Source code for astropy.cosmology.parameter

# Licensed under a 3-clause BSD style license - see LICENSE.rst

import astropy.units as u
from astropy.utils.decorators import classproperty

__all__ = ["Parameter"]


[docs]class Parameter: r"""Cosmological parameter (descriptor). Should only be used with a :class:`~astropy.cosmology.Cosmology` subclass. Parameters ---------- fvalidate : callable[[object, object, Any], Any] or str, optional 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 Parameter description. 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. fmt : str (optional, keyword-only) `format` specification, used when making string representation of the containing Cosmology. See https://docs.python.org/3/library/string.html#formatspec 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}`). Examples -------- For worked examples see :class:`~astropy.cosmology.FLRW`. """ _registry_validators = {} def __init__(self, fvalidate="default", doc=None, *, unit=None, equivalencies=[], fmt=".3g", derived=False): # parse registered fvalidate if callable(fvalidate): pass elif fvalidate in self._registry_validators: fvalidate = self._registry_validators[fvalidate] elif isinstance(fvalidate, str): raise ValueError("`fvalidate`, if str, must be in " f"{self._registry_validators.keys()}") else: raise TypeError("`fvalidate` must be a function or " f"{self._registry_validators.keys()}") self.__doc__ = doc self._fvalidate = fvalidate # units stuff self._unit = u.Unit(unit) if unit is not None else None self._equivalencies = equivalencies # misc self._fmt = str(fmt) self._derived = derived def __set_name__(self, cosmo_cls, name): # attribute name self._attr_name = name self._attr_name_private = "_" + name @property def name(self): """Parameter name.""" return self._attr_name @property def unit(self): """Parameter unit.""" return self._unit @property def equivalencies(self): """Equivalencies used when initializing Parameter.""" return self._equivalencies @property def format_spec(self): """String format specification.""" return self._fmt @property def derived(self): """Whether the Parameter is derived; true parameters are not.""" return self._derived # ------------------------------------------- # descriptor and property-like methods def __get__(self, cosmology, cosmo_cls=None): # get from class if cosmology is None: return self return getattr(cosmology, self._attr_name_private) def __set__(self, cosmology, value): """Allows attribute setting once. Raises AttributeError subsequently.""" # raise error if setting 2nd time. if hasattr(cosmology, self._attr_name_private): raise AttributeError("can't set attribute") # validate value, generally setting units if present value = self.validate(cosmology, value) setattr(cosmology, self._attr_name_private, value) # ------------------------------------------- # validate value @property def fvalidate(self): """Function to validate a potential value of this Parameter..""" return self._fvalidate
[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``. """ desc = type(self)(fvalidate=fvalidate, doc=self.__doc__, fmt=self.format_spec, unit=self.unit, equivalencies=self.equivalencies, derived=self.derived) return desc
[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] @classmethod def register_validator(cls, 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. """ if key in cls._registry_validators: raise KeyError(f"validator {key!r} already registered with Parameter.") # fvalidate directly passed if fvalidate is not None: cls._registry_validators[key] = fvalidate return fvalidate # for use as a decorator def register(fvalidate): """Register validator function. Parameters ---------- fvalidate : callable[[object, object, Any], Any] Validation function. Returns ------- ``validator`` """ cls._registry_validators[key] = fvalidate return fvalidate return register
# ------------------------------------------- def __repr__(self): return f"<Parameter {self._attr_name!r} at {hex(id(self))}>"
# =================================================================== # Built-in validators @Parameter.register_validator("default") def _validate_with_unit(cosmology, param, value): """ Default Parameter value validator. Adds/converts units if Parameter has a unit. """ if param.unit is not None: with u.add_enabled_equivalencies(param.equivalencies): value = u.Quantity(value, param.unit) return value @Parameter.register_validator("float") def _validate_to_float(cosmology, param, value): """Parameter value validator with units, and converted to float.""" value = _validate_with_unit(cosmology, param, value) return float(value) @Parameter.register_validator("scalar") def _validate_to_scalar(cosmology, param, value): """""" value = _validate_with_unit(cosmology, param, value) if not value.isscalar: raise ValueError(f"{param.name} is a non-scalar quantity") return value @Parameter.register_validator("non-negative") def _validate_non_negative(cosmology, param, value): """Parameter value validator where value is a positive float.""" value = _validate_to_float(cosmology, param, value) if value < 0.0: raise ValueError(f"{param.name} cannot be negative.") return value