import collections
import collections.abc
import gc
import pickle
import random
import re
import string
import sys
import unittest
import weakref
from test import support
from test.support import import_helper


class CustomHash:
    def __init__(self, hash):
        self.hash = hash
    def __hash__(self):
        return self.hash
    def __repr__(self):
        return f'<CustomHash {self.hash} at {id(self):#x}>'


class DictTest(unittest.TestCase):

    def test_invalid_keyword_arguments(self):
        class Custom(dict):
            pass
        for invalid in {1 : 2}, Custom({1 : 2}):
            with self.assertRaises(TypeError):
                dict(**invalid)
            with self.assertRaises(TypeError):
                {}.update(**invalid)

    def test_constructor(self):
        # calling built-in types without argument must return empty
        self.assertEqual(dict(), {})
        self.assertIsNot(dict(), {})

    def test_literal_constructor(self):
        # check literal constructor for different sized dicts
        # (to exercise the BUILD_MAP oparg).
        for n in (0, 1, 6, 256, 400):
            items = [(''.join(random.sample(string.ascii_letters, 8)), i)
                     for i in range(n)]
            random.shuffle(items)
            formatted_items = ('{!r}: {:d}'.format(k, v) for k, v in items)
            dictliteral = '{' + ', '.join(formatted_items) + '}'
            self.assertEqual(eval(dictliteral), dict(items))

    def test_merge_operator(self):

        a = {0: 0, 1: 1, 2: 1}
        b = {1: 1, 2: 2, 3: 3}

        c = a.copy()
        c |= b

        self.assertEqual(a | b, {0: 0, 1: 1, 2: 2, 3: 3})
        self.assertEqual(c, {0: 0, 1: 1, 2: 2, 3: 3})

        c = b.copy()
        c |= a

        self.assertEqual(b | a, {1: 1, 2: 1, 3: 3, 0: 0})
        self.assertEqual(c, {1: 1, 2: 1, 3: 3, 0: 0})

        c = a.copy()
        c |= [(1, 1), (2, 2), (3, 3)]

        self.assertEqual(c, {0: 0, 1: 1, 2: 2, 3: 3})

        self.assertIs(a.__or__(None), NotImplemented)
        self.assertIs(a.__or__(()), NotImplemented)
        self.assertIs(a.__or__("BAD"), NotImplemented)
        self.assertIs(a.__or__(""), NotImplemented)

        self.assertRaises(TypeError, a.__ior__, None)
        self.assertEqual(a.__ior__(()), {0: 0, 1: 1, 2: 1})
        self.assertRaises(ValueError, a.__ior__, "BAD")
        self.assertEqual(a.__ior__(""), {0: 0, 1: 1, 2: 1})

    def test_bool(self):
        self.assertIs(not {}, True)
        self.assertTrue({1: 2})
        self.assertIs(bool({}), False)
        self.assertIs(bool({1: 2}), True)

    def test_keys(self):
        d = {}
        self.assertEqual(set(d.keys()), set())
        d = {'a': 1, 'b': 2}
        k = d.keys()
        self.assertEqual(set(k), {'a', 'b'})
        self.assertIn('a', k)
        self.assertIn('b', k)
        self.assertIn('a', d)
        self.assertIn('b', d)
        self.assertRaises(TypeError, d.keys, None)
        self.assertEqual(repr(dict(a=1).keys()), "dict_keys(['a'])")

    def test_values(self):
        d = {}
        self.assertEqual(set(d.values()), set())
        d = {1:2}
        self.assertEqual(set(d.values()), {2})
        self.assertRaises(TypeError, d.values, None)
        self.assertEqual(repr(dict(a=1).values()), "dict_values([1])")

    def test_items(self):
        d = {}
        self.assertEqual(set(d.items()), set())

        d = {1:2}
        self.assertEqual(set(d.items()), {(1, 2)})
        self.assertRaises(TypeError, d.items, None)
        self.assertEqual(repr(dict(a=1).items()), "dict_items([('a', 1)])")

    def test_views_mapping(self):
        mappingproxy = type(type.__dict__)
        class Dict(dict):
            pass
        for cls in [dict, Dict]:
            d = cls()
            m1 = d.keys().mapping
            m2 = d.values().mapping
            m3 = d.items().mapping

            for m in [m1, m2, m3]:
                self.assertIsInstance(m, mappingproxy)
                self.assertEqual(m, d)

            d["foo"] = "bar"

            for m in [m1, m2, m3]:
                self.assertIsInstance(m, mappingproxy)
                self.assertEqual(m, d)

    def test_contains(self):
        d = {}
        self.assertNotIn('a', d)
        self.assertFalse('a' in d)
        self.assertTrue('a' not in d)
        d = {'a': 1, 'b': 2}
        self.assertIn('a', d)
        self.assertIn('b', d)
        self.assertNotIn('c', d)

        self.assertRaises(TypeError, d.__contains__)

    def test_len(self):
        d = {}
        self.assertEqual(len(d), 0)
        d = {'a': 1, 'b': 2}
        self.assertEqual(len(d), 2)

    def test_getitem(self):
        d = {'a': 1, 'b': 2}
        self.assertEqual(d['a'], 1)
        self.assertEqual(d['b'], 2)
        d['c'] = 3
        d['a'] = 4
        self.assertEqual(d['c'], 3)
        self.assertEqual(d['a'], 4)
        del d['b']
        self.assertEqual(d, {'a': 4, 'c': 3})

        self.assertRaises(TypeError, d.__getitem__)

        class BadEq(object):
            def __eq__(self, other):
                raise Exc()
            def __hash__(self):
                return 24

        d = {}
        d[BadEq()] = 42
        self.assertRaises(KeyError, d.__getitem__, 23)

        class Exc(Exception): pass

        class BadHash(object):
            fail = False
            def __hash__(self):
                if self.fail:
                    raise Exc()
                else:
                    return 42

        x = BadHash()
        d[x] = 42
        x.fail = True
        self.assertRaises(Exc, d.__getitem__, x)

    def test_clear(self):
        d = {1:1, 2:2, 3:3}
        d.clear()
        self.assertEqual(d, {})

        self.assertRaises(TypeError, d.clear, None)

    def test_update(self):
        d = {}
        d.update({1:100})
        d.update({2:20})
        d.update({1:1, 2:2, 3:3})
        self.assertEqual(d, {1:1, 2:2, 3:3})

        d.update()
        self.assertEqual(d, {1:1, 2:2, 3:3})

        self.assertRaises((TypeError, AttributeError), d.update, None)

        class SimpleUserDict:
            def __init__(self):
                self.d = {1:1, 2:2, 3:3}
            def keys(self):
                return self.d.keys()
            def __getitem__(self, i):
                return self.d[i]
        d.clear()
        d.update(SimpleUserDict())
        self.assertEqual(d, {1:1, 2:2, 3:3})

        class Exc(Exception): pass

        d.clear()
        class FailingUserDict:
            def keys(self):
                raise Exc
        self.assertRaises(Exc, d.update, FailingUserDict())

        class FailingUserDict:
            def keys(self):
                class BogonIter:
                    def __init__(self):
                        self.i = 1
                    def __iter__(self):
                        return self
                    def __next__(self):
                        if self.i:
                            self.i = 0
                            return 'a'
                        raise Exc
                return BogonIter()
            def __getitem__(self, key):
                return key
        self.assertRaises(Exc, d.update, FailingUserDict())

        class FailingUserDict:
            def keys(self):
                class BogonIter:
                    def __init__(self):
                        self.i = ord('a')
                    def __iter__(self):
                        return self
                    def __next__(self):
                        if self.i <= ord('z'):
                            rtn = chr(self.i)
                            self.i += 1
                            return rtn
                        raise StopIteration
                return BogonIter()
            def __getitem__(self, key):
                raise Exc
        self.assertRaises(Exc, d.update, FailingUserDict())

