            return instance._storage[self.name]
 

__set__()

def pex.config.config.Field.__set__	(		self,
			instance,
			value,
			at = None,
			label = 'assignment'
	)

Set an attribute on the config instance.

Parameters
----------
instance : `lsst.pex.config.Config`
    The config instance that contains this field.
value : obj
    Value to set on this field.
at : `list` of `lsst.pex.config.callStack.StackFrame`
    The call stack (created by
    `lsst.pex.config.callStack.getCallStack`).
label : `str`, optional
    Event label for the history.

Notes
-----
This method is invoked by the owning `lsst.pex.config.Config` object
and should not be called directly.

Derived `~lsst.pex.config.Field` classes may need to override the
behavior. When overriding ``__set__``, `~lsst.pex.config.Field` authors
should follow the following rules:

- Do not allow modification of frozen configs.
- Validate the new value **before** modifying the field. Except if the
  new value is `None`. `None` is special and no attempt should be made
  to validate it until `lsst.pex.config.Config.validate` is called.
- Do not modify the `~lsst.pex.config.Config` instance to contain
  invalid values.
- If the field is modified, update the history of the
  `lsst.pex.config.field.Field` to reflect the changes.

In order to decrease the need to implement this method in derived
`~lsst.pex.config.Field` types, value validation is performed in the
`lsst.pex.config.Field._validateValue`. If only the validation step
differs in the derived `~lsst.pex.config.Field`, it is simpler to
implement `lsst.pex.config.Field._validateValue` than to reimplement
``__set__``. More complicated behavior, however, may require
reimplementation.

Reimplemented in pex.config.configChoiceField.ConfigChoiceField, pex.config.listField.ListField, pex.config.configurableField.ConfigurableField, pex.config.dictField.DictField, and pex.config.configField.ConfigField.

Definition at line 516 of file config.py.

    def __set__(self, instance, value, at=None, label='assignment'):
        """Set an attribute on the config instance.
 
        Parameters
        ----------
        instance : `lsst.pex.config.Config`
            The config instance that contains this field.
        value : obj
            Value to set on this field.
        at : `list` of `lsst.pex.config.callStack.StackFrame`
            The call stack (created by
            `lsst.pex.config.callStack.getCallStack`).
        label : `str`, optional
            Event label for the history.
 
        Notes
        -----
        This method is invoked by the owning `lsst.pex.config.Config` object
        and should not be called directly.
 
        Derived `~lsst.pex.config.Field` classes may need to override the
        behavior. When overriding ``__set__``, `~lsst.pex.config.Field` authors
        should follow the following rules:
 
        - Do not allow modification of frozen configs.
        - Validate the new value **before** modifying the field. Except if the
          new value is `None`. `None` is special and no attempt should be made
          to validate it until `lsst.pex.config.Config.validate` is called.
        - Do not modify the `~lsst.pex.config.Config` instance to contain
          invalid values.
        - If the field is modified, update the history of the
          `lsst.pex.config.field.Field` to reflect the changes.
 
        In order to decrease the need to implement this method in derived
        `~lsst.pex.config.Field` types, value validation is performed in the
        `lsst.pex.config.Field._validateValue`. If only the validation step
        differs in the derived `~lsst.pex.config.Field`, it is simpler to
        implement `lsst.pex.config.Field._validateValue` than to reimplement
        ``__set__``. More complicated behavior, however, may require
        reimplementation.
        """
        if instance._frozen:
            raise FieldValidationError(self, instance, "Cannot modify a frozen Config")
 
        history = instance._history.setdefault(self.name, [])
        if value is not None:
            value = _autocast(value, self.dtype)
            try:
                self._validateValue(value)
            except BaseException as e:
                raise FieldValidationError(self, instance, str(e))
 
        instance._storage[self.name] = value
        if at is None:
            at = getCallStack()
        history.append((value, at, label))
 

freeze()

def pex.config.config.Field.freeze	(		self,
			instance
	)

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

Reimplemented in pex.config.configChoiceField.ConfigChoiceField, pex.config.configurableField.ConfigurableField, pex.config.configDictField.ConfigDictField, and pex.config.configField.ConfigField.

Definition at line 377 of file config.py.

    def freeze(self, instance):
        """Make this field read-only (for internal use 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.**
        """
        pass
 

rename()

def pex.config.config.Field.rename	(		self,
			instance
	)

Rename the field in a `~lsst.pex.config.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 `~lsst.pex.config.Field` instances that
hold subconfigs. `~lsst.pex.config.Fields` that hold subconfigs should
rename each subconfig with the full field name as generated by
`lsst.pex.config.config._joinNamePath`.

Reimplemented in pex.config.configChoiceField.ConfigChoiceField, pex.config.configurableField.ConfigurableField, pex.config.configDictField.ConfigDictField, and pex.config.configField.ConfigField.

Definition at line 327 of file config.py.

    def rename(self, instance):
        """Rename the field in a `~lsst.pex.config.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 `~lsst.pex.config.Field` instances that
        hold subconfigs. `~lsst.pex.config.Fields` that hold subconfigs should
        rename each subconfig with the full field name as generated by
        `lsst.pex.config.config._joinNamePath`.
        """
        pass
 

save()

def pex.config.config.Field.save	(		self,
			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 `~lsst.pex.config.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.

Reimplemented in pex.config.configChoiceField.ConfigChoiceField, pex.config.configurableField.ConfigurableField, pex.config.configDictField.ConfigDictField, and pex.config.configField.ConfigField.

Definition at line 435 of file config.py.

    def save(self, 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 `~lsst.pex.config.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.
        """
        value = self.__get__(instance)
        fullname = _joinNamePath(instance._name, self.name)
 
        if self.deprecated and value == self.default:
            return
 
        # write full documentation string as comment lines
        # (i.e. first character is #)
        doc = "# " + str(self.doc).replace("\n", "\n# ")
        if isinstance(value, float) and (math.isinf(value) or math.isnan(value)):
            # non-finite numbers need special care
            outfile.write(u"{}\n{}=float('{!r}')\n\n".format(doc, fullname, value))
        else:
            outfile.write(u"{}\n{}={!r}\n\n".format(doc, fullname, value))
 

toDict()

def pex.config.config.Field.toDict	(		self,
			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 `~lsst.pex.config.Config` object and
should not be called directly.

Simple values are passed through. Complex data structures must be
manipulated. For example, a `~lsst.pex.config.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.

Reimplemented in pex.config.configChoiceField.ConfigChoiceField, pex.config.listField.ListField, pex.config.configurableField.ConfigurableField, pex.config.dictField.DictField, pex.config.configField.ConfigField, and pex.config.configDictField.ConfigDictField.

Definition at line 471 of file config.py.

    def toDict(self, 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 `~lsst.pex.config.Config` object and
        should not be called directly.
 
        Simple values are passed through. Complex data structures must be
        manipulated. For example, a `~lsst.pex.config.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.
        """
        return self.__get__(instance)
 

validate()

def pex.config.config.Field.validate	(		self,
			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 `~lsst.pex.config.Field` subclasses should call
`lsst.pex.config.field.Field.validate` if they re-implement
`~lsst.pex.config.field.Field.validate`.

Reimplemented in pex.config.configChoiceField.ConfigChoiceField, pex.config.configurableField.ConfigurableField, pex.config.listField.ListField, pex.config.configField.ConfigField, pex.config.dictField.DictField, and pex.config.configDictField.ConfigDictField.

Definition at line 348 of file config.py.

    def validate(self, 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 `~lsst.pex.config.Field` subclasses should call
        `lsst.pex.config.field.Field.validate` if they re-implement
        `~lsst.pex.config.field.Field.validate`.
        """
        value = self.__get__(instance)
        if not self.optional and value is None:
            raise FieldValidationError(self, instance, "Required value cannot be None")
 

Member Data Documentation

check

pex.config.config.Field.check

Definition at line 311 of file config.py.

default

pex.config.config.Field.default

Definition at line 307 of file config.py.

deprecated

pex.config.config.Field.deprecated

Definition at line 298 of file config.py.

doc

pex.config.config.Field.doc

Definition at line 294 of file config.py.

dtype

pex.config.config.Field.dtype

Definition at line 287 of file config.py.

optional

pex.config.config.Field.optional

Definition at line 315 of file config.py.

source

pex.config.config.Field.source

Definition at line 322 of file config.py.

supportedTypes

pex.config.config.Field.supportedTypes = set((str, bool, float, int, complex))

static

Definition at line 272 of file config.py.

---

The documentation for this class was generated from the following file:

• /j/snowflake/release/lsstsw/stack/cb4e2dc/Linux64/pex_config/20.0.0+34a42eae2c/python/lsst/pex/config/config.py