# Licensed under a 3-clause BSD style license - see LICENSE.rst
from __future__ import annotations
__all__ = ["Parameter"]
import copy
from dataclasses import KW_ONLY, dataclass, field, fields, is_dataclass, replace
from enum import Enum, auto
from typing import TYPE_CHECKING, Any
import astropy.units as u
from ._converter import _REGISTRY_FVALIDATORS, FValidateCallable, _register_validator
if TYPE_CHECKING:
from collections.abc import Sequence
class Sentinel(Enum):
"""Sentinel values for Parameter fields."""
MISSING = auto()
"""A sentinel value signifying a missing default."""
def __repr__(self):
return f"<{self.name}>"
MISSING = Sentinel.MISSING
@dataclass(frozen=True)
class _UnitField:
# TODO: rm this class when py3.13+ allows for `field(converter=...)`
def __get__(
self, obj: Parameter | None, objcls: type[Parameter] | None
) -> u.Unit | None:
if obj is None: # calling `Parameter.unit` from the class
return None
return getattr(obj, "_unit", None)
def __set__(self, obj: Parameter, value: Any) -> None:
object.__setattr__(obj, "_unit", u.Unit(value) if value is not None else None)
@dataclass(frozen=True)
class _FValidateField:
default: FValidateCallable | str = "default"
def __get__(
self, obj: Parameter | None, objcls: type[Parameter] | None
) -> FValidateCallable | str:
if obj is None: # calling `Parameter.fvalidate` from the class
return self.default
return obj._fvalidate # calling `Parameter.fvalidate` from an instance
def __set__(self, obj: Parameter, value: Any) -> None:
# Always store input fvalidate.
object.__setattr__(obj, "_fvalidate_in", value)
# Process to the callable.
if value in _REGISTRY_FVALIDATORS:
value = _REGISTRY_FVALIDATORS[value]
elif isinstance(value, str):
msg = f"`fvalidate`, if str, must be in {_REGISTRY_FVALIDATORS.keys()}"
raise ValueError(msg)
elif not callable(value):
msg = f"`fvalidate` must be a function or {_REGISTRY_FVALIDATORS.keys()}"
raise TypeError(msg)
object.__setattr__(obj, "_fvalidate", value)
[docs]
@dataclass(frozen=True)
class Parameter:
r"""Cosmological parameter (descriptor).
Should only be used with a :class:`~astropy.cosmology.Cosmology` subclass.
Parameters
----------
default : Any (optional, keyword-only)
Default value of the Parameter. If not given the
Parameter must be set when initializing the cosmology.
derived : bool (optional, keyword-only)
Whether the Parameter is 'derived', default `False`.
Derived parameters behave similarly to normal parameters, but are not
sorted by the |Cosmology| signature (probably not there) and are not
included in all methods. For reference, see ``Ode0`` in
``FlatFLRWMixin``, which removes :math:`\Omega_{de,0}`` as an
independent parameter (:math:`\Omega_{de,0} \equiv 1 - \Omega_{tot}`).
unit : unit-like or None (optional, keyword-only)
The `~astropy.units.Unit` for the Parameter. If None (default) no
unit as assumed.
equivalencies : `~astropy.units.Equivalency` or sequence thereof
Unit equivalencies for this Parameter.
fvalidate : callable[[object, object, Any], Any] or str (optional, keyword-only)
Function to validate the Parameter value from instances of the
cosmology class. If "default", uses default validator to assign units
(with equivalencies), if Parameter has units.
For other valid string options, see ``Parameter._registry_validators``.
'fvalidate' can also be set through a decorator with
:meth:`~astropy.cosmology.Parameter.validator`.
doc : str or None (optional, keyword-only)
Parameter description.
Examples
--------
For worked examples see :class:`~astropy.cosmology.FLRW`.
"""
_: KW_ONLY
default: Any = MISSING
"""Default value of the Parameter.
By default set to ``MISSING``, which indicates the parameter must be set
when initializing the cosmology.
"""
derived: bool = False
"""Whether the Parameter can be set, or is derived, on the cosmology."""
# Units
unit: _UnitField = _UnitField()
"""The unit of the Parameter (can be `None` for unitless)."""
equivalencies: u.Equivalency | Sequence[u.Equivalency] = field(default_factory=list)
"""Unit equivalencies available when setting the parameter."""
# Setting
fvalidate: _FValidateField = _FValidateField(default="default")
"""Function to validate/convert values when setting the Parameter."""
# Info
doc: str | None = None
"""Parameter description."""
name: str | None = field(init=False, compare=True, default=None, repr=False)
"""The name of the Parameter on the Cosmology.
Cannot be set directly.
