Issue #22609: Constructors and update methods of mapping classes in the

collections module now accept the self keyword argument.

Lib/_collections_abc.py

@@ -592,14 +592,15 @@ class MutableMapping(Mapping):
             If E present and lacks .keys() method, does:     for (k, v) in E: D[k] = v
             In either case, this is followed by: for k, v in F.items(): D[k] = v
         '''
-        if len(args) > 2:
+        if not args:
-            raise TypeError("update() takes at most 2 positional "
+            raise TypeError("descriptor 'update' of 'MutableMapping' object "
-                            "arguments ({} given)".format(len(args)))
+                            "needs an argument")
-        elif not args:
+        self, *args = args
-            raise TypeError("update() takes at least 1 argument (0 given)")
+        if len(args) > 1:
-        self = args[0]
+            raise TypeError('update expected at most 1 arguments, got %d' %
-        other = args[1] if len(args) >= 2 else ()
+                            len(args))
-
+        if args:
+            other = args[0]
             if isinstance(other, Mapping):
                 for key in other:
                     self[key] = other[key]

Lib/collections/__init__.py

@@ -55,12 +55,16 @@ class OrderedDict(dict):
     # Individual links are kept alive by the hard reference in self.__map.
     # Those hard references disappear when a key is deleted from an OrderedDict.
 
-    def __init__(self, *args, **kwds):
+    def __init__(*args, **kwds):
         '''Initialize an ordered dictionary.  The signature is the same as
         regular dictionaries, but keyword arguments are not recommended because
         their insertion order is arbitrary.
 
         '''
+        if not args:
+            raise TypeError("descriptor '__init__' of 'OrderedDict' object "
+                            "needs an argument")
+        self, *args = args
         if len(args) > 1:
             raise TypeError('expected at most 1 arguments, got %d' % len(args))
         try:
@@ -479,7 +483,7 @@ class Counter(dict):
     #   http://code.activestate.com/recipes/259174/
     #   Knuth, TAOCP Vol. II section 4.6.3
 
-    def __init__(self, iterable=None, **kwds):
+    def __init__(*args, **kwds):
         '''Create a new, empty Counter object.  And if given, count elements
         from an input iterable.  Or, initialize the count from another mapping
         of elements to their counts.
@@ -490,8 +494,14 @@ class Counter(dict):
         >>> c = Counter(a=4, b=2)                   # a new counter from keyword args
 
         '''
-        super().__init__()
+        if not args:
-        self.update(iterable, **kwds)
+            raise TypeError("descriptor '__init__' of 'Counter' object "
+                            "needs an argument")
+        self, *args = args
+        if len(args) > 1:
+            raise TypeError('expected at most 1 arguments, got %d' % len(args))
+        super(Counter, self).__init__()
+        self.update(*args, **kwds)
 
     def __missing__(self, key):
         'The count of elements not in the Counter is zero.'
@@ -542,7 +552,7 @@ class Counter(dict):
         raise NotImplementedError(
             'Counter.fromkeys() is undefined.  Use Counter(iterable) instead.')
 
-    def update(self, iterable=None, **kwds):
+    def update(*args, **kwds):
         '''Like dict.update() but add counts instead of replacing them.
 
         Source can be an iterable, a dictionary, or another Counter instance.
@@ -562,6 +572,13 @@ class Counter(dict):
         # contexts.  Instead, we implement straight-addition.  Both the inputs
         # and outputs are allowed to contain zero and negative counts.
 
+        if not args:
+            raise TypeError("descriptor 'update' of 'Counter' object "
+                            "needs an argument")
+        self, *args = args
+        if len(args) > 1:
+            raise TypeError('expected at most 1 arguments, got %d' % len(args))
+        iterable = args[0] if args else None
         if iterable is not None:
             if isinstance(iterable, Mapping):
                 if self:
@@ -569,13 +586,13 @@ class Counter(dict):
                     for elem, count in iterable.items():
                         self[elem] = count + self_get(elem, 0)
                 else:
-                    super().update(iterable) # fast path when counter is empty
+                    super(Counter, self).update(iterable) # fast path when counter is empty
             else:
                 _count_elements(self, iterable)
         if kwds:
             self.update(kwds)
 
-    def subtract(self, iterable=None, **kwds):
+    def subtract(*args, **kwds):
         '''Like dict.update() but subtracts counts instead of replacing them.
         Counts can be reduced below zero.  Both the inputs and outputs are
         allowed to contain zero and negative counts.
@@ -591,6 +608,13 @@ class Counter(dict):
         -1
 
         '''
+        if not args:
+            raise TypeError("descriptor 'subtract' of 'Counter' object "
+                            "needs an argument")
+        self, *args = args
+        if len(args) > 1:
+            raise TypeError('expected at most 1 arguments, got %d' % len(args))
+        iterable = args[0] if args else None
         if iterable is not None:
             self_get = self.get
             if isinstance(iterable, Mapping):
@@ -898,7 +922,14 @@ class ChainMap(MutableMapping):
 class UserDict(MutableMapping):
 
     # Start by filling-out the abstract methods
-    def __init__(self, dict=None, **kwargs):
+    def __init__(*args, **kwargs):
+        if not args:
+            raise TypeError("descriptor '__init__' of 'UserDict' object "
+                            "needs an argument")
+        self, *args = args
+        if len(args) > 1:
+            raise TypeError('expected at most 1 arguments, got %d' % len(args))
+        dict = args[0] if args else None
         self.data = {}
         if dict is not None:
             self.update(dict)

Lib/test/test_collections.py

@@ -1137,6 +1137,28 @@ class TestCounter(unittest.TestCase):
         self.assertEqual(c.setdefault('e', 5), 5)
         self.assertEqual(c['e'], 5)
 
