QuantityAttribute

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

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:

default : value 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_attribute : str

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

unit : unit object or None

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

shape : tuple 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)

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

Parameters:

value : object

Input value to be converted.

Returns:

out, converted : correctly-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.