# Licensed under a 3-clause BSD style license - see LICENSE.rst
import copy
import astropy.units as u
from astropy.utils.decorators import deprecated_attribute, deprecated_renamed_argument
__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 https://docs.python.org/3/library/string.html#formatspec
.. deprecated:: 5.1
doc : str or None (optional, keyword-only)
Parameter description.
Examples
--------
For worked examples see :class:`~astropy.cosmology.FLRW`.
"""
_registry_validators = {}
@deprecated_renamed_argument("fmt", None, since="5.1")
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._format_spec = str(fmt) # deprecated.
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
format_spec = deprecated_attribute("format_spec", since="5.1")
@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
# Get from instance
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(f"can't set attribute {self._attr_name} again")
# 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
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,
"doc": self.__doc__}
# fmt will issue a deprecation warning if passed, so only passed if
# it's not the default.
if self._format_spec:
kw["fmt"] = self._format_spec
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', doc=None)
>>> p.clone(unit="km")
Parameter(derived=False, unit=Unit("km"), equivalencies=[],
fvalidate='default', 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 (self.name == other.name))
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"{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