Source code for astropy.coordinates.attributes

# -*- coding: utf-8 -*-
# Licensed under a 3-clause BSD style license - see LICENSE.rst


# Dependencies
import numpy as np

# Project
from astropy import units as u
from astropy.utils import OrderedDescriptor, ShapedLikeNDArray

__all__ = ['Attribute', 'TimeAttribute', 'QuantityAttribute',
           'EarthLocationAttribute', 'CoordinateAttribute',
           'CartesianRepresentationAttribute',
           'DifferentialAttribute']


[docs]class Attribute(OrderedDescriptor): """A non-mutable data descriptor to hold a frame attribute. This class must be used to define frame attributes (e.g. ``equinox`` or ``obstime``) that are included in a frame class definition. Examples -------- The `~astropy.coordinates.FK4` class uses the following class attributes:: class FK4(BaseCoordinateFrame): equinox = TimeAttribute(default=_EQUINOX_B1950) obstime = TimeAttribute(default=None, secondary_attribute='equinox') This means that ``equinox`` and ``obstime`` are available to be set as keyword arguments when creating an ``FK4`` class instance and are then accessible as instance attributes. The instance value for the attribute must be stored in ``'_' + <attribute_name>`` by the frame ``__init__`` method. Note in this example that ``equinox`` and ``obstime`` are time attributes and use the ``TimeAttributeFrame`` class. This subclass overrides the ``convert_input`` method to validate and convert inputs into a ``Time`` object. Parameters ---------- default : object Default value for the attribute if not provided secondary_attribute : str Name of a secondary instance attribute which supplies the value if ``default is None`` and no value was supplied during initialization. """ _class_attribute_ = 'frame_attributes' _name_attribute_ = 'name' name = '<unbound>' def __init__(self, default=None, secondary_attribute=''): self.default = default self.secondary_attribute = secondary_attribute super().__init__()
[docs] def convert_input(self, value): """ Validate the input ``value`` and convert to expected attribute class. The base method here does nothing, but subclasses can implement this as needed. The method should catch any internal exceptions and raise ValueError with an informative message. The method returns the validated input along with a boolean that indicates whether the input value was actually converted. If the input value was already the correct type then the ``converted`` return value should be ``False``. Parameters ---------- value : object Input value to be converted. Returns ------- output_value The ``value`` converted to the correct type (or just ``value`` if ``converted`` is False) converted : bool True if the conversion was actually performed, False otherwise. Raises ------ ValueError If the input is not valid for this attribute. """ return value, False
def __get__(self, instance, frame_cls=None): if instance is None: out = self.default else: out = getattr(instance, '_' + self.name, self.default) if out is None: out = getattr(instance, self.secondary_attribute, self.default) out, converted = self.convert_input(out) if instance is not None: instance_shape = getattr(instance, 'shape', None) if instance_shape is not None and (getattr(out, 'size', 1) > 1 and out.shape != instance_shape): # If the shapes do not match, try broadcasting. try: if isinstance(out, ShapedLikeNDArray): out = out._apply(np.broadcast_to, shape=instance_shape, subok=True) else: out = np.broadcast_to(out, instance_shape, subok=True) except ValueError: # raise more informative exception. raise ValueError( "attribute {} should be scalar or have shape {}, " "but is has shape {} and could not be broadcast." .format(self.name, instance_shape, out.shape)) converted = True if converted: setattr(instance, '_' + self.name, out) return out def __set__(self, instance, val): raise AttributeError('Cannot set frame attribute')
[docs]class TimeAttribute(Attribute): """ Frame attribute descriptor for quantities that are Time objects. See the `~astropy.coordinates.Attribute` API doc for further information. Parameters ---------- default : object Default value for the attribute if not provided secondary_attribute : str Name of a secondary instance attribute which supplies the value if ``default is None`` and no value was supplied during initialization. """
[docs] def convert_input(self, value): """ Convert input value to a Time object and validate by running through the Time constructor. Also check that the input was a scalar. 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. """ from astropy.time import Time if value is None: return None, False if isinstance(value, Time): out = value converted = False else: try: out = Time(value) except Exception as err: raise ValueError( 'Invalid time input {}={!r}\n{}'.format(self.name, value, err)) converted = True # Set attribute as read-only for arrays (not allowed by numpy # for array scalars) if out.shape: out.writeable = False return out, converted
[docs]class CartesianRepresentationAttribute(Attribute): """ A frame attribute that is a CartesianRepresentation with specified units. Parameters ---------- default : object Default value for the attribute if not provided 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 """ def __init__(self, default=None, secondary_attribute='', unit=None): super().__init__(default, secondary_attribute) self.unit = unit