        class badseq(object):
            def __iter__(self):
                return self
            def __next__(self):
                raise Exc()

        self.assertRaises(Exc, {}.update, badseq())

        self.assertRaises(ValueError, {}.update, [(1, 2, 3)])

    def test_update_type_error(self):
        with self.assertRaises(TypeError) as cm:
            {}.update([object() for _ in range(3)])

        self.assertEqual(str(cm.exception), "object is not iterable")
        self.assertEqual(
            cm.exception.__notes__,
            ['Cannot convert dictionary update sequence element #0 to a sequence'],
        )

        def badgen():
            yield "key"
            raise TypeError("oops")
            yield "value"

        with self.assertRaises(TypeError) as cm:
            dict([badgen() for _ in range(3)])

        self.assertEqual(str(cm.exception), "oops")
        self.assertEqual(
            cm.exception.__notes__,
            ['Cannot convert dictionary update sequence element #0 to a sequence'],
        )

    def test_update_shared_keys(self):
        class MyClass: pass

        # Subclass str to enable us to create an object during the
        # dict.update() call.
        class MyStr(str):
            def __hash__(self):
                return super().__hash__()

            def __eq__(self, other):
                # Create an object that shares the same PyDictKeysObject as
                # obj.__dict__.
                obj2 = MyClass()
                obj2.a = "a"
                obj2.b = "b"
                obj2.c = "c"
                return super().__eq__(other)

        obj = MyClass()
        obj.a = "a"
        obj.b = "b"

        x = {}
        x[MyStr("a")] = MyStr("a")

        # gh-132617: this previously raised "dict mutated during update" error
        x.update(obj.__dict__)

        self.assertEqual(x, {
            MyStr("a"): "a",
            "b": "b",
        })

    def test_fromkeys(self):
        self.assertEqual(dict.fromkeys('abc'), {'a':None, 'b':None, 'c':None})
        d = {}
        self.assertIsNot(d.fromkeys('abc'), d)
        self.assertEqual(d.fromkeys('abc'), {'a':None, 'b':None, 'c':None})
        self.assertEqual(d.fromkeys((4,5),0), {4:0, 5:0})
        self.assertEqual(d.fromkeys([]), {})
        def g():
            yield 1
        self.assertEqual(d.fromkeys(g()), {1:None})
        self.assertRaises(TypeError, {}.fromkeys, 3)
        class dictlike(dict): pass
        self.assertEqual(dictlike.fromkeys('a'), {'a':None})
        self.assertEqual(dictlike().fromkeys('a'), {'a':None})
        self.assertIsInstance(dictlike.fromkeys('a'), dictlike)
        self.assertIsInstance(dictlike().fromkeys('a'), dictlike)
        class mydict(dict):
            def __new__(cls):
                return collections.UserDict()
        ud = mydict.fromkeys('ab')
        self.assertEqual(ud, {'a':None, 'b':None})
        self.assertIsInstance(ud, collections.UserDict)
        self.assertRaises(TypeError, dict.fromkeys)

        class Exc(Exception): pass

        class baddict1(dict):
            def __init__(self):
                raise Exc()

        self.assertRaises(Exc, baddict1.fromkeys, [1])

        class BadSeq(object):
            def __iter__(self):
                return self
            def __next__(self):
                raise Exc()

        self.assertRaises(Exc, dict.fromkeys, BadSeq())

        class baddict2(dict):
            def __setitem__(self, key, value):
                raise Exc()

        self.assertRaises(Exc, baddict2.fromkeys, [1])

        # test fast path for dictionary inputs
        res = dict(zip(range(6), [0]*6))
        d = dict(zip(range(6), range(6)))
        self.assertEqual(dict.fromkeys(d, 0), res)
        # test fast path for set inputs
        d = set(range(6))
        self.assertEqual(dict.fromkeys(d, 0), res)
        # test slow path for other iterable inputs
        d = list(range(6))
        self.assertEqual(dict.fromkeys(d, 0), res)

        # test fast path when object's constructor returns large non-empty dict
        class baddict3(dict):
            def __new__(cls):
                return d
        d = {i : i for i in range(1000)}
        res = d.copy()
        res.update(a=None, b=None, c=None)
        self.assertEqual(baddict3.fromkeys({"a", "b", "c"}), res)

        # test slow path when object is a proper subclass of dict
        class baddict4(dict):
            def __init__(self):
                dict.__init__(self, d)
        d = {i : i for i in range(1000)}
        res = d.copy()
        res.update(a=None, b=None, c=None)
        self.assertEqual(baddict4.fromkeys({"a", "b", "c"}), res)

    def test_copy(self):
        d = {1: 1, 2: 2, 3: 3}
        self.assertIsNot(d.copy(), d)
        self.assertEqual(d.copy(), d)
        self.assertEqual(d.copy(), {1: 1, 2: 2, 3: 3})

        copy = d.copy()
        d[4] = 4
        self.assertNotEqual(copy, d)

        self.assertEqual({}.copy(), {})
        self.assertRaises(TypeError, d.copy, None)

    def test_copy_fuzz(self):
        for dict_size in [10, 100, 1000, 10000, 100000]:
            dict_size = random.randrange(
                dict_size // 2, dict_size + dict_size // 2)
            with self.subTest(dict_size=dict_size):
                d = {}
                for i in range(dict_size):
                    d[i] = i

                d2 = d.copy()
                self.assertIsNot(d2, d)
                self.assertEqual(d, d2)
                d2['key'] = 'value'
                self.assertNotEqual(d, d2)
                self.assertEqual(len(d2), len(d) + 1)

    def test_copy_maintains_tracking(self):
        class A:
            pass

        key = A()

        for d in ({}, {'a': 1}, {key: 'val'}):
            d2 = d.copy()
            self.assertEqual(gc.is_tracked(d), gc.is_tracked(d2))

    def test_copy_noncompact(self):
        # Dicts don't compact themselves on del/pop operations.
        # Copy will use a slow merging strategy that produces
        # a compacted copy when roughly 33% of dict is a non-used
        # keys-space (to optimize memory footprint).
        # In this test we want to hit the slow/compacting
        # branch of dict.copy() and make sure it works OK.
        d = {k: k for k in range(1000)}
        for k in range(950):
            del d[k]
        d2 = d.copy()
        self.assertEqual(d2, d)

    def test_get(self):
        d = {}
        self.assertIs(d.get('c'), None)
        self.assertEqual(d.get('c', 3), 3)
        d = {'a': 1, 'b': 2}
        self.assertIs(d.get('c'), None)
        self.assertEqual(d.get('c', 3), 3)
        self.assertEqual(d.get('a'), 1)
        self.assertEqual(d.get('a', 3), 1)
        self.assertRaises(TypeError, d.get)
        self.assertRaises(TypeError, d.get, None, None, None)

    def test_setdefault(self):
        # dict.setdefault()
        d = {}
        self.assertIs(d.setdefault('key0'), None)
        d.setdefault('key0', [])
        self.assertIs(d.setdefault('key0'), None)
        d.setdefault('key', []).append(3)
        self.assertEqual(d['key'][0], 3)
        d.setdefault('key', []).append(4)
        self.assertEqual(len(d['key']), 2)
        self.assertRaises(TypeError, d.setdefault)

        class Exc(Exception): pass

        class BadHash(object):
            fail = False
            def __hash__(self):
                if self.fail:
                    raise Exc()
                else:
                    return 42

        x = BadHash()
        d[x] = 42
        x.fail = True
        self.assertRaises(Exc, d.setdefault, x, [])

    def test_setdefault_atomic(self):
        # Issue #13521: setdefault() calls __hash__ and __eq__ only once.
        class Hashed(object):
            def __init__(self):
                self.hash_count = 0
                self.eq_count = 0
            def __hash__(self):
                self.hash_count += 1
                return 42
            def __eq__(self, other):
                self.eq_count += 1
                return id(self) == id(other)
        hashed1 = Hashed()
        y = {hashed1: 5}
        hashed2 = Hashed()
        y.setdefault(hashed2, [])
        self.assertEqual(hashed1.hash_count, 1)
        self.assertEqual(hashed2.hash_count, 1)
        self.assertEqual(hashed1.eq_count + hashed2.eq_count, 1)

