cpython/Lib/test/mapping_tests.py

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# tests common to dict and UserDict
import unittest
import UserDict
class BasicTestMappingProtocol(unittest.TestCase):
# This base class can be used to check that an object conforms to the
# mapping protocol
# Functions that can be useful to override to adapt to dictionary
# semantics
type2test = None # which class is being tested (overwrite in subclasses)
def _reference(self):
"""Return a dictionary of values which are invariant by storage
in the object under test."""
return {1:2, "key1":"value1", "key2":(1,2,3)}
def _empty_mapping(self):
"""Return an empty mapping object"""
return self.type2test()
def _full_mapping(self, data):
"""Return a mapping object with the value contained in data
dictionary"""
x = self._empty_mapping()
for key, value in data.items():
x[key] = value
return x
def __init__(self, *args, **kw):
unittest.TestCase.__init__(self, *args, **kw)
self.reference = self._reference().copy()
# A (key, value) pair not in the mapping
key, value = self.reference.popitem()
self.other = {key:value}
# A (key, value) pair in the mapping
key, value = self.reference.popitem()
self.inmapping = {key:value}
self.reference[key] = value
def test_read(self):
# Test for read only operations on mapping
p = self._empty_mapping()
p1 = dict(p) #workaround for singleton objects
d = self._full_mapping(self.reference)
if d is p:
p = p1
#Indexing
for key, value in self.reference.items():
self.assertEqual(d[key], value)
knownkey = self.other.keys()[0]
self.failUnlessRaises(KeyError