[docs] def convert_input(self, value): """ Checks that the input is a CartesianRepresentation with the correct unit, or the special value ``[0, 0, 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. """ if (isinstance(value, list) and len(value) == 3 and all(v == 0 for v in value) and self.unit is not None): return CartesianRepresentation(np.zeros(3) * self.unit), True else: # is it a CartesianRepresentation with correct unit? if hasattr(value, 'xyz') and value.xyz.unit == self.unit: return value, False converted = True # if it's a CartesianRepresentation, get the xyz Quantity value = getattr(value, 'xyz', value) if not hasattr(value, 'unit'): raise TypeError('tried to set a {} with something that does ' 'not have a unit.' .format(self.__class__.__name__)) value = value.to(self.unit) # now try and make a CartesianRepresentation. cartrep = CartesianRepresentation(value, copy=False) return cartrep, converted
[docs]class QuantityAttribute(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 """ def __init__(self, default=None, secondary_attribute='', unit=None, shape=None): if default is None and unit is None: raise ValueError('Either a default quantity value must be ' 'provided, or a unit must be provided to define a ' 'QuantityAttribute.') if default is not None and unit is None: unit = default.unit self.unit = unit self.shape = shape default = self.convert_input(default)[0] super().__init__(default, secondary_attribute)
[docs] def convert_input(self, 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. """ if value is None: return None, False if np.all(value == 0) and self.unit is not None: return u.Quantity(np.zeros(self.shape), self.unit), True else: if not hasattr(value, 'unit') and self.unit != u.dimensionless_unscaled: raise TypeError('Tried to set a QuantityAttribute with ' 'something that does not have a unit.') oldvalue = value value = u.Quantity(oldvalue, self.unit, copy=False) if self.shape is not None and value.shape != self.shape: raise ValueError('The provided value has shape "{}", but ' 'should have shape "{}"'.format(value.shape, self.shape)) converted = oldvalue is not value return value, converted
[docs]class EarthLocationAttribute(Attribute): """ A frame attribute that can act as a `~astropy.coordinates.EarthLocation`. It can be created as anything that can be transformed to the `~astropy.coordinates.ITRS` frame, but always presents as an `EarthLocation` when accessed after creation. Parameters ---------- default : object Default value for the attribute if not provided secondary_attribute : str Name of a secondary instance attribute which supplies the value if ``default is None`` and no value was supplied during initialization. """
[docs] def convert_input(self, 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. """ if value is None: return None, False elif isinstance(value, EarthLocation): return value, False else: # we have to do the import here because of some tricky circular deps from .builtin_frames import ITRS if not hasattr(value, 'transform_to'): raise ValueError('"{}" was passed into an ' 'EarthLocationAttribute, but it does not have ' '"transform_to" method'.format(value)) itrsobj = value.transform_to(ITRS) return itrsobj.earth_location, True
[docs]class CoordinateAttribute(Attribute): """ A frame attribute which is a coordinate object. It can be given as a low-level frame class *or* a `~astropy.coordinates.SkyCoord`, but will always be converted to the low-level frame class when accessed. Parameters ---------- frame : a coordinate frame class The type of frame this attribute can be default : object Default value for the attribute if not provided secondary_attribute : str Name of a secondary instance attribute which supplies the value if ``default is None`` and no value was supplied during initialization. """ def __init__(self, frame, default=None, secondary_attribute=''): self._frame = frame super().__init__(default, secondary_attribute)
[docs] def convert_input(self, value): """ Checks that the input is a SkyCoord with the necessary units (or the special value ``None``). 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. """ if value is None: return None, False elif isinstance(value, self._frame): return value, False else: if not hasattr(value, 'transform_to'): raise ValueError('"{}" was passed into a ' 'CoordinateAttribute, but it does not have ' '"transform_to" method'.format(value)) transformedobj = value.transform_to(self._frame) if hasattr(transformedobj, 'frame'): transformedobj = transformedobj.frame return transformedobj, True
[docs]class DifferentialAttribute(Attribute): """A frame attribute which is a differential instance. The optional ``allowed_classes`` argument allows specifying a restricted set of valid differential classes to check the input against. Otherwise, any `~astropy.coordinates.BaseDifferential` subclass instance is valid. Parameters ---------- default : object Default value for the attribute if not provided allowed_classes : tuple, optional A list of allowed differential classes for this attribute to have. secondary_attribute : str Name of a secondary instance attribute which supplies the value if ``default is None`` and no value was supplied during initialization. """ def __init__(self, default=None, allowed_classes=None, secondary_attribute=''): if allowed_classes is not None: self.allowed_classes = tuple(allowed_classes) else: self.allowed_classes = BaseDifferential super().__init__(default, secondary_attribute)
[docs] def convert_input(self, value): """ Checks that the input is a differential object and is one of the allowed class types. Parameters ---------- value : object Input value. 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. """ if value is None: return None, False if not isinstance(value, self.allowed_classes): if len(self.allowed_classes) == 1: value = self.allowed_classes[0](value) else: raise TypeError('Tried to set a DifferentialAttribute with ' 'an unsupported Differential type {}. Allowed ' 'classes are: {}' .format(value.__class__, self.allowed_classes)) return value, True
# do this here to prevent a series of complicated circular imports from .earth import EarthLocation from .representation import CartesianRepresentation, BaseDifferential