    def test_setitem_atomic_at_resize(self):
        class Hashed(object):
            def __init__(self):
                self.hash_count = 0
                self.eq_count = 0
            def __hash__(self):
                self.hash_count += 1
                return 42
            def __eq__(self, other):
                self.eq_count += 1
                return id(self) == id(other)
        hashed1 = Hashed()
        # 5 items
        y = {hashed1: 5, 0: 0, 1: 1, 2: 2, 3: 3}
        hashed2 = Hashed()
        # 6th item forces a resize
        y[hashed2] = []
        self.assertEqual(hashed1.hash_count, 1)
        self.assertEqual(hashed2.hash_count, 1)
        self.assertEqual(hashed1.eq_count + hashed2.eq_count, 1)

    def test_popitem(self):
        # dict.popitem()
        for copymode in -1, +1:
            # -1: b has same structure as a
            # +1: b is a.copy()
            for log2size in range(12):
                size = 2**log2size
                a = {}
                b = {}
                for i in range(size):
                    a[repr(i)] = i
                    if copymode < 0:
                        b[repr(i)] = i
                if copymode > 0:
                    b = a.copy()
                for i in range(size):
                    ka, va = ta = a.popitem()
                    self.assertEqual(va, int(ka))
                    kb, vb = tb = b.popitem()
                    self.assertEqual(vb, int(kb))
                    self.assertFalse(copymode < 0 and ta != tb)
                self.assertFalse(a)
                self.assertFalse(b)

        d = {}
        self.assertRaises(KeyError, d.popitem)

    def test_pop(self):
        # Tests for pop with specified key
        d = {}
        k, v = 'abc', 'def'
        d[k] = v
        self.assertRaises(KeyError, d.pop, 'ghi')

        self.assertEqual(d.pop(k), v)
        self.assertEqual(len(d), 0)

        self.assertRaises(KeyError, d.pop, k)

        self.assertEqual(d.pop(k, v), v)
        d[k] = v
        self.assertEqual(d.pop(k, 1), v)

        self.assertRaises(TypeError, d.pop)

        class Exc(Exception): pass

        class BadHash(object):
            fail = False
            def __hash__(self):
                if self.fail:
                    raise Exc()
                else:
                    return 42

        x = BadHash()
        d[x] = 42
        x.fail = True
        self.assertRaises(Exc, d.pop, x)

    def test_mutating_iteration(self):
        # changing dict size during iteration
        d = {}
        d[1] = 1
        with self.assertRaises(RuntimeError):
            for i in d:
                d[i+1] = 1

    def test_mutating_iteration_delete(self):
        # change dict content during iteration
        d = {}
        d[0] = 0
        with self.assertRaises(RuntimeError):
            for i in d:
                del d[0]
                d[0] = 0

    def test_mutating_iteration_delete_over_values(self):
        # change dict content during iteration
        d = {}
        d[0] = 0
        with self.assertRaises(RuntimeError):
            for i in d.values():
                del d[0]
                d[0] = 0

    def test_mutating_iteration_delete_over_items(self):
        # change dict content during iteration
        d = {}
        d[0] = 0
        with self.assertRaises(RuntimeError):
            for i in d.items():
                del d[0]
                d[0] = 0

    def test_mutating_lookup(self):
        # changing dict during a lookup (issue #14417)
        class NastyKey:
            mutate_dict = None

            def __init__(self, value):
                self.value = value

            def __hash__(self):
                # hash collision!
                return 1

            def __eq__(self, other):
                if NastyKey.mutate_dict:
                    mydict, key = NastyKey.mutate_dict
                    NastyKey.mutate_dict = None
                    del mydict[key]
                return self.value == other.value

        key1 = NastyKey(1)
        key2 = NastyKey(2)
        d = {key1: 1}
        NastyKey.mutate_dict = (d, key1)
        d[key2] = 2
        self.assertEqual(d, {key2: 2})

    def test_repr(self):
        d = {}
        self.assertEqual(repr(d), '{}')
        d[1] = 2
        self.assertEqual(repr(d), '{1: 2}')
        d = {}
        d[1] = d
        self.assertEqual(repr(d), '{1: {...}}')

        class Exc(Exception): pass

        class BadRepr(object):
            def __repr__(self):
                raise Exc()

        d = {1: BadRepr()}
        self.assertRaises(Exc, repr, d)

    @support.skip_wasi_stack_overflow()
    @support.skip_emscripten_stack_overflow()
    def test_repr_deep(self):
        d = {}
        for i in range(support.exceeds_recursion_limit()):
            d = {1: d}
        self.assertRaises(RecursionError, repr, d)

    def test_eq(self):
        self.assertEqual({}, {})
        self.assertEqual({1: 2}, {1: 2})

        class Exc(Exception): pass

        class BadCmp(object):
            def __eq__(self, other):
                raise Exc()
            def __hash__(self):
                return 1

        d1 = {BadCmp(): 1}
        d2 = {1: 1}

        with self.assertRaises(Exc):
            d1 == d2

    def test_keys_contained(self):
        self.helper_keys_contained(lambda x: x.keys())
        self.helper_keys_contained(lambda x: x.items())

    def helper_keys_contained(self, fn):
        # Test rich comparisons against dict key views, which should behave the
        # same as sets.
        empty = fn(dict())
        empty2 = fn(dict())
        smaller = fn({1:1, 2:2})
        larger = fn({1:1, 2:2, 3:3})
        larger2 = fn({1:1, 2:2, 3:3})
        larger3 = fn({4:1, 2:2, 3:3})

        self.assertTrue(smaller <  larger)
        self.assertTrue(smaller <= larger)
        self.assertTrue(larger >  smaller)
        self.assertTrue(larger >= smaller)

        self.assertFalse(smaller >= larger)
        self.assertFalse(smaller >  larger)
        self.assertFalse(larger  <= smaller)
        self.assertFalse(larger  <  smaller)

        self.assertFalse(smaller <  larger3)
        self.assertFalse(smaller <= larger3)
        self.assertFalse(larger3 >  smaller)
        self.assertFalse(larger3 >= smaller)

        # Inequality strictness
        self.assertTrue(larger2 >= larger)
        self.assertTrue(larger2 <= larger)
        self.assertFalse(larger2 > larger)
        self.assertFalse(larger2 < larger)

        self.assertTrue(larger == larger2)
        self.assertTrue(smaller != larger)

        # There is an optimization on the zero-element case.
        self.assertTrue(empty == empty2)
        self.assertFalse(empty != empty2)
        self.assertFalse(empty == smaller)
        self.assertTrue(empty != smaller)

