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."
)