Source code for astropy.cosmology.core

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

import abc
import functools
import inspect
from types import FunctionType, MappingProxyType

import numpy as np

import astropy.units as u
from astropy.io.registry import UnifiedReadWriteMethod
from astropy.utils.decorators import classproperty
from astropy.utils.metadata import MetaData

from .connect import CosmologyFromFormat, CosmologyRead, CosmologyToFormat, CosmologyWrite
from .parameter import Parameter

# Originally authored by Andrew Becker (becker@astro.washington.edu),
# and modified by Neil Crighton (neilcrighton@gmail.com), Roban Kramer
# (robanhk@gmail.com), and Nathaniel Starkman (n.starkman@mail.utoronto.ca).

# Many of these adapted from Hogg 1999, astro-ph/9905116
# and Linder 2003, PRL 90, 91301

__all__ = ["Cosmology", "CosmologyError", "FlatCosmologyMixin"]

__doctest_requires__ = {}  # needed until __getattr__ removed

# registry of cosmology classes with {key=name : value=class}
_COSMOLOGY_CLASSES = dict()


[docs]class CosmologyError(Exception): pass
[docs]class Cosmology(metaclass=abc.ABCMeta): """Base-class for all Cosmologies. Parameters ---------- *args Arguments into the cosmology; used by subclasses, not this base class. name : str or None (optional, keyword-only) The name of the cosmology. meta : dict or None (optional, keyword-only) Metadata for the cosmology, e.g., a reference. **kwargs Arguments into the cosmology; used by subclasses, not this base class. Notes ----- Class instances are static -- you cannot (and should not) change the values of the parameters. That is, all of the above attributes (except meta) are read only. For details on how to create performant custom subclasses, see the documentation on :ref:`astropy-cosmology-fast-integrals`. """ meta = MetaData() # Unified I/O object interchange methods from_format = UnifiedReadWriteMethod(CosmologyFromFormat) to_format = UnifiedReadWriteMethod(CosmologyToFormat) # Unified I/O read and write methods read = UnifiedReadWriteMethod(CosmologyRead) write = UnifiedReadWriteMethod(CosmologyWrite) # Parameters __parameters__ = () __all_parameters__ = () # --------------------------------------------------------------- def __init_subclass__(cls): super().__init_subclass__() # override signature of __new__ to match __init__ so IDEs and Sphinx # will display the correct signature new = FunctionType( # almost exact copy of __new__ cls.__new__.__code__, cls.__new__.__globals__, name=cls.__new__.__name__, argdefs=cls.__new__.__defaults__, closure=cls.__new__.__closure__) new = functools.update_wrapper(new, cls.__new__) # update further new.__kwdefaults__ = cls.__init__.__kwdefaults__ # fill in kwdefaults sig = cls._init_signature # override signature to look like init sig = sig.replace(parameters=[inspect.Parameter("cls", 0)] + list(sig.parameters.values())) new.__signature__ = sig # set __new__ with copied & modified version cls.__new__ = new # ------------------- # Parameters # Get parameters that are still Parameters, either in this class or above. parameters = [] derived_parameters = [] for n in cls.__parameters__: p = getattr(cls, n) if isinstance(p, Parameter): derived_parameters.append(n) if p.derived else parameters.append(n) # Add new parameter definitions for n, v in cls.__dict__.items(): if n in parameters or n.startswith("_") or not isinstance(v, Parameter): continue derived_parameters.append(n) if v.derived else parameters.append(n) # reorder to match signature ordered = [parameters.pop(parameters.index(n)) for n in cls._init_signature.parameters.keys() if n in parameters] parameters = ordered + parameters # place "unordered" at the end cls.__parameters__ = tuple(parameters) cls.__all_parameters__ = cls.__parameters__ + tuple(derived_parameters) # ------------------- # register as a Cosmology subclass _COSMOLOGY_CLASSES[cls.__qualname__] = cls @classproperty(lazy=True) def _init_signature(cls): """Initialization signature (without 'self').""" # get signature, dropping "self" by taking arguments [1:] sig = inspect.signature(cls.__init__) sig = sig.replace(parameters=list(sig.parameters.values())[1:]) return sig # --------------------------------------------------------------- def __new__(cls, *args, **kwargs): self = super().__new__(cls) # bundle and store initialization arguments on the instance ba = cls._init_signature.bind_partial(*args, **kwargs) ba.apply_defaults() # and fill in the defaults self._init_arguments = ba.arguments return self def __init__(self, name=None, meta=None): self._name = name self.meta.update(meta or {}) @property def name(self): """The name of the Cosmology instance.""" return self._name
[docs] def clone(self, *, meta=None, **kwargs): """Returns a copy of this object with updated parameters, as specified. This cannot be used to change the type of the cosmology, so ``clone()`` cannot be used to change between flat and non-flat cosmologies. Parameters ---------- meta : mapping or None (optional, keyword-only) Metadata that will update the current metadata. **kwargs Cosmology parameter (and name) modifications. If any parameter is changed and a new name is not given, the name will be set to "[old name] (modified)". Returns ------- newcosmo : `~astropy.cosmology.Cosmology` subclass instance A new instance of this class with updated parameters as specified. If no modifications are requested, then a reference to this object is returned instead of copy. Examples -------- To make a copy of the ``Planck13`` cosmology with a different matter density (``Om0``), and a new name: >>> from astropy.cosmology import Planck13 >>> newcosmo = Planck13.clone(name="Modified Planck 2013", Om0=0.35) If no name is specified, the new name will note the modification. >>> Planck13.clone(Om0=0.35).name 'Planck13 (modified)' """ # Quick return check, taking advantage of the Cosmology immutability. if meta is None and not kwargs: return self # There are changed parameter or metadata values. # The name needs to be changed accordingly, if it wasn't already. kwargs.setdefault("name", (self.name + " (modified)" if self.name is not None else None)) # mix new meta into existing, preferring the former. new_meta = {**self.meta, **(meta or {})} # Mix kwargs into initial arguments, preferring the former. new_init = {**self._init_arguments, "meta": new_meta, **kwargs} # Create BoundArgument to handle args versus kwargs. # This also handles all errors from mismatched arguments ba = self._init_signature.bind_partial(**new_init) # Return new instance, respecting args vs kwargs return self.__class__(*ba.args, **ba.kwargs)
# --------------------------------------------------------------- # comparison methods
[docs] def is_equivalent(self, other): r"""Check equivalence between Cosmologies. Two cosmologies may be equivalent even if not the same class. For example, an instance of ``LambdaCDM`` might have :math:`\Omega_0=1` and :math:`\Omega_k=0` and therefore be flat, like ``FlatLambdaCDM``. Parameters ---------- other : `~astropy.cosmology.Cosmology` subclass instance The object in which to compare. Returns ------- bool True if cosmologies are equivalent, False otherwise. """ # The options are: 1) same class & parameters; 2) same class, different # parameters; 3) different classes, equivalent parameters; 4) different # classes, different parameters. (1) & (3) => True, (2) & (4) => False. equiv = self.__equiv__(other) if equiv is NotImplemented and hasattr(other, "__equiv__"): equiv = other.__equiv__(self) # that failed, try from 'other' return equiv if equiv is not NotImplemented else False
def __equiv__(self, other): """Cosmology equivalence. Use ``.is_equivalent()`` for actual check! Parameters ---------- other : `~astropy.cosmology.Cosmology` subclass instance The object in which to compare. Returns ------- bool or `NotImplemented` `NotImplemented` if 'other' is from a different class. `True` if 'other' is of the same class and has matching parameters and parameter values. `False` otherwise. """ if other.__class__ is not self.__class__: return NotImplemented # allows other.__equiv__ # check all parameters in 'other' match those in 'self' and 'other' has # no extra parameters (latter part should never happen b/c same class) params_eq = (set(self.__all_parameters__) == set(other.__all_parameters__) and all(np.all(getattr(self, k) == getattr(other, k)) for k in self.__all_parameters__)) return params_eq def __eq__(self, other): """Check equality between Cosmologies. Checks the Parameters and immutable fields (i.e. not "meta"). Parameters ---------- other : `~astropy.cosmology.Cosmology` subclass instance The object in which to compare. Returns ------- bool True if Parameters and names are the same, False otherwise. """ if other.__class__ is not self.__class__: return NotImplemented # allows other.__eq__ # check all parameters in 'other' match those in 'self' equivalent = self.__equiv__(other) # non-Parameter checks: name name_eq = (self.name == other.name) return equivalent and name_eq # --------------------------------------------------------------- def __repr__(self): ps = {k: getattr(self, k) for k in self.__parameters__} # values cps = {k: getattr(self.__class__, k) for k in self.__parameters__} # Parameter objects namelead = f"{self.__class__.__qualname__}(" if self.name is not None: namelead += f"name=\"{self.name}\", " # nicely formatted parameters fmtps = (k + '=' + format(v, cps[k].format_spec if v is not None else '') for k, v in ps.items()) return namelead + ", ".join(fmtps) + ")" def __astropy_table__(self, cls, copy, **kwargs): """Return a `~astropy.table.Table` of type ``cls``. Parameters ---------- cls : type Astropy ``Table`` class or subclass. copy : bool Ignored. **kwargs : dict, optional Additional keyword arguments. Passed to ``self.to_format()``. See ``Cosmology.to_format.help("astropy.table")`` for allowed kwargs. Returns ------- `astropy.table.Table` or subclass instance Instance of type ``cls``. """ return self.to_format("astropy.table", cls=cls, **kwargs)
[docs]class FlatCosmologyMixin(metaclass=abc.ABCMeta): """ Mixin class for flat cosmologies. Do NOT instantiate directly. Note that all instances of ``FlatCosmologyMixin`` are flat, but not all flat cosmologies are instances of ``FlatCosmologyMixin``. As example, ``LambdaCDM`` **may** be flat (for the a specific set of parameter values), but ``FlatLambdaCDM`` **will** be flat. """ pass
# ----------------------------------------------------------------------------- def __getattr__(attr): from . import flrw if hasattr(flrw, attr): import warnings from astropy.utils.exceptions import AstropyDeprecationWarning warnings.warn( f"`astropy.cosmology.core.{attr}` has been moved (since v5.0) and " f"should be imported as ``from astropy.cosmology import {attr}``." " In future this will raise an exception.", AstropyDeprecationWarning ) return getattr(flrw, attr) raise AttributeError(f"module {__name__!r} has no attribute {attr!r}.")