# CoordinateTransform¶

class astropy.coordinates.CoordinateTransform(fromsys, tosys, priority=1, register_graph=None)[source]

Bases: object

An object that transforms a coordinate from one system to another. Subclasses must implement __call__ with the provided signature. They should also call this superclass’s __init__ in their __init__.

Parameters
fromsysclass

The coordinate frame class to start from.

tosysclass

The coordinate frame class to transform into.

prioritynumber

The priority if this transform when finding the shortest coordinate transform path - large numbers are lower priorities.

register_graph

A graph to register this transformation with on creation, or None to leave it unregistered.

Methods Summary

 __call__(self, fromcoord, toframe) Does the actual coordinate transformation from the fromsys class to the tosys class. register(self, graph) Add this transformation to the requested Transformation graph, replacing anything already connecting these two coordinates. unregister(self, graph) Remove this transformation from the requested transformation graph.

Methods Documentation

abstract __call__(self, fromcoord, toframe)[source]

Does the actual coordinate transformation from the fromsys class to the tosys class.

Parameters
fromcoordfromsys object

An object of class matching fromsys that is to be transformed.

toframeobject

An object that has the attributes necessary to fully specify the frame. That is, it must have attributes with names that match the keys of the dictionary that tosys.get_frame_attr_names() returns. Typically this is of class tosys, but it might be some other class as long as it has the appropriate attributes.

Returns
tocoordtosys object

The new coordinate after the transform has been applied.

register(self, graph)[source]

Add this transformation to the requested Transformation graph, replacing anything already connecting these two coordinates.

Parameters
grapha TransformGraph object

The graph to register this transformation with.

unregister(self, graph)[source]

Remove this transformation from the requested transformation graph.

Parameters
grapha TransformGraph object

The graph to unregister this transformation from.

Raises
ValueError

If this is not currently in the transform graph.