Add ABC ByteString which unifies bytes and bytearray (but not memoryview).

gvanrossum · gvanrossum · commit d05eb0043e59 · 2007-11-21T22:26:24.000Z
There's no ABC for "PEP 3118 style buffer API objects" because there's no
way to recognize these in Python (apart from trying to use memoryview()
on them).
Note that array.array really should be registered as a MutableSequence
but that would require importing it whenever collections is imported.
diff --git a/Lib/_abcoll.py b/Lib/_abcoll.py
@@ -16,6 +16,7 @@
            "Mapping", "MutableMapping",
            "MappingView", "KeysView", "ItemsView", "ValuesView",
            "Sequence", "MutableSequence",
+           "ByteString",
            ]
 
 ### ONE-TRICK PONIES ###
@@ -489,8 +490,17 @@ def count(self, value):
 
 Sequence.register(tuple)
 Sequence.register(str)
-Sequence.register(bytes)
-Sequence.register(memoryview)
+
+
+class ByteString(Sequence):
+
+    """This unifies bytes and bytearray.
+
+    XXX Should add all their methods.
+    """
+
+ByteString.register(bytes)
+ByteString.register(bytearray)
 
 
 class MutableSequence(Sequence):
@@ -531,4 +541,4 @@ def __iadd__(self, values):
         self.extend(values)
 
 MutableSequence.register(list)
-MutableSequence.register(bytes)
+MutableSequence.register(bytearray)  # Multiply inheriting, see ByteString
diff --git a/Lib/test/test_collections.py b/Lib/test/test_collections.py
@@ -8,6 +8,7 @@
 from collections import Set, MutableSet
 from collections import Mapping, MutableMapping
 from collections import Sequence, MutableSequence
+from collections import ByteString
 
 
 class TestNamedTuple(unittest.TestCase):
@@ -260,11 +261,21 @@ def test_Sequence(self):
             self.failUnless(issubclass(sample, Sequence))
         self.failUnless(issubclass(str, Sequence))
 
+    def test_ByteString(self):
+        for sample in [bytes, bytearray]:
+            self.failUnless(isinstance(sample(), ByteString))
+            self.failUnless(issubclass(sample, ByteString))
+        for sample in [str, list, tuple]:
+            self.failIf(isinstance(sample(), ByteString))
+            self.failIf(issubclass(sample, ByteString))
+        self.failIf(isinstance(memoryview(b""), ByteString))
+        self.failIf(issubclass(memoryview, ByteString))
+
     def test_MutableSequence(self):
-        for sample in [tuple, str]:
+        for sample in [tuple, str, bytes]:
             self.failIf(isinstance(sample(), MutableSequence))
             self.failIf(issubclass(sample, MutableSequence))
-        for sample in [list, bytes]:
+        for sample in [list, bytearray]:
             self.failUnless(isinstance(sample(), MutableSequence))
             self.failUnless(issubclass(sample, MutableSequence))
         self.failIf(issubclass(str, MutableSequence))
