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

collections module now accept the self keyword argument.

Lib/_abcoll.py

@@ -548,23 +548,25 @@ 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:
-            raise TypeError("update() takes at most 2 positional "
-                            "arguments ({} given)".format(len(args)))
-        elif not args:
-            raise TypeError("update() takes at least 1 argument (0 given)")
+        if not args:
+            raise TypeError("descriptor 'update' of 'MutableMapping' object "
+                            "needs an argument")
         self = args[0]
-        other = args[1] if len(args) >= 2 else ()
-
-        if isinstance(other, Mapping):
-            for key in other:
-                self[key] = other[key]
-        elif hasattr(other, "keys"):
-            for key in other.keys():
-                self[key] = other[key]
-        else:
-            for key, value in other:
-                self[key] = value
+        args = args[1:]
+        if len(args) > 1:
+            raise TypeError('update expected at most 1 arguments, got %d' %
+                            len(args))
+        if args:
+            other = args[0]
+            if isinstance(other, Mapping):
+                for key in other:
+                    self[key] = other[key]
+            elif hasattr(other, "keys"):
+                for key in other.keys():
+                    self[key] = other[key]
+            else:
+                for key, value in other:
+                    self[key] = value
         for key, value in kwds.items():
             self[key] = value
 

Lib/collections.py

@@ -35,12 +35,17 @@ class OrderedDict(dict):
     # The sentinel element never gets deleted (this simplifies the algorithm).
     # Each link is stored as a list of length three:  [PREV, NEXT, KEY].
 
-    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[0]
+        args = args[1:]
         if len(args) > 1:
             raise TypeError('expected at most 1 arguments, got %d' % len(args))
         try:
@@ -438,7 +443,7 @@ 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.
@@ -449,8 +454,15 @@ class Counter(dict):
         >>> c = Counter(a=4, b=2)                   # a new counter from keyword args
 
         '''
+        if not args:
+            raise TypeError("descriptor '__init__' of 'Counter' object "
+                            "needs an argument")
+        self = args[0]
+        args = args[1:]
+        if len(args) > 1:
+            raise TypeError('expected at most 1 arguments, got %d' % len(args))
         super(Counter, self).__init__()
-        self.update(iterable, **kwds)
+        self.update(*args, **kwds)
 
     def __missing__(self, key):
         'The count of elements not in the Counter is zero.'
@@ -501,7 +513,7 @@ 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.
@@ -521,6 +533,14 @@ 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[0]
+        args = args[1:]
+        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:
@@ -536,7 +556,7 @@ class Counter(dict):
         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.
@@ -552,6 +572,14 @@ class Counter(dict):
         -1
 
         '''
+        if not args:
+            raise TypeError("descriptor 'subtract' of 'Counter' object "
+                            "needs an argument")
+        self = args[0]
+        args = args[1:]
+        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):

Lib/test/test_collections.py

@@ -905,6 +905,28 @@ 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
@@ -1006,6 +1028,16 @@ 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)
+
 class TestOrderedDict(unittest.TestCase):
 
     def test_init(self):
@@ -1019,8 +1051,11 @@ 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'])
+        self.assertEqual(list(OrderedDict(self=42).items()), [('self', 42)])
+        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)])
@@ -1065,6 +1100,10 @@ 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))

Misc/NEWS

@@ -13,6 +13,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #22609: Constructors and update methods of mapping classes in the
+  collections module now accept the self keyword argument.
+
 
 What's New in Python 2.7.9 release candidate 1?
 ===============================================