        # With the same size, an elementwise compare happens
        self.assertTrue(larger != larger3)
        self.assertFalse(larger == larger3)

    def test_errors_in_view_containment_check(self):
        class C:
            def __eq__(self, other):
                raise RuntimeError

        d1 = {1: C()}
        d2 = {1: C()}
        with self.assertRaises(RuntimeError):
            d1.items() == d2.items()
        with self.assertRaises(RuntimeError):
            d1.items() != d2.items()
        with self.assertRaises(RuntimeError):
            d1.items() <= d2.items()
        with self.assertRaises(RuntimeError):
            d1.items() >= d2.items()

        d3 = {1: C(), 2: C()}
        with self.assertRaises(RuntimeError):
            d2.items() < d3.items()
        with self.assertRaises(RuntimeError):
            d3.items() > d2.items()

    def test_dictview_set_operations_on_keys(self):
        k1 = {1:1, 2:2}.keys()
        k2 = {1:1, 2:2, 3:3}.keys()
        k3 = {4:4}.keys()

        self.assertEqual(k1 - k2, set())
        self.assertEqual(k1 - k3, {1,2})
        self.assertEqual(k2 - k1, {3})
        self.assertEqual(k3 - k1, {4})
        self.assertEqual(k1 & k2, {1,2})
        self.assertEqual(k1 & k3, set())
        self.assertEqual(k1 | k2, {1,2,3})
        self.assertEqual(k1 ^ k2, {3})
        self.assertEqual(k1 ^ k3, {1,2,4})

    def test_dictview_set_operations_on_items(self):
        k1 = {1:1, 2:2}.items()
        k2 = {1:1, 2:2, 3:3}.items()
        k3 = {4:4}.items()

        self.assertEqual(k1 - k2, set())
        self.assertEqual(k1 - k3, {(1,1), (2,2)})
        self.assertEqual(k2 - k1, {(3,3)})
        self.assertEqual(k3 - k1, {(4,4)})
        self.assertEqual(k1 & k2, {(1,1), (2,2)})
        self.assertEqual(k1 & k3, set())
        self.assertEqual(k1 | k2, {(1,1), (2,2), (3,3)})
        self.assertEqual(k1 ^ k2, {(3,3)})
        self.assertEqual(k1 ^ k3, {(1,1), (2,2), (4,4)})

    def test_items_symmetric_difference(self):
        rr = random.randrange
        for _ in range(100):
            left = {x:rr(3) for x in range(20) if rr(2)}
            right = {x:rr(3) for x in range(20) if rr(2)}
            with self.subTest(left=left, right=right):
                expected = set(left.items()) ^ set(right.items())
                actual = left.items() ^ right.items()
                self.assertEqual(actual, expected)

    def test_dictview_mixed_set_operations(self):
        # Just a few for .keys()
        self.assertTrue({1:1}.keys() == {1})
        self.assertTrue({1} == {1:1}.keys())
        self.assertEqual({1:1}.keys() | {2}, {1, 2})
        self.assertEqual({2} | {1:1}.keys(), {1, 2})
        # And a few for .items()
        self.assertTrue({1:1}.items() == {(1,1)})
        self.assertTrue({(1,1)} == {1:1}.items())
        self.assertEqual({1:1}.items() | {2}, {(1,1), 2})
        self.assertEqual({2} | {1:1}.items(), {(1,1), 2})

    def test_missing(self):
        # Make sure dict doesn't have a __missing__ method
        self.assertNotHasAttr(dict, "__missing__")
        self.assertNotHasAttr({}, "__missing__")
        # Test several cases:
        # (D) subclass defines __missing__ method returning a value
        # (E) subclass defines __missing__ method raising RuntimeError
        # (F) subclass sets __missing__ instance variable (no effect)
        # (G) subclass doesn't define __missing__ at all
        class D(dict):
            def __missing__(self, key):
                return 42
        d = D({1: 2, 3: 4})
        self.assertEqual(d[1], 2)
        self.assertEqual(d[3], 4)
        self.assertNotIn(2, d)
        self.assertNotIn(2, d.keys())
        self.assertEqual(d[2], 42)

        class E(dict):
            def __missing__(self, key):
                raise RuntimeError(key)
        e = E()
        with self.assertRaises(RuntimeError) as c:
            e[42]
        self.assertEqual(c.exception.args, (42,))

        class F(dict):
            def __init__(self):
                # An instance variable __missing__ should have no effect
                self.__missing__ = lambda key: None
        f = F()
        with self.assertRaises(KeyError) as c:
            f[42]
        self.assertEqual(c.exception.args, (42,))

        class G(dict):
            pass
        g = G()
        with self.assertRaises(KeyError) as c:
            g[42]
        self.assertEqual(c.exception.args, (42,))

    def test_tuple_keyerror(self):
        # SF #1576657
        d = {}
        with self.assertRaises(KeyError) as c:
            d[(1,)]
        self.assertEqual(c.exception.args, ((1,),))

    def test_bad_key(self):
        # Dictionary lookups should fail if __eq__() raises an exception.
        class CustomException(Exception):
            pass

        class BadDictKey:
            def __hash__(self):
                return hash(self.__class__)

            def __eq__(self, other):
                if isinstance(other, self.__class__):
                    raise CustomException
                return other

        d = {}
        x1 = BadDictKey()
        x2 = BadDictKey()
        d[x1] = 1
        for stmt in ['d[x2] = 2',
                     'z = d[x2]',
                     'x2 in d',
                     'd.get(x2)',
                     'd.setdefault(x2, 42)',
                     'd.pop(x2)',
                     'd.update({x2: 2})']:
            with self.assertRaises(CustomException):
                exec(stmt, locals())

    def test_resize1(self):
        # Dict resizing bug, found by Jack Jansen in 2.2 CVS development.
        # This version got an assert failure in debug build, infinite loop in
        # release build.  Unfortunately, provoking this kind of stuff requires
        # a mix of inserts and deletes hitting exactly the right hash codes in
        # exactly the right order, and I can't think of a randomized approach
        # that would be *likely* to hit a failing case in reasonable time.

        d = {}
        for i in range(5):
            d[i] = i
        for i in range(5):
            del d[i]
        for i in range(5, 9):  # i==8 was the problem
            d[i] = i

    def test_resize2(self):
        # Another dict resizing bug (SF bug #1456209).
        # This caused Segmentation faults or Illegal instructions.

        class X(object):
            def __hash__(self):
                return 5
            def __eq__(self, other):
                if resizing:
                    d.clear()
                return False
        d = {}
        resizing = False
        d[X()] = 1
        d[X()] = 2
        d[X()] = 3
        d[X()] = 4
        d[X()] = 5
        # now trigger a resize
        resizing = True
        d[9] = 6

    def test_empty_presized_dict_in_freelist(self):
        # Bug #3537: if an empty but presized dict with a size larger
        # than 7 was in the freelist, it triggered an assertion failure
        with self.assertRaises(ZeroDivisionError):
            d = {'a': 1 // 0, 'b': None, 'c': None, 'd': None, 'e': None,
                 'f': None, 'g': None, 'h': None}
        d = {}

    def test_container_iterator(self):
        # Bug #3680: tp_traverse was not implemented for dictiter and
        # dictview objects.
        class C(object):
            pass
        views = (dict.items, dict.values, dict.keys)
        for v in views:
            obj = C()
            ref = weakref.ref(obj)
            container = {obj: 1}
            obj.v = v(container)
            obj.x = iter(obj.v)
            del obj, container
            gc.collect()
            self.assertIs(ref(), None, "Cycle was not collected")

    def make_shared_key_dict(self, n):
        class C:
            pass

        dicts = []
        for i in range(n):
            a = C()
            a.x, a.y, a.z = 1, 2, 3
            dicts.append(a.__dict__)

        return dicts

    @support.cpython_only
    def test_splittable_setdefault(self):
        """split table must keep correct insertion
        order when attributes are adding using setdefault()"""
        a, b = self.make_shared_key_dict(2)

        a['a'] = 1
        size_a = sys.getsizeof(a)
        a['b'] = 2
        b.setdefault('b', 2)
        size_b = sys.getsizeof(b)
        b['a'] = 1

        self.assertEqual(list(a), ['x', 'y', 'z', 'a', 'b'])
        self.assertEqual(list(b), ['x', 'y', 'z', 'b', 'a'])

    @support.cpython_only
    def test_splittable_del(self):
        """split table must be combined when del d[k]"""
        a, b = self.make_shared_key_dict(2)

        orig_size = sys.getsizeof(a)

        del a['y']  # split table is combined
        with self.assertRaises(KeyError):
            del a['y']

        self.assertEqual(list(a), ['x', 'z'])
        self.assertEqual(list(b), ['x', 'y', 'z'])

        # Two dicts have different insertion order.
        a['y'] = 42
        self.assertEqual(list(a), ['x', 'z', 'y'])
        self.assertEqual(list(b), ['x', 'y', 'z'])

    @support.cpython_only
    def test_splittable_pop(self):
        a, b = self.make_shared_key_dict(2)

        a.pop('y')
        with self.assertRaises(KeyError):
            a.pop('y')

        self.assertEqual(list(a), ['x', 'z'])
        self.assertEqual(list(b), ['x', 'y', 'z'])

        # Two dicts have different insertion order.
        a['y'] = 42
        self.assertEqual(list(a), ['x', 'z', 'y'])
        self.assertEqual(list(b), ['x', 'y', 'z'])

    @support.cpython_only
    def test_splittable_pop_pending(self):
        """pop a pending key in a split table should not crash"""
        a, b = self.make_shared_key_dict(2)

        a['a'] = 4
        with self.assertRaises(KeyError):
            b.pop('a')

    @support.cpython_only
    def test_splittable_popitem(self):
        """split table must be combined when d.popitem()"""
        a, b = self.make_shared_key_dict(2)

        orig_size = sys.getsizeof(a)

        item = a.popitem()  # split table is combined
        self.assertEqual(item, ('z', 3))
        with self.assertRaises(KeyError):
            del a['z']

        self.assertGreater(sys.getsizeof(a), orig_size)
        self.assertEqual(list(a), ['x', 'y'])
        self.assertEqual(list(b), ['x', 'y', 'z'])

    @support.cpython_only
    def test_splittable_update(self):
        """dict.update(other) must preserve order in other."""
        class C:
            def __init__(self, order):
                if order:
                    self.a, self.b, self.c = 1, 2, 3
                else:
                    self.c, self.b, self.a = 1, 2, 3
        o = C(True)
        o = C(False)  # o.__dict__ has reversed order.
        self.assertEqual(list(o.__dict__), ["c", "b", "a"])

        d = {}
        d.update(o.__dict__)
        self.assertEqual(list(d), ["c", "b", "a"])

    @support.cpython_only
    def test_splittable_to_generic_combinedtable(self):
        """split table must be correctly resized and converted to generic combined table"""
        class C:
            pass

        a = C()
        a.x = 1
        d = a.__dict__
        d[2] = 2 # split table is resized to a generic combined table

        self.assertEqual(list(d), ['x', 2])

    def test_iterator_pickling(self):
        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
            data = {1:"a", 2:"b", 3:"c"}
            it = iter(data)
            d = pickle.dumps(it, proto)
            it = pickle.loads(d)
            self.assertEqual(list(it), list(data))

            it = pickle.loads(d)
            try:
                drop = next(it)
            except StopIteration:
                continue
            d = pickle.dumps(it, proto)
            it = pickle.loads(d)
            del data[drop]
            self.assertEqual(list(it), list(data))

    def test_itemiterator_pickling(self):
        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
            data = {1:"a", 2:"b", 3:"c"}
            # dictviews aren't picklable, only their iterators
            itorg = iter(data.items())
            d = pickle.dumps(itorg, proto)
            it = pickle.loads(d)
            # note that the type of the unpickled iterator
            # is not necessarily the same as the original.  It is
            # merely an object supporting the iterator protocol, yielding
            # the same objects as the original one.
            # self.assertEqual(type(itorg), type(it))
            self.assertIsInstance(it, collections.abc.Iterator)
            self.assertEqual(dict(it), data)

            it = pickle.loads(d)
            drop = next(it)
            d = pickle.dumps(it, proto)
            it = pickle.loads(d)
            del data[drop[0]]
            self.assertEqual(dict(it), data)

    def test_valuesiterator_pickling(self):
        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
            data = {1:"a", 2:"b", 3:"c"}
            # data.values() isn't picklable, only its iterator
            it = iter(data.values())
            d = pickle.dumps(it, proto)
            it = pickle.loads(d)
            self.assertEqual(list(it), list(data.values()))

            it = pickle.loads(d)
            drop = next(it)
            d = pickle.dumps(it, proto)
            it = pickle.loads(d)
            values = list(it) + [drop]
            self.assertEqual(sorted(values), sorted(list(data.values())))

    def test_reverseiterator_pickling(self):
        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
            data = {1:"a", 2:"b", 3:"c"}
            it = reversed(data)
            d = pickle.dumps(it, proto)
            it = pickle.loads(d)
            self.assertEqual(list(it), list(reversed(data)))

            it = pickle.loads(d)
            try:
                drop = next(it)
            except StopIteration:
                continue
            d = pickle.dumps(it, proto)
            it = pickle.loads(d)
            del data[drop]
            self.assertEqual(list(it), list(reversed(data)))

    def test_reverseitemiterator_pickling(self):
        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
            data = {1:"a", 2:"b", 3:"c"}
            # dictviews aren't picklable, only their iterators
            itorg = reversed(data.items())
            d = pickle.dumps(itorg, proto)
            it = pickle.loads(d)
            # note that the type of the unpickled iterator
            # is not necessarily the same as the original.  It is
            # merely an object supporting the iterator protocol, yielding
            # the same objects as the original one.
            # self.assertEqual(type(itorg), type(it))
            self.assertIsInstance(it, collections.abc.Iterator)
            self.assertEqual(dict(it), data)

            it = pickle.loads(d)
            drop = next(it)
            d = pickle.dumps(it, proto)
            it = pickle.loads(d)
            del data[drop[0]]
            self.assertEqual(dict(it), data)

    def test_reversevaluesiterator_pickling(self):
        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
            data = {1:"a", 2:"b", 3:"c"}
            # data.values() isn't picklable, only its iterator
            it = reversed(data.values())
            d = pickle.dumps(it, proto)
            it = pickle.loads(d)
            self.assertEqual(list(it), list(reversed(data.values())))

            it = pickle.loads(d)
            drop = next(it)
            d = pickle.dumps(it, proto)
            it = pickle.loads(d)
            values = list(it) + [drop]
            self.assertEqual(sorted(values), sorted(data.values()))

    def test_instance_dict_getattr_str_subclass(self):
        class Foo:
            def __init__(self, msg):
                self.msg = msg
        f = Foo('123')
        class _str(str):
            pass
        self.assertEqual(f.msg, getattr(f, _str('msg')))
        self.assertEqual(f.msg, f.__dict__[_str('msg')])

    def test_object_set_item_single_instance_non_str_key(self):
        class Foo: pass
        f = Foo()
        f.__dict__[1] = 1
        f.a = 'a'
        self.assertEqual(f.__dict__, {1:1, 'a':'a'})

    def check_reentrant_insertion(self, mutate):
        # This object will trigger mutation of the dict when replaced
        # by another value.  Note this relies on refcounting: the test
        # won't achieve its purpose on fully-GCed Python implementations.
        class Mutating:
            def __del__(self):
                mutate(d)

        d = {k: Mutating() for k in 'abcdefghijklmnopqr'}
        for k in list(d):
            d[k] = k

    def test_reentrant_insertion(self):
        # Reentrant insertion shouldn't crash (see issue #22653)
        def mutate(d):
            d['b'] = 5
        self.check_reentrant_insertion(mutate)

        def mutate(d):
            d.update(self.__dict__)
            d.clear()
        self.check_reentrant_insertion(mutate)

        def mutate(d):
            while d:
                d.popitem()
        self.check_reentrant_insertion(mutate)

    def test_merge_and_mutate(self):
        class X:
            def __hash__(self):
                return 0

            def __eq__(self, o):
                other.clear()
                return False

        l = [(i,0) for i in range(1, 1337)]
        other = dict(l)
        other[X()] = 0
        d = {X(): 0, 1: 1}
        self.assertRaises(RuntimeError, d.update, other)

    def test_free_after_iterating(self):
        support.check_free_after_iterating(self, iter, dict)
        support.check_free_after_iterating(self, lambda d: iter(d.keys()), dict)
        support.check_free_after_iterating(self, lambda d: iter(d.values()), dict)
        support.check_free_after_iterating(self, lambda d: iter(d.items()), dict)

    def test_equal_operator_modifying_operand(self):
        # test fix for seg fault reported in bpo-27945 part 3.
        class X():
            def __del__(self):
                dict_b.clear()

            def __eq__(self, other):
                dict_a.clear()
                return True

            def __hash__(self):
                return 13

        dict_a = {X(): 0}
        dict_b = {X(): X()}
        self.assertTrue(dict_a == dict_b)