+    def test_init(self):
+        self.assertEqual(list(Counter(self=42).items()), [('self', 42)])
+        self.assertEqual(list(Counter(iterable=42).items()), [('iterable', 42)])
+        self.assertEqual(list(Counter(iterable=None).items()), [('iterable', None)])
+        self.assertRaises(TypeError, Counter, 42)
+        self.assertRaises(TypeError, Counter, (), ())
+        self.assertRaises(TypeError, Counter.__init__)
+
+    def test_update(self):
+        c = Counter()
+        c.update(self=42)
+        self.assertEqual(list(c.items()), [('self', 42)])
+        c = Counter()
+        c.update(iterable=42)
+        self.assertEqual(list(c.items()), [('iterable', 42)])
+        c = Counter()
+        c.update(iterable=None)
+        self.assertEqual(list(c.items()), [('iterable', None)])
+        self.assertRaises(TypeError, Counter().update, 42)
+        self.assertRaises(TypeError, Counter().update, {}, {})
+        self.assertRaises(TypeError, Counter.update)
+
     def test_copying(self):
         # Check that counters are copyable, deepcopyable, picklable, and
         #have a repr/eval round-trip
@@ -1258,6 +1280,16 @@ class TestCounter(unittest.TestCase):
         c.subtract('aaaabbcce')
         self.assertEqual(c, Counter(a=-1, b=0, c=-1, d=1, e=-1))
 
+        c = Counter()
+        c.subtract(self=42)
+        self.assertEqual(list(c.items()), [('self', -42)])
+        c = Counter()
+        c.subtract(iterable=42)
+        self.assertEqual(list(c.items()), [('iterable', -42)])
+        self.assertRaises(TypeError, Counter().subtract, 42)
+        self.assertRaises(TypeError, Counter().subtract, {}, {})
+        self.assertRaises(TypeError, Counter.subtract)
+
     def test_unary(self):
         c = Counter(a=-5, b=0, c=5, d=10, e=15,g=40)
         self.assertEqual(dict(+c), dict(c=5, d=10, e=15, g=40))
@@ -1308,8 +1340,11 @@ class TestOrderedDict(unittest.TestCase):
                                           c=3, e=5).items()), pairs)                # mixed input
 
         # make sure no positional args conflict with possible kwdargs
-        self.assertEqual(inspect.getargspec(OrderedDict.__dict__['__init__']).args,
+        self.assertEqual(list(OrderedDict(self=42).items()), [('self', 42)])
-                         ['self'])
+        self.assertEqual(list(OrderedDict(other=42).items()), [('other', 42)])
+        self.assertRaises(TypeError, OrderedDict, 42)
+        self.assertRaises(TypeError, OrderedDict, (), ())
+        self.assertRaises(TypeError, OrderedDict.__init__)
 
         # Make sure that direct calls to __init__ do not clear previous contents
         d = OrderedDict([('a', 1), ('b', 2), ('c', 3), ('d', 44), ('e', 55)])
@@ -1354,6 +1389,10 @@ class TestOrderedDict(unittest.TestCase):
         self.assertEqual(list(d.items()),
             [('a', 1), ('b', 2), ('c', 3), ('d', 4), ('e', 5), ('f', 6), ('g', 7)])
 
+        self.assertRaises(TypeError, OrderedDict().update, 42)
+        self.assertRaises(TypeError, OrderedDict().update, (), ())
+        self.assertRaises(TypeError, OrderedDict.update)
+
     def test_abc(self):
         self.assertIsInstance(OrderedDict(), MutableMapping)
         self.assertTrue(issubclass(OrderedDict, MutableMapping))
@@ -1600,6 +1639,24 @@ class SubclassMappingTests(mapping_tests.BasicTestMappingProtocol):
         d = self._empty_mapping()
         self.assertRaises(KeyError, d.popitem)
 
+class TestUserDict(unittest.TestCase):
+
+    def test_init(self):
+        self.assertEqual(list(UserDict(self=42).items()), [('self', 42)])
+        self.assertEqual(list(UserDict(dict=42).items()), [('dict', 42)])
+        self.assertEqual(list(UserDict(dict=None).items()), [('dict', None)])
+        self.assertRaises(TypeError, UserDict, 42)
+        self.assertRaises(TypeError, UserDict, (), ())
+        self.assertRaises(TypeError, UserDict.__init__)
+
+    def test_update(self):
+        d = UserDict()
+        d.update(self=42)
+        self.assertEqual(list(d.items()), [('self', 42)])
+        self.assertRaises(TypeError, UserDict().update, 42)
+        self.assertRaises(TypeError, UserDict().update, {}, {})
+        self.assertRaises(TypeError, UserDict.update)
+
 
 ################################################################################
 ### Run tests
@@ -1611,7 +1668,8 @@ def test_main(verbose=None):
     NamedTupleDocs = doctest.DocTestSuite(module=collections)
     test_classes = [TestNamedTuple, NamedTupleDocs, TestOneTrickPonyABCs,
                     TestCollectionABCs, TestCounter, TestChainMap,
-                    TestOrderedDict, GeneralMappingTests, SubclassMappingTests]
+                    TestOrderedDict, GeneralMappingTests, SubclassMappingTests,
+                    TestUserDict,]
     support.run_unittest(*test_classes)
     support.run_doctest(collections, verbose)
 

Misc/NEWS

@@ -191,6 +191,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #22609: Constructors and update methods of mapping classes in the
+  collections module now accept the self keyword argument.
+
 - Issue #22940: Add readline.append_history_file.
 
 - Issue #19676: Added the "namereplace" error handler.