v2.2.7

CHANGELOG.md

 # v2.2.7
 
-* _TBA_
+* added inheritance from `abc` to Immutable
 
 # v2.2.6
 

docs/coding/structures.rst

@@ -63,11 +63,13 @@ Immutable
 =========
 
 Make your classes immutable. Normal assignment is only supported in the constructor,
-anywhere else it's a TypeError
+anywhere else it's a TypeError.
+
+Immutable inherits from abc.ABCMeta, so it's safe to use abstract base classes here.
 
 ::
 
-    class Test(Immutable):
+    class Test(Immutable, metaclass=ABCMeta):
 
         attr: str = None
 

satella/__init__.py

 # coding=UTF-8
-__version__ = '2.2.7a1'
+__version__ = '2.2.7'

satella/coding/structures/immutable.py

+from abc import ABCMeta
+
 __all__ = ['Immutable']
 
 
-class ImmutableMetaType(type):
+class ImmutableMetaType(ABCMeta):
     def __call__(cls, *args, **kwargs):
         p = type.__call__(cls, *args, **kwargs)
-        p.__class__ = LockedImmutable
+        p.__dict__['_Immutable__locked_for_writes'] = True
         return p
 
 
@@ -19,14 +21,17 @@ class Immutable(metaclass=ImmutableMetaType):
     >>>         self.attribute = 'value'
     """
 
-
-class LockedImmutable(Immutable):
-
-    __doc__ = Immutable.__doc__
+    __locked_for_writes: bool = False
 
     # Following make this class immutable
     def __setattr__(self, attr, value):
-        raise TypeError('%s does not support attribute assignment' % (self.__class__.__qualname__,))
+        if self.__locked_for_writes:
+            raise TypeError('%s does not support attribute assignment' % (self.__class__.__qualname__,))
+        else:
+            super().__setattr__(attr, value)
 
     def __delattr__(self, attr):
-        raise TypeError('%s does not support attribute deletion' % (self.__class__.__qualname__,))
+        if self.__locked_for_writes:
+            raise TypeError('%s does not support attribute deletion' % (self.__class__.__qualname__,))
+        else:
+            super().__delattr__(attr)

tests/test_coding/test_structures.py

 import copy
+import abc
 import unittest
 
 import mock
@@ -152,13 +153,7 @@ class TestHeap(unittest.TestCase):
 
 
 class TestImmutable(unittest.TestCase):
-    def test_immutable(self):
-        class Point2D(Immutable):
-            def __init__(self, x: float, y: float):
-                self.x = x
-                self.y = y
-
-        a = Point2D(2.5, 2)
+    def _test_an_instance(self, a):
         self.assertEqual(a.x, 2.5)
         self.assertEqual(a.y, 2)
 
@@ -171,3 +166,30 @@ class TestImmutable(unittest.TestCase):
             del a.x
 
         self.assertRaises(TypeError, delete_x)
+
+    def test_immutable(self):
+        class Point2D(Immutable):
+            def __init__(self, x: float, y: float):
+                self.x = x
+                self.y = y
+
+        self._test_an_instance(Point2D(2.5, 2))
+
+    def test_immutable_abc(self):
+        class Point2D(abc.ABC, Immutable):
+            def __init__(self, x: float, y: float):
+                self.x = x
+                self.y = y
+
+        self._test_an_instance(Point2D(2.5, 2))
+
+    def test_advanced_inheritance_hierarchy(self):
+        class BaseClass(abc.ABC):
+            pass
+
+        class Point2D(BaseClass, Immutable):
+            def __init__(self, x: float, y: float):
+                self.x = x
+                self.y = y
+
+        self._test_an_instance(Point2D(2.5, 2))