Source code for astropy.cosmology.realizations

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

import sys
import warnings

from astropy import units as u
from astropy.utils.exceptions import AstropyDeprecationWarning
from astropy.utils.state import ScienceState

from . import parameters
from .core import _COSMOLOGY_CLASSES, Cosmology

__all__ = ["default_cosmology"] + list(parameters.available)

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


# Pre-defined cosmologies. This loops over the parameter sets in the
# parameters module and creates a corresponding cosmology instance
for key in parameters.available:
    params = dict(getattr(parameters, key))  # get parameters dict (copy)
    params.setdefault("name", key)
    # make cosmology
    cosmo = Cosmology.from_format(params, format="mapping", move_to_meta=True)
    cosmo.__doc__ = (f"{key} instance of {cosmo.__class__.__qualname__} "
                     f"cosmology\n(from {cosmo.meta['reference']})")
    # put in this namespace
    setattr(sys.modules[__name__], key, cosmo)

del key, params, cosmo  # clean the namespace

#########################################################################
# 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 """ _value = "Planck18"
[docs] @staticmethod def get_cosmology_from_string(arg): """ Return a cosmology instance from a string. """ if arg == "no_default": cosmo = None else: try: cosmo = getattr(sys.modules[__name__], arg) except AttributeError: s = "Unknown cosmology '{}'. Valid cosmologies:\n{}".format( arg, parameters.available ) raise ValueError(s) return cosmo
[docs] @classmethod def validate(cls, value): if value is None: value = "Planck18" if isinstance(value, str): if value == "Planck18_arXiv_v2": warnings.warn( f"{value} is deprecated in astropy 4.2, use Planck18 instead", AstropyDeprecationWarning, ) return cls.get_cosmology_from_string(value) elif isinstance(value, Cosmology): return value else: raise TypeError( "default_cosmology must be a string or Cosmology instance." )