"""
def __post_init__(self) -> None:
self._fvalidate_in: FValidateCallable | str
self._fvalidate: FValidateCallable
object.__setattr__(self, "__doc__", self.doc)
# Now setting a dummy attribute name. The cosmology class will call
# `__set_name__`, passing the real attribute name. However, if Parameter is not
# init'ed as a descriptor then this ensures that all declared fields exist.
self.__set_name__(None, None)
def __set_name__(self, cosmo_cls: type, name: str | None) -> None:
# attribute name on container cosmology class
self._attr_name: str
object.__setattr__(self, "name", name)
object.__setattr__(self, "_attr_name", "_" + (name or ""))
# -------------------------------------------
# descriptor and property-like methods
def __get__(self, cosmology, cosmo_cls=None):
# Get from class
if cosmology is None:
# If the Parameter is being set as part of a dataclass constructor, then we
# raise an AttributeError if the default is MISSING. This is to prevent the
# Parameter from being set as the default value of the dataclass field and
# erroneously included in the class' __init__ signature.
if self.default is MISSING and (
not is_dataclass(cosmo_cls)
or self.name not in cosmo_cls.__dataclass_fields__
):
raise AttributeError
return self
# Get from instance
return getattr(cosmology, self._attr_name)
def __set__(self, cosmology, value):
"""Allows attribute setting once.
Raises AttributeError subsequently.
"""
# Raise error if setting 2nd time.
if hasattr(cosmology, self._attr_name):
raise AttributeError(f"cannot assign to field {self.name!r}")
# Change `self` to the default value if default is MISSING.
# This is done for backwards compatibility only - so that Parameter can be used
# in a dataclass and still return `self` when accessed from a class.
# Accessing the Parameter object via `cosmo_cls.param_name` will be removed
# in favor of `cosmo_cls.parameters["param_name"]`.
if value is self:
value = self.default
# Validate value, generally setting units if present
value = self.validate(cosmology, copy.deepcopy(value))
# Make the value read-only, if ndarray-like
if hasattr(value, "setflags"):
value.setflags(write=False)
# Set the value on the cosmology
object.__setattr__(cosmology, self._attr_name, value)
# -------------------------------------------
# validate value
[docs]
def validator(self, fvalidate):
"""Make new Parameter with custom ``fvalidate``.
Note: ``Parameter.fvalidator`` must be the top-most descriptor decorator.
Parameters
----------
fvalidate : callable[[type, type, Any], Any]
Returns
-------
`~astropy.cosmology.Parameter`
Copy of this Parameter but with custom ``fvalidate``.
"""
return self.clone(fvalidate=fvalidate)
[docs]
def validate(self, cosmology, value):
"""Run the validator on this Parameter.
Parameters
----------
cosmology : `~astropy.cosmology.Cosmology` instance
value : Any
The object to validate.
Returns
-------
Any
The output of calling ``fvalidate(cosmology, self, value)``
(yes, that parameter order).
"""
return self._fvalidate(cosmology, self, value)
[docs]
@staticmethod
def register_validator(key, fvalidate=None):
"""Decorator to register a new kind of validator function.
Parameters
----------
key : str
fvalidate : callable[[object, object, Any], Any] or None, optional
Value validation function.
Returns
-------
``validator`` or callable[``validator``]
if validator is None returns a function that takes and registers a
validator. This allows ``register_validator`` to be used as a
decorator.
"""
return _register_validator(key, fvalidate=fvalidate)
# -------------------------------------------
[docs]
def clone(self, **kw):
"""Clone this `Parameter`, changing any constructor argument.
Parameters
----------
**kw
Passed to constructor. The current values, eg. ``fvalidate`` are
used as the default values, so an empty ``**kw`` is an exact copy.
Examples
--------
>>> p = Parameter()
>>> p
Parameter(derived=False, unit=None, equivalencies=[],
fvalidate='default', doc=None)
>>> p.clone(unit="km")
Parameter(derived=False, unit=Unit("km"), equivalencies=[],
fvalidate='default', doc=None)
"""
kw.setdefault("fvalidate", self._fvalidate_in) # prefer the input fvalidate
cloned = replace(self, **kw)
# Transfer over the __set_name__ stuff. If `clone` is used to make a
# new descriptor, __set_name__ will be called again, overwriting this.
cloned.__set_name__(None, self.name)
return cloned
def __repr__(self) -> str:
"""Return repr(self)."""
fields_repr = (
# Get the repr, using the input fvalidate over the processed value
f"{f.name}={(getattr(self, f.name if f.name != 'fvalidate' else '_fvalidate_in'))!r}"
for f in fields(self)
# Only show fields that should be displayed and are not sentinel values
if f.repr and (f.name != "default" or self.default is not MISSING)
)
return f"{self.__class__.__name__}({', '.join(fields_repr)})"