        # test fix for seg fault reported in bpo-38588 part 1.
        class Y:
            def __eq__(self, other):
                dict_d.clear()
                return True

        dict_c = {0: Y()}
        dict_d = {0: set()}
        self.assertTrue(dict_c == dict_d)

    def test_fromkeys_operator_modifying_dict_operand(self):
        # test fix for seg fault reported in issue 27945 part 4a.
        class X(int):
            def __hash__(self):
                return 13

            def __eq__(self, other):
                if len(d) > 1:
                    d.clear()
                return False

        d = {}  # this is required to exist so that d can be constructed!
        d = {X(1): 1, X(2): 2}
        try:
            dict.fromkeys(d)  # shouldn't crash
        except RuntimeError:  # implementation defined
            pass

    def test_fromkeys_operator_modifying_set_operand(self):
        # test fix for seg fault reported in issue 27945 part 4b.
        class X(int):
            def __hash__(self):
                return 13

            def __eq__(self, other):
                if len(d) > 1:
                    d.clear()
                return False

        d = {}  # this is required to exist so that d can be constructed!
        d = {X(1), X(2)}
        try:
            dict.fromkeys(d)  # shouldn't crash
        except RuntimeError:  # implementation defined
            pass

    def test_dictitems_contains_use_after_free(self):
        class X:
            def __eq__(self, other):
                d.clear()
                return NotImplemented

        d = {0: set()}
        (0, X()) in d.items()

    def test_dict_contain_use_after_free(self):
        # bpo-40489
        class S(str):
            def __eq__(self, other):
                d.clear()
                return NotImplemented

            def __hash__(self):
                return hash('test')

        d = {S(): 'value'}
        self.assertFalse('test' in d)

    def test_init_use_after_free(self):
        class X:
            def __hash__(self):
                pair[:] = []
                return 13

        pair = [X(), 123]
        dict([pair])

    def test_oob_indexing_dictiter_iternextitem(self):
        class X(int):
            def __del__(self):
                d.clear()

        d = {i: X(i) for i in range(8)}

        def iter_and_mutate():
            for result in d.items():
                if result[0] == 2:
                    d[2] = None # free d[2] --> X(2).__del__ was called

        self.assertRaises(RuntimeError, iter_and_mutate)

    def test_reversed(self):
        d = {"a": 1, "b": 2, "foo": 0, "c": 3, "d": 4}
        del d["foo"]
        r = reversed(d)
        self.assertEqual(list(r), list('dcba'))
        self.assertRaises(StopIteration, next, r)

    def test_reverse_iterator_for_empty_dict(self):
        # bpo-38525: reversed iterator should work properly

        # empty dict is directly used for reference count test
        self.assertEqual(list(reversed({})), [])
        self.assertEqual(list(reversed({}.items())), [])
        self.assertEqual(list(reversed({}.values())), [])
        self.assertEqual(list(reversed({}.keys())), [])

        # dict() and {} don't trigger the same code path
        self.assertEqual(list(reversed(dict())), [])
        self.assertEqual(list(reversed(dict().items())), [])
        self.assertEqual(list(reversed(dict().values())), [])
        self.assertEqual(list(reversed(dict().keys())), [])

    def test_reverse_iterator_for_shared_shared_dicts(self):
        class A:
            def __init__(self, x, y):
                if x: self.x = x
                if y: self.y = y

        self.assertEqual(list(reversed(A(1, 2).__dict__)), ['y', 'x'])
        self.assertEqual(list(reversed(A(1, 0).__dict__)), ['x'])
        self.assertEqual(list(reversed(A(0, 1).__dict__)), ['y'])

    def test_dict_copy_order(self):
        # bpo-34320
        od = collections.OrderedDict([('a', 1), ('b', 2)])
        od.move_to_end('a')
        expected = list(od.items())

        copy = dict(od)
        self.assertEqual(list(copy.items()), expected)

        # dict subclass doesn't override __iter__
        class CustomDict(dict):
            pass

        pairs = [('a', 1), ('b', 2), ('c', 3)]

        d = CustomDict(pairs)
        self.assertEqual(pairs, list(dict(d).items()))

        class CustomReversedDict(dict):
            def keys(self):
                return reversed(list(dict.keys(self)))

            __iter__ = keys

            def items(self):
                return reversed(dict.items(self))

        d = CustomReversedDict(pairs)
        self.assertEqual(pairs[::-1], list(dict(d).items()))

    @support.cpython_only
    def test_dict_items_result_gc(self):
        # bpo-42536: dict.items's tuple-reuse speed trick breaks the GC's
        # assumptions about what can be untracked. Make sure we re-track result
        # tuples whenever we reuse them.
        it = iter({None: []}.items())
        gc.collect()
        # That GC collection probably untracked the recycled internal result
        # tuple, which is initialized to (None, None). Make sure it's re-tracked
        # when it's mutated and returned from __next__:
        self.assertTrue(gc.is_tracked(next(it)))

    @support.cpython_only
    def test_dict_items_result_gc_reversed(self):
        # Same as test_dict_items_result_gc above, but reversed.
        it = reversed({None: []}.items())
        gc.collect()
        self.assertTrue(gc.is_tracked(next(it)))

    def test_store_evilattr(self):
        class EvilAttr:
            def __init__(self, d):
                self.d = d

            def __del__(self):
                if 'attr' in self.d:
                    del self.d['attr']
                gc.collect()

        class Obj:
            pass

        obj = Obj()
        obj.__dict__ = {}
        for _ in range(10):
            obj.attr = EvilAttr(obj.__dict__)

    def test_str_nonstr(self):
        # cpython uses a different lookup function if the dict only contains
        # `str` keys. Make sure the unoptimized path is used when a non-`str`
        # key appears.

        class StrSub(str):
            pass

        eq_count = 0
        # This class compares equal to the string 'key3'
        class Key3:
            def __hash__(self):
                return hash('key3')

            def __eq__(self, other):
                nonlocal eq_count
                if isinstance(other, Key3) or isinstance(other, str) and other == 'key3':
                    eq_count += 1
                    return True
                return False

        key3_1 = StrSub('key3')
        key3_2 = Key3()
        key3_3 = Key3()

        dicts = []

        # Create dicts of the form `{'key1': 42, 'key2': 43, key3: 44}` in a
        # bunch of different ways. In all cases, `key3` is not of type `str`.
        # `key3_1` is a `str` subclass and `key3_2` is a completely unrelated
        # type.
        for key3 in (key3_1, key3_2):
            # A literal
            dicts.append({'key1': 42, 'key2': 43, key3: 44})

            # key3 inserted via `dict.__setitem__`
            d = {'key1': 42, 'key2': 43}
            d[key3] = 44
            dicts.append(d)

            # key3 inserted via `dict.setdefault`
            d = {'key1': 42, 'key2': 43}
            self.assertEqual(d.setdefault(key3, 44), 44)
            dicts.append(d)

            # key3 inserted via `dict.update`
            d = {'key1': 42, 'key2': 43}
            d.update({key3: 44})
            dicts.append(d)

            # key3 inserted via `dict.__ior__`
            d = {'key1': 42, 'key2': 43}
            d |= {key3: 44}
            dicts.append(d)

            # `dict(iterable)`
            def make_pairs():
                yield ('key1', 42)
                yield ('key2', 43)
                yield (key3, 44)
            d = dict(make_pairs())
            dicts.append(d)

            # `dict.copy`
            d = d.copy()
            dicts.append(d)

            # dict comprehension
            d = {key: 42 + i for i,key in enumerate(['key1', 'key2', key3])}
            dicts.append(d)

        for d in dicts:
            with self.subTest(d=d):
                self.assertEqual(d.get('key1'), 42)

                # Try to make an object that is of type `str` and is equal to
                # `'key1'`, but (at least on cpython) is a different object.
                noninterned_key1 = 'ke'
                noninterned_key1 += 'y1'
                if support.check_impl_detail(cpython=True):
                    # suppress a SyntaxWarning
                    interned_key1 = 'key1'
                    self.assertFalse(noninterned_key1 is interned_key1)
                self.assertEqual(d.get(noninterned_key1), 42)

                self.assertEqual(d.get('key3'), 44)
                self.assertEqual(d.get(key3_1), 44)
                self.assertEqual(d.get(key3_2), 44)

                # `key3_3` itself is definitely not a dict key, so make sure
                # that `__eq__` gets called.
                #
                # Note that this might not hold for `key3_1` and `key3_2`
                # because they might be the same object as one of the dict keys,
                # in which case implementations are allowed to skip the call to
                # `__eq__`.
                eq_count = 0
                self.assertEqual(d.get(key3_3), 44)
                self.assertGreaterEqual(eq_count, 1)

    def test_overwrite_managed_dict(self):
        # GH-130327: Overwriting an object's managed dictionary with another object's
        # skipped traversal in favor of inline values, causing the GC to believe that
        # the __dict__ wasn't reachable.
        import gc

        class Shenanigans:
            pass

        to_be_deleted = Shenanigans()
        to_be_deleted.attr = "whatever"
        holds_reference = Shenanigans()
        holds_reference.__dict__ = to_be_deleted.__dict__
        holds_reference.ref = {"circular": to_be_deleted, "data": 42}

        del to_be_deleted
        gc.collect()
        self.assertEqual(holds_reference.ref['data'], 42)
        self.assertEqual(holds_reference.attr, "whatever")

    def test_unhashable_key(self):
        d = {'a': 1}
        key = [1, 2, 3]

        def check_unhashable_key():
            msg = "cannot use 'list' as a dict key (unhashable type: 'list')"
            return self.assertRaisesRegex(TypeError, re.escape(msg))

        with check_unhashable_key():
            key in d
        with check_unhashable_key():
            d[key]
        with check_unhashable_key():
            d[key] = 2
        with check_unhashable_key():
            d.setdefault(key, 2)
        with check_unhashable_key():
            d.pop(key)
        with check_unhashable_key():
            d.get(key)

        # Only TypeError exception is overridden,
        # other exceptions are left unchanged.
        class HashError:
            def __hash__(self):
                raise KeyError('error')

        key2 = HashError()
        with self.assertRaises(KeyError):
            key2 in d
        with self.assertRaises(KeyError):
            d[key2]
        with self.assertRaises(KeyError):
            d[key2] = 2
        with self.assertRaises(KeyError):
            d.setdefault(key2, 2)
        with self.assertRaises(KeyError):
            d.pop(key2)
        with self.assertRaises(KeyError):
            d.get(key2)

    def test_clear_at_lookup(self):
        # gh-140551 dict crash if clear is called at lookup stage
        class X:
            def __hash__(self):
                return 1
            def __eq__(self, other):
                nonlocal d
                d.clear()

        d = {}
        for _ in range(10):
            d[X()] = None

        self.assertEqual(len(d), 1)

        d = {}
        for _ in range(10):
            d.setdefault(X(), None)

        self.assertEqual(len(d), 1)

    def test_split_table_update_with_str_subclass(self):
        # gh-142218: inserting into a split table dictionary with a non str
        # key that matches an existing key.
        class MyStr(str): pass
        class MyClass: pass
        obj = MyClass()
        obj.attr = 1
        obj.__dict__[MyStr('attr')] = 2
        self.assertEqual(obj.attr, 2)

    def test_split_table_insert_with_str_subclass(self):
        # gh-143189: inserting into split table dictionary with a non str
        # key that matches an existing key in the shared table but not in
        # the dict yet.

        class MyStr(str): pass
        class MyClass: pass

        obj = MyClass()
        obj.attr1 = 1

        obj2 = MyClass()
        d = obj2.__dict__
        d[MyStr("attr1")] = 2
        self.assertIsInstance(list(d)[0], MyStr)

    def test_hash_collision_remove_add(self):
        self.maxDiff = None
        # There should be enough space, so all elements with unique hash
        # will be placed in corresponding cells without collision.
        n = 64
        items = [(CustomHash(h), h) for h in range(n)]
        # Keys with hash collision.
        a = CustomHash(n)
        b = CustomHash(n)
        items += [(a, 'a'), (b, 'b')]
        d = dict(items)
        self.assertEqual(len(d), len(items), d)
        del d[a]
        # "a" has been replaced with a dummy.
        del items[n]
        self.assertEqual(len(d), len(items), d)
        self.assertEqual(d, dict(items))
        d[b] = 'c'
        # "b" should not replace the dummy.
        items[n] = (b, 'c')
        self.assertEqual(len(d), len(items), d)
        self.assertEqual(d, dict(items))

    def test_clear_reentrant_embedded(self):
        # gh-130555: dict.clear() must be safe when values are embedded
        # in an object and a destructor mutates the dict.
        class MyObj: pass
        class ClearOnDelete:
            def __del__(self):
                nonlocal x
                del x

        x = MyObj()
        x.a = ClearOnDelete()

        d = x.__dict__
        d.clear()

    def test_clear_reentrant_cycle(self):
        # gh-130555: dict.clear() must be safe for embedded dicts when the
        # object is part of a reference cycle and the last reference to the
        # dict is via the cycle.
        class MyObj: pass
        obj = MyObj()
        obj.f = obj
        obj.attr = "attr"

        d = obj.__dict__
        del obj

        d.clear()

    def test_clear_reentrant_force_combined(self):
        # gh-130555: dict.clear() must be safe when a destructor forces the
        # dict from embedded/split to combined (setting ma_values to NULL).
        class MyObj: pass
        class ForceConvert:
            def __del__(self):
                d[1] = "trigger"

        x = MyObj()
        x.a = ForceConvert()
        x.b = "other"

        d = x.__dict__
        d.clear()

    def test_clear_reentrant_delete(self):
        # gh-130555: dict.clear() must be safe when a destructor deletes
        # a key from the same embedded dict.
        class MyObj: pass
        class DelKey:
            def __del__(self):
                try:
                    del d['b']
                except KeyError:
                    pass

        x = MyObj()
        x.a = DelKey()
        x.b = "value_b"
        x.c = "value_c"

        d = x.__dict__
        d.clear()


class CAPITest(unittest.TestCase):

    # Test _PyDict_GetItem_KnownHash()
    @support.cpython_only
    def test_getitem_knownhash(self):
        _testinternalcapi = import_helper.import_module('_testinternalcapi')
        dict_getitem_knownhash = _testinternalcapi.dict_getitem_knownhash

        d = {'x': 1, 'y': 2, 'z': 3}
        self.assertEqual(dict_getitem_knownhash(d, 'x', hash('x')), 1)
        self.assertEqual(dict_getitem_knownhash(d, 'y', hash('y')), 2)
        self.assertEqual(dict_getitem_knownhash(d, 'z', hash('z')), 3)

