QuantityAttribute#

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

Bases: 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:
defaultnumber or Quantity or None, optional

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, optional

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

unitastropy:unit-like or None, optional

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

shapetuple or None, optional

If given, specifies the shape the attribute must be

docstr

Description of the frame attribute for help and documentation

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, bool

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.