Fields

Custom Peewee field types used in astra’s database models (astra.fields). All standard field types (e.g. FloatField, IntegerField, TextField) include a GlossaryFieldMixin that automatically sets help_text from the glossary if not explicitly provided.

GlossaryFieldMixin

A mixin class applied to all astra field types. When a field is bound to a model, if no help_text has been set, it automatically looks up the field name in Glossary and uses the matching description.

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BitField

class BitField(*args, **kwargs)

A binary bit-field (extends Peewee’s BitField) that supports per-flag help_text. Defaults to 0. Each flag is a boolean descriptor on the model instance.

BitField.flag

def flag(value=None, help_text=None) -> FlagDescriptor

Register a new flag in the bit field.

Parameter	Type	Default	Description
value	int or None	None	The bit value. If None, auto-increments (1, 2, 4, 8, …).
help_text	str or None	None	Description of the flag. If None, looked up from the glossary using the attribute name.

Returns: A FlagDescriptor that acts as a boolean property on model instances.

Example:

from astra.fields import BitField

class MyModel(BaseModel):
    result_flags = BitField(default=0)
    flag_bad_fit = result_flags.flag(help_text="Fit did not converge")
    flag_low_snr = result_flags.flag(help_text="Signal-to-noise ratio below threshold")

# Usage:
instance = MyModel()
instance.flag_bad_fit = True
print(instance.flag_bad_fit)  # True

The FlagDescriptor also supports SQL expressions for queries:

MyModel.select().where(MyModel.flag_bad_fit)

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PixelArray

class PixelArray(
    ext=None,
    column_name=None,
    transform=None,
    accessor_class=PixelArrayAccessorFITS,
    help_text=None,
    accessor_kwargs=None,
    **kwargs
)

A virtual Peewee field for array data (e.g. spectra, wavelengths) stored outside the database in FITS, HDF5, or pickle files. The data is loaded lazily on first access.

Parameters:

Parameter	Type	Default	Description
ext	int, str, callable, or None	None	The FITS extension (or HDF5 dataset path). Can be a callable that takes the model instance and returns the extension.
column_name	str or None	None	Column name within the extension. If None, defaults to the field name.
transform	callable or None	None	A function to transform the data after loading. For FITS accessors it receives (data, image, instance).
accessor_class	class	PixelArrayAccessorFITS	The accessor class to use. Options: PixelArrayAccessorFITS, PixelArrayAccessorHDF, PickledPixelArrayAccessor, LogLambdaArrayAccessor.
help_text	str or None	None	Description of the field.
accessor_kwargs	dict or None	None	Extra keyword arguments passed to the accessor constructor.

Example:

from astra.fields import PixelArray, PixelArrayAccessorFITS

class BossVisitSpectrum(BaseModel):
    wavelength = PixelArray(ext=1, column_name="loglam", transform=lambda x, *_: 10**x)
    flux = PixelArray(ext=1, column_name="flux")
    ivar = PixelArray(ext=1, column_name="ivar")

# Data is loaded lazily:
spectrum = BossVisitSpectrum.get_by_id(1)
print(spectrum.flux)  # numpy array loaded from FITS on first access

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BasePixelArrayAccessor

class BasePixelArrayAccessor(model, field, name, ext, column_name, transform=None, help_text=None, **kwargs)

Base class for all pixel array accessors. Manages a per-instance __pixel_data__ cache dictionary. Subclasses implement __get__ to load data from their respective file formats.

Built-in accessor subclasses:

Class	Description
PixelArrayAccessorFITS	Loads arrays from FITS files using astropy.io.fits. Supports both image and column access.
PixelArrayAccessorHDF	Loads arrays from HDF5 files using h5py.
PickledPixelArrayAccessor	Loads arrays from Python pickle files.

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LogLambdaArrayAccessor

class LogLambdaArrayAccessor(model, field, name, ext, column_name, crval, cdelt, naxis, transform=None, help_text=None)

A pixel array accessor that generates a log-linear wavelength array from header parameters, rather than reading it from a file. The wavelength grid is computed as:

wavelength = 10 ** (crval + cdelt * np.arange(naxis))

Additional parameters (beyond BasePixelArrayAccessor):

Parameter	Type	Description
crval	float	Log10 of the reference wavelength.
cdelt	float	Log10 wavelength step per pixel.
naxis	int	Number of pixels.

Example:

from astra.fields import PixelArray, LogLambdaArrayAccessor

class ApogeeVisitSpectrum(BaseModel):
    wavelength = PixelArray(
        accessor_class=LogLambdaArrayAccessor,
        accessor_kwargs=dict(crval=4.179, cdelt=6e-6, naxis=8575)
    )