introduce Rprofs ABC

`RprofsInstant` (replacing the previous `Rprofs`) and `RprofsAveraged`
both implement this ABC instead of having the latter inherit from the
former.

Author: amorison

src/stagpy/stagyydata.py

@@ -230,15 +230,11 @@ class RprofsAveraged(step.Rprofs):
 
     The [`StepsView.rprofs_averaged`][stagpy.stagyydata.StepsView.rprofs_averaged]
     attribute is an instance of this class.
-
-    It implements the same interface as [`Rprofs`][stagpy.step.Rprofs] but
-    returns time-averaged profiles instead.
     """
 
     def __init__(self, steps: StepsView):
         self.steps = steps.filter(rprofs=True)
         self._cached_data: dict[str, dt.Rprof] = {}
-        super().__init__(next(iter(self.steps)))
 
     def __getitem__(self, name: str) -> dt.Rprof:
         # the averaging method has two shortcomings:
@@ -259,9 +255,25 @@ def __getitem__(self, name: str) -> dt.Rprof:
 
     @property
     def stepstr(self) -> str:
-        """String representation of steps indices."""
         return self.steps.stepstr
 
+    @cached_property
+    def _first_rprofs(self) -> step.RprofsInstant:
+        first_step = next(iter(self.steps))
+        return first_step.rprofs
+
+    @property
+    def centers(self) -> NDArray:
+        return self._first_rprofs.centers
+
+    @property
+    def walls(self) -> NDArray:
+        return self._first_rprofs.walls
+
+    @property
+    def bounds(self) -> tuple[float, float]:
+        return self._first_rprofs.bounds
+
 
 @dataclass(frozen=True)
 class Steps:

src/stagpy/step.py

@@ -9,6 +9,7 @@
 from __future__ import annotations
 
 import typing
+from abc import ABC, abstractmethod
 from collections import abc
 from functools import cached_property
 from itertools import chain
@@ -449,16 +450,47 @@ def __iter__(self) -> NoReturn:
         raise TypeError("tracers collection is not iterable")
 
 
-class Rprofs:
-    """Radial profiles data structure.
-
-    The `Step.rprofs` attribute is an instance of this class.
+class Rprofs(ABC):
+    """Radial profiles.
 
     `Rprofs` implements the getitem mechanism.  Keys are profile names
     defined in `stagpy.phyvars.RPROF[_EXTRA]`.  Items are
     [`Rprof`][stagpy.datatypes.Rprof] instances.
     """
 
+    @abstractmethod
+    def __getitem__(self, name: str) -> Rprof: ...
+
+    @property
+    @abstractmethod
+    def stepstr(self) -> str:
+        """String representation of steps indices."""
+
+    @property
+    @abstractmethod
+    def centers(self) -> NDArray:
+        """Radial position of cell centers."""
+
+    @property
+    @abstractmethod
+    def walls(self) -> NDArray:
+        """Radial position of cell walls."""
+
+    @property
+    @abstractmethod
+    def bounds(self) -> tuple[float, float]:
+        """Radial or vertical position of boundaries.
+
+        Radial/vertical positions of boundaries of the domain.
+        """
+
+
+class RprofsInstant(Rprofs):
+    """Radial profiles at a given step.
+
+    The `Step.rprofs` attribute is an instance of this class.
+    """
+
     def __init__(self, step: Step):
         self.step = step
         self._cached_extra: dict[str, Rprof] = {}
@@ -595,7 +627,7 @@ def __init__(self, istep: int, sdat: StagyyData):
             self, phyvars.SFIELD, {}, phyvars.SFIELD_FILES, phyvars.SFIELD_FILES_H5
         )
         self.tracers = Tracers(self)
-        self.rprofs = Rprofs(self)
+        self.rprofs = RprofsInstant(self)
 
     def __repr__(self) -> str:
         if self.isnap is not None: