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
import warnings
# Project
from astropy import units as u
from astropy.utils.exceptions import AstropyDeprecationWarning
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 {0} should be scalar or have shape {1}, "
"but is has shape {2} 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 {0}={1!r}\n{2}'.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 {0} 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).
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
shape : tuple or None
If given, specifies the shape the attribute must be
"""
def __init__(self, default=None, secondary_attribute='', unit=None, shape=None):
super().__init__(default, secondary_attribute)
self.unit = unit
self.shape = shape
[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 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 "{0}", but '
'should have shape "{1}"'.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('"{0}" 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('"{0}" 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 not isinstance(value, self.allowed_classes):
raise TypeError('Tried to set a DifferentialAttribute with '
'an unsupported Differential type {0}. Allowed '
'classes are: {1}'
.format(value.__class__,
self.allowed_classes))
return value, True
# Backwards-compatibility: these are the only classes that were previously
# released in v1.3
class FrameAttribute(Attribute):
def __init__(self, *args, **kwargs):
warnings.warn("FrameAttribute has been renamed to Attribute.",
AstropyDeprecationWarning)
super().__init__(*args, **kwargs)
[docs]class TimeFrameAttribute(TimeAttribute):
def __init__(self, *args, **kwargs):
warnings.warn("TimeFrameAttribute has been renamed to TimeAttribute.",
AstropyDeprecationWarning)
super().__init__(*args, **kwargs)
[docs]class QuantityFrameAttribute(QuantityAttribute):
def __init__(self, *args, **kwargs):
warnings.warn("QuantityFrameAttribute has been renamed to "
"QuantityAttribute.", AstropyDeprecationWarning)
super().__init__(*args, **kwargs)
[docs]class CartesianRepresentationFrameAttribute(CartesianRepresentationAttribute):
def __init__(self, *args, **kwargs):
warnings.warn("CartesianRepresentationFrameAttribute has been renamed "
"to CartesianRepresentationAttribute.",
AstropyDeprecationWarning)
super().__init__(*args, **kwargs)
# do this here to prevent a series of complicated circular imports
from .earth import EarthLocation
from .representation import CartesianRepresentation, BaseDifferential