Fixing #53. Following advice from @suvayu: class DataAccessor(object,…

… metaclass=RequiredAttributesMetaclass), i.e. DataAccessor inheriting from RequiredAttributesMetaclass is an overkill, since RequiredAttributesMetaclass does nothing more than checking for required attributes. requiredatts.py can be removed and DataAccessor can be turned into a dataclass, which will have the required arguments declared.

sourcefinder/accessors/dataaccessor.py

@@ -1,80 +1,80 @@
 import logging
-from math import degrees, sqrt, sin, pi, cos
 
-from sourcefinder.accessors.requiredatts import RequiredAttributesMetaclass
+import numpy
+from math import degrees, sqrt, sin, pi, cos
+from dataclasses import dataclass
+from sourcefinder.utility.coordinates import WCS
 
 logger = logging.getLogger(__name__)
 
 
-class DataAccessor(object, metaclass=RequiredAttributesMetaclass):
-    _required_attributes = [
-        'beam',
-        'centre_ra',
-        'centre_decl',
-        'data',
-        'freq_bw',
-        'freq_eff',
-        'pixelsize',
-        'tau_time',
-        'taustart_ts',
-        'url',
-        'wcs',
-    ]
-
-    def __init__(self):
-        # Sphinx only picks up the class docstring if it's under an __init__
-        # *le sigh*
-        """
-        Base class for accessors used with
-        :class:`sourcefinder.image.ImageData`.
-
-        Data accessors provide a uniform way for the ImageData class (ie,
-        generic image representation) to access the various ways in which
-        images may be stored (FITS files, arrays in memory, potentially HDF5,
-        etc).
-
-        This class cannot be instantiated directly, but should be subclassed
-        and the abstract properties provided. Note that all abstract
-        properties are required to provide a valid accessor.
-
-        Additional properties may also be provided by subclasses. However,
-        TraP components are required to degrade gracefully in the absence of
-        this optional properties.
-
-        The required attributes are as follows:
-
-        Attributes:
-            beam (tuple): Restoring beam. Tuple of three floats:
-                semi-major axis (in pixels), semi-minor axis (pixels)
-                and position angle (radians).
-            centre_ra (float): Right ascension at the central pixel of the image.
-                Units of J2000 decimal degrees.
-            centre_decl (float): Declination at the central pixel of the image.
-                Units of J2000 decimal degrees.
-            data(numpy.ndarray): Two dimensional numpy.ndarray of floating point
-                pixel values.
-                (TODO: Definitive statement on orientation/transposing.)
-            freq_bw(float): The frequency bandwidth of this image in Hz.
-            freq_eff(float): Effective frequency of the image in Hz.
-                That is, the mean frequency of all the visibility data which
-                comprises this image.
-            pixelsize(tuple): (x, y) tuple representing the size of a pixel
-                along each axis in units of degrees.
-            tau_time(float): Total time on sky in seconds.
-            taustart_ts(float): Timestamp of the first integration which
-                constitutes part of this image. MJD in seconds.
-            url(string): A (string) URL representing the location of the image
-                at time of processing.
-            wcs(:class:`sourcefinder.utility.coordinates.WCS`): An instance of
-                :py:class:`sourcefinder.utility.coordinates.WCS`,
-                describing the mapping from data pixels to sky-coordinates.
-
-        The class also provides some common functionality:
-        static methods used for parsing datafiles, and an 'extract_metadata'
-        function which provides key info in a simple dict format.
-        """
-
-    def extract_metadata(self):
+@dataclass
+class DataAccessor:
+    # Sphinx only picks up the class docstring if it's under an __init__
+    # *le sigh*
+    """
+    Base class for accessors used with
+    :class:`sourcefinder.image.ImageData`.
+
+    Data accessors provide a uniform way for the ImageData class (ie,
+    generic image representation) to access the various ways in which
+    images may be stored (FITS files, arrays in memory, potentially HDF5,
+    etc).
+
+    This class cannot be instantiated directly, but should be subclassed
+    and the abstract properties provided. Note that all abstract
+    properties are required to provide a valid accessor.
+
+    Additional properties may also be provided by subclasses. However,
+    TraP components are required to degrade gracefully in the absence of
+    this optional properties.
+
+    The required attributes are as follows:
+
+    Attributes:
+        beam (tuple): Restoring beam. Tuple of three floats:
+            semi-major axis (in pixels), semi-minor axis (pixels)
+            and position angle (radians).
+        centre_ra (float): Right ascension at the central pixel of the image.
+            Units of J2000 decimal degrees.
+        centre_decl (float): Declination at the central pixel of the image.
+            Units of J2000 decimal degrees.
+        data(numpy.ndarray): Two dimensional numpy.ndarray of floating point
+            pixel values.
+            (TODO: Definitive statement on orientation/transposing.)
+        freq_bw(float): The frequency bandwidth of this image in Hz.
+        freq_eff(float): Effective frequency of the image in Hz.
+            That is, the mean frequency of all the visibility data which
+            comprises this image.
+        pixelsize(tuple): (x, y) tuple representing the size of a pixel
+            along each axis in units of degrees.
+        tau_time(float): Total time on sky in seconds.
+        taustart_ts(float): Timestamp of the first integration which
+            constitutes part of this image. MJD in seconds.
+        url(string): A (string) URL representing the location of the image
+            at time of processing.
+        wcs(:class:`sourcefinder.utility.coordinates.WCS`): An instance of
+            :py:class:`sourcefinder.utility.coordinates.WCS`,
+            describing the mapping from data pixels to sky-coordinates.
+
+    The class also provides some common functionality:
+    static methods used for parsing datafiles, and an 'extract_metadata'
+    function which provides key info in a simple dict format.
+    """
+
+    beam: tuple
+    centre_ra: float
+    centre_decl: float
+    data: numpy.ndarray
+    freq_bw: float
+    freq_eff: float
+    pixelsize: tuple
+    tau_time: float
+    taustart_ts: float
+    url: str
+    wcs: WCS
+
+    def extract_metadata(self) -> dict:
         """
         Massage the class attributes into a flat dictionary with
         database-friendly values.
@@ -155,4 +155,4 @@ def degrees2pixels(bmaj, bmin, bpa, deltax, deltay):
             (sin(pi * bpa / 180.) ** 2) / (deltay ** 2))
         )
         theta = pi * bpa / 180
-        return (semimaj, semimin, theta)
+        return semimaj, semimin, theta