Parameter¶

class astropy.cosmology.Parameter(*, derived=False, unit=None, equivalencies=[], fvalidate='default', fmt='', doc=None)[source]¶

Cosmological parameter (descriptor).

Should only be used with a Cosmology subclass.

Parameters:

derivedbool (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 \(\Omega_{de,0}`\) as an independent parameter (\(\Omega_{de,0} \equiv 1 - \Omega_{tot}\)).
unitastropy:unit-like or None (optional, keyword-only): The Unit for the Parameter. If None (default) no unit as assumed.
equivalenciesEquivalency or sequence thereof: Unit equivalencies for this Parameter.
fvalidatecallable()[[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 validator().
fmtstr (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 since version 5.1.
docstr or None (optional, keyword-only): Parameter description.

Examples

For worked examples see FLRW.

Attributes Summary

`derived`	Whether the Parameter is derived; true parameters are not.
`equivalencies`	Equivalencies used when initializing Parameter.
`format_spec`	Deprecated since version 5.1.
`fvalidate`	Function to validate a potential value of this Parameter.
`name`	Parameter name.
`unit`	Parameter unit.

Methods Summary

`clone`(**kw)	Clone this `Parameter`, changing any constructor argument.
`register_validator`(key[, fvalidate])	Decorator to register a new kind of validator function.
`validate`(cosmology, value)	Run the validator on this Parameter.
`validator`(fvalidate)	Make new Parameter with custom `fvalidate`.

Attributes Documentation

format_spec¶: Deprecated since version 5.1: The format_spec attribute is deprecated and may be removed in a future version.

Methods Documentation

clone(**kw)[source]¶

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)

classmethod register_validator(key, fvalidate=None)[source]¶

Decorator to register a new kind of validator function.

Parameters:

keystr
fvalidatecallable()[[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.

validate(cosmology, value)[source]¶

Run the validator on this Parameter.

Parameters:

Returns:

Any: The output of calling fvalidate(cosmology, self, value) (yes, that parameter order).

validator(fvalidate)[source]¶

Make new Parameter with custom fvalidate.

Note: Parameter.fvalidator must be the top-most descriptor decorator.

Parameters:

Returns: