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 ---------- 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`. fmt : str (optional, keyword-only) `format` specification, used when making string representation of the containing Cosmology. See doc : str or None (optional, keyword-only) Parameter description. Examples -------- For worked examples see :class:`~astropy.cosmology.FLRW`. """ _registry_validators = {} def __init__(self, *, derived=False, unit=None, equivalencies=[], fvalidate="default", fmt="", doc=None): # attribute name on container cosmology class. # really set in __set_name__, but if Parameter is not init'ed as a # descriptor this ensures that the attributes exist. self._attr_name = self._attr_name_private = None self._derived = derived self._fmt = str(fmt) # @property is `format_spec` self.__doc__ = doc # units stuff self._unit = u.Unit(unit) if unit is not None else None self._equivalencies = equivalencies # Parse registered `fvalidate` self._fvalidate_in = fvalidate # Always store input 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._fvalidate = fvalidate def __set_name__(self, cosmo_cls, name): # attribute name on container cosmology class 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``. """ 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] @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 _get_init_arguments(self, processed=False): """Initialization arguments. Parameters ---------- processed : bool Whether to more closely reproduce the input arguments (`False`, default) or the processed arguments (`True`). The former is better for string representations and round-tripping with ``eval(repr())``. Returns ------- dict[str, Any] """ # The keys are added in this order because `repr` prints them in order. kw = {"derived": self.derived, "unit": self.unit, "equivalencies": self.equivalencies, # Validator is always turned into a function, but for ``repr`` it's nice # to know if it was originally a string. "fvalidate": self.fvalidate if processed else self._fvalidate_in, "fmt": self.format_spec, "doc": self.__doc__} return kw
[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', fmt='', doc=None) >>> p.clone(unit="km") Parameter(derived=False, unit=Unit("km"), equivalencies=[], fvalidate='default', fmt='', doc=None) """ # Start with defaults, update from kw. kwargs = {**self._get_init_arguments(), **kw} # All initialization failures, like incorrect input are handled by init cloned = type(self)(**kwargs) # Transfer over the __set_name__ stuff. If `clone` is used to make a # new descriptor, __set_name__ will be called again, overwriting this. cloned._attr_name = self._attr_name cloned._attr_name_private = self._attr_name_private return cloned
def __eq__(self, other): """Check Parameter equality. Only equal to other Parameter objects. Returns ------- NotImplemented or True `True` if equal, `NotImplemented` otherwise. This allows `other` to be check for equality with ``other.__eq__``. Examples -------- >>> p1, p2 = Parameter(unit="km"), Parameter(unit="km") >>> p1 == p2 True >>> p3 = Parameter(unit="km / s") >>> p3 == p1 False >>> p1 != 2 True """ if not isinstance(other, Parameter): return NotImplemented # Check equality on all `_init_arguments` & `name`. # Need to compare the processed arguments because the inputs are many- # to-one, e.g. `fvalidate` can be a string or the equivalent function. return ((self._get_init_arguments(True) == other._get_init_arguments(True)) and ( == def __repr__(self): """String representation. ``eval(repr())`` should work, depending if contents like ``fvalidate`` can be similarly round-tripped. """ return "Parameter({})".format(", ".join(f"{k}={v!r}" for k, v in self._get_init_arguments().items()))
# =================================================================== # 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"{} 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"{} cannot be negative.") return value