QuantityAttribute¶

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

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

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

Methods Documentation

convert_input(self, value)[source]¶

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

Parameters

Returns

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

Raises