        # not a dict
        self.assertRaises(SystemError, dict_getitem_knownhash, [], 1, hash(1))
        # key does not exist
        self.assertRaises(KeyError, dict_getitem_knownhash, {}, 1, hash(1))

        class Exc(Exception): pass
        class BadEq:
            def __eq__(self, other):
                raise Exc
            def __hash__(self):
                return 7

        k1, k2 = BadEq(), BadEq()
        d = {k1: 1}
        self.assertEqual(dict_getitem_knownhash(d, k1, hash(k1)), 1)
        self.assertRaises(Exc, dict_getitem_knownhash, d, k2, hash(k2))


from test import mapping_tests

class GeneralMappingTests(mapping_tests.BasicTestMappingProtocol):
    type2test = dict

class Dict(dict):
    pass

class SubclassMappingTests(mapping_tests.BasicTestMappingProtocol):
    type2test = Dict

class FrozenDictMappingTests(mapping_tests.BasicTestImmutableMappingProtocol):
    type2test = frozendict


class FrozenDict(frozendict):
    pass


class FrozenDictSlots(frozendict):
    __slots__ = ('slot_attr',)


class FrozenDictTests(unittest.TestCase):
    def test_constructor(self):
        # frozendict.__init__() has no effect
        d = frozendict(a=1, b=2, c=3)
        d.__init__(x=1)
        self.assertEqual(d, frozendict(a=1, b=2, c=3))

        # dict constructor cannot be used on frozendict
        with self.assertRaises(TypeError):
            dict.__init__(d, x=1)

        # Avoid copy if it's frozendict type
        d2 = frozendict(d)
        self.assertIs(d2, d)
        d2 = FrozenDict(d)
        self.assertIsNot(d2, d)
        self.assertEqual(d2, d)

    def test_copy(self):
        d = frozendict(x=1, y=2)
        d2 = d.copy()
        self.assertIs(d2, d)

        d = FrozenDict(x=1, y=2)
        d2 = d.copy()
        self.assertIsNot(d2, d)
        self.assertEqual(d2, frozendict(x=1, y=2))
        self.assertEqual(type(d2), frozendict)

    def test_merge(self):
        # test "a | b" operator
        self.assertEqual(frozendict(x=1) | frozendict(y=2),
                         frozendict({'x': 1, 'y': 2}))
        self.assertEqual(frozendict(x=1) | dict(y=2),
                         frozendict({'x': 1, 'y': 2}))
        self.assertEqual(frozendict(x=1, y=2) | frozendict(y=5),
                         frozendict({'x': 1, 'y': 5}))
        self.assertEqual(FrozenDict(x=1, y=2) | FrozenDict(y=5),
                         frozendict({'x': 1, 'y': 5}))

        fd = frozendict(x=1, y=2)
        self.assertIs(fd | frozendict(), fd)
        self.assertIs(fd | {}, fd)
        self.assertIs(frozendict() | fd, fd)

        fd = FrozenDict(x=1, y=2)
        self.assertEqual(fd | frozendict(), fd)
        self.assertEqual(fd | {}, fd)
        self.assertEqual(frozendict() | fd, fd)

    def test_update(self):
        # test "a |= b" operator
        d = frozendict(x=1)
        copy = d
        self.assertIs(copy, d)
        d |= frozendict(y=2)
        self.assertIsNot(copy, d)
        self.assertEqual(d, frozendict({'x': 1, 'y': 2}))
        self.assertEqual(copy, frozendict({'x': 1}))

    def test_items_xor(self):
        # test "a ^ b" operator on items views
        res = frozendict(a=1, b=2).items() ^ frozendict(b=2, c=3).items()
        self.assertEqual(res, {('a', 1), ('c', 3)})

    def test_repr(self):
        d = frozendict()
        self.assertEqual(repr(d), "frozendict()")

        d = frozendict(x=1, y=2)
        self.assertEqual(repr(d), "frozendict({'x': 1, 'y': 2})")

        d = FrozenDict(x=1, y=2)
        self.assertEqual(repr(d), "FrozenDict({'x': 1, 'y': 2})")

    def test_hash(self):
        # hash() doesn't rely on the items order
        self.assertEqual(hash(frozendict(x=1, y=2)),
                         hash(frozendict(y=2, x=1)))

        fd = frozendict(x=[1], y=[2])
        with self.assertRaisesRegex(TypeError, "unhashable type: 'list'"):
            hash(fd)

    def test_fromkeys(self):
        self.assertEqual(frozendict.fromkeys('abc'),
                         frozendict(a=None, b=None, c=None))

        # Subclass which overrides the constructor
        created = frozendict(x=1)
        class FrozenDictSubclass(frozendict):
            def __new__(self):
                return created

        fd = FrozenDictSubclass.fromkeys("abc")
        self.assertEqual(fd, frozendict(x=1, a=None, b=None, c=None))
        self.assertEqual(type(fd), FrozenDictSubclass)
        self.assertEqual(created, frozendict(x=1))

        fd = FrozenDictSubclass.fromkeys(frozendict(y=2))
        self.assertEqual(fd, frozendict(x=1, y=None))
        self.assertEqual(type(fd), FrozenDictSubclass)
        self.assertEqual(created, frozendict(x=1))

        # Subclass which doesn't override the constructor
        class FrozenDictSubclass2(frozendict):
            pass

        fd = FrozenDictSubclass2.fromkeys("abc")
        self.assertEqual(fd, frozendict(a=None, b=None, c=None))
        self.assertEqual(type(fd), FrozenDictSubclass2)

        # Dict subclass which overrides the constructor
        class DictSubclass(dict):
            def __new__(self):
                return created

        fd = DictSubclass.fromkeys("abc")
        self.assertEqual(fd, frozendict(x=1, a=None, b=None, c=None))
        self.assertEqual(type(fd), DictSubclass)
        self.assertEqual(created, frozendict(x=1))

    def test_pickle(self):
        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
            for fd in (
                frozendict(),
                frozendict(x=1, y=2),
                FrozenDict(x=1, y=2),
                FrozenDictSlots(x=1, y=2),
            ):
                if type(fd) == FrozenDict:
                    fd.attr = 123
                if type(fd) == FrozenDictSlots:
                    fd.slot_attr = 456
                with self.subTest(fd=fd, proto=proto):
                    if proto >= 2:
                        p = pickle.dumps(fd, proto)
                        fd2 = pickle.loads(p)
                        self.assertEqual(fd2, fd)
                        self.assertEqual(type(fd2), type(fd))
                        if type(fd) == FrozenDict:
                            self.assertEqual(fd2.attr, 123)
                        if type(fd) == FrozenDictSlots:
                            self.assertEqual(fd2.slot_attr, 456)
                    else:
                        # protocol 0 and 1 don't support frozendict
                        with self.assertRaises(TypeError):
                            pickle.dumps(fd, proto)

    def test_pickle_iter(self):
        fd = frozendict(c=1, b=2, a=3, d=4, e=5, f=6)
        for method_name in (None, 'keys', 'values', 'items'):
            if method_name is not None:
                meth = getattr(fd, method_name)
            else:
                meth = lambda: fd
            expected = list(meth())[1:]
            for proto in range(pickle.HIGHEST_PROTOCOL + 1):
                with self.subTest(method_name=method_name, protocol=proto):
                    it = iter(meth())
                    next(it)
                    p = pickle.dumps(it, proto)
                    unpickled = pickle.loads(p)
                    self.assertEqual(list(unpickled), expected)
                    self.assertEqual(list(it), expected)

    def test_unhashable_key(self):
        d = frozendict(a=1)
        key = [1, 2, 3]

        def check_unhashable_key():
            msg = "cannot use 'list' as a frozendict key (unhashable type: 'list')"
            return self.assertRaisesRegex(TypeError, re.escape(msg))

        with check_unhashable_key():
            key in d
        with check_unhashable_key():
            d[key]
        with check_unhashable_key():
            d.get(key)

        # Only TypeError exception is overridden,
        # other exceptions are left unchanged.
        class HashError:
            def __hash__(self):
                raise KeyError('error')

        key2 = HashError()
        with self.assertRaises(KeyError):
            key2 in d
        with self.assertRaises(KeyError):
            d[key2]
        with self.assertRaises(KeyError):
            d.get(key2)


if __name__ == "__main__":
    unittest.main()