QuantityAttribute

class astropy.coordinates.QuantityAttribute(default=None, secondary_attribute='', unit=None, shape=None)[source]

Bases: astropy.coordinates.Attribute

A frame attribute that is a quantity with specified units and shape (optionally).

Can be None, which should be used for special cases in associated frame transformations like “this quantity should be ignored” or similar.

Parameters
defaultvalue or Quantity or None

Default value for the attribute if the user does not supply one. If a Quantity, it must be consistent with unit, or if a value, unit cannot be None.

secondary_attributestr

Name of a secondary instance attribute which supplies the value if default is None and no value was supplied during initialization.

unitunit object or None

Name of a unit that the input will be converted into. If None, no unit-checking or conversion is performed

shapetuple or None

If given, specifies the shape the attribute must be

Methods Summary

convert_input(value)

Checks that the input is a Quantity with the necessary units (or the special value 0).

Methods Documentation

convert_input(value)[source]

Checks that the input is a Quantity with the necessary units (or the special value 0).

Parameters
valueobject

Input value to be converted.

Returns
out, convertedcorrectly-typed object, boolean

Tuple consisting of the correctly-typed object and a boolean which indicates if conversion was actually performed.

Raises
ValueError

If the input is not valid for this attribute.