Inheritance diagram for lsst.pex.config.config.Field:

Public Member Functions
def	__init__ (self, doc, dtype, default=None, check=None, optional=False)

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

	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`.

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 179 of file config.py.

Constructor & Destructor Documentation

◆ init()

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

Definition at line 257 of file config.py.

     def __init__(self, doc, dtype, default=None, check=None, optional=False):
         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)
 

Member Function Documentation

◆ delete()

def lsst.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 528 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 lsst.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.

Definition at line 453 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 lsst.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.

Definition at line 471 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 lsst.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.**

Definition at line 350 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 lsst.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`.

Definition at line 300 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 lsst.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.

Definition at line 394 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)
 
         # 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 lsst.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.

Definition at line 426 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 lsst.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`.

Definition at line 321 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

lsst.pex.config.config.Field.check

Definition at line 284 of file config.py.

◆ default

lsst.pex.config.config.Field.default

Definition at line 280 of file config.py.

◆ doc

lsst.pex.config.config.Field.doc

Definition at line 271 of file config.py.

◆ dtype

lsst.pex.config.config.Field.dtype

Definition at line 267 of file config.py.

◆ optional

lsst.pex.config.config.Field.optional

Definition at line 288 of file config.py.

◆ source

lsst.pex.config.config.Field.source

Definition at line 295 of file config.py.

◆ supportedTypes

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

static

Definition at line 253 of file config.py.

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

/j/snowflake/release/lsstsw/stack/Linux64/pex_config/16.0-13-g118c103+3/python/lsst/pex/config/config.py

Public Member Functions

Public Attributes

Static Public Attributes