Source code for astropy.cosmology.realizations

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

# STDLIB
import pathlib
import sys
from typing import Optional, Union

# LOCAL
from astropy.utils.data import get_pkg_data_path
from astropy.utils.decorators import deprecated
from astropy.utils.state import ScienceState

from .core import Cosmology

_COSMOLOGY_DATA_DIR = pathlib.Path(get_pkg_data_path("cosmology", "data", package="astropy"))
available = tuple(sorted(p.stem for p in _COSMOLOGY_DATA_DIR.glob("*.ecsv")))


__all__ = ["available", "default_cosmology"] + list(available)

__doctest_requires__ = {"*": ["scipy"]}


def __getattr__(name):
    """Make specific realizations from data files with lazy import from
    `PEP 562 <https://www.python.org/dev/peps/pep-0562/>`_.

    Raises
    ------
    AttributeError
        If "name" is not in :mod:`astropy.cosmology.realizations`
    """
    if name not in available:
        raise AttributeError(f"module {__name__!r} has no attribute {name!r}.")

    cosmo = Cosmology.read(str(_COSMOLOGY_DATA_DIR / name) + ".ecsv", format="ascii.ecsv")
    cosmo.__doc__ = (f"{name} instance of {cosmo.__class__.__qualname__} "
                     f"cosmology\n(from {cosmo.meta['reference']})")

    # Cache in this module so `__getattr__` is only called once per `name`.
    setattr(sys.modules[__name__], name, cosmo)

    return cosmo


def __dir__():
    """Directory, including lazily-imported objects."""
    return __all__


#########################################################################
# The science state below contains the current cosmology.
#########################################################################


[docs]class default_cosmology(ScienceState): """The default cosmology to use. To change it:: >>> from astropy.cosmology import default_cosmology, WMAP7 >>> with default_cosmology.set(WMAP7): ... # WMAP7 cosmology in effect ... pass Or, you may use a string:: >>> with default_cosmology.set('WMAP7'): ... # WMAP7 cosmology in effect ... pass To get the default cosmology: >>> default_cosmology.get() FlatLambdaCDM(name="Planck18", H0=67.66 km / (Mpc s), Om0=0.30966, ... """ _default_value = "Planck18" _value = "Planck18"
[docs] @deprecated("5.0", alternative="get") @classmethod def get_cosmology_from_string(cls, arg): """Return a cosmology instance from a string.""" if arg == "no_default": value = None else: value = cls._get_from_registry(arg) return value
[docs] @classmethod def validate(cls, value: Union[Cosmology, str, None]) -> Optional[Cosmology]: """Return a Cosmology given a value. Parameters ---------- value : None, str, or `~astropy.cosmology.Cosmology` Returns ------- `~astropy.cosmology.Cosmology` instance Raises ------ TypeError If ``value`` is not a string or |Cosmology|. """ # None -> default if value is None: value = cls._default_value # Parse to Cosmology. Error if cannot. if isinstance(value, str): # special-case one string if value == "no_default": value = None else: value = cls._get_from_registry(value) elif not isinstance(value, Cosmology): raise TypeError("default_cosmology must be a string or Cosmology instance, " f"not {value}.") return value
@classmethod def _get_from_registry(cls, name: str) -> Cosmology: """Get a registered Cosmology realization. Parameters ---------- name : str The built-in |Cosmology| realization to retrieve. Returns ------- `astropy.cosmology.Cosmology` The cosmology realization of `name`. Raises ------ ValueError If ``name`` is a str, but not for a built-in Cosmology. TypeError If ``name`` is for a non-Cosmology object. """ try: value = getattr(sys.modules[__name__], name) except AttributeError: raise ValueError(f"Unknown cosmology {name!r}. " f"Valid cosmologies:\n{available}") if not isinstance(value, Cosmology): raise TypeError(f"cannot find a Cosmology realization called {name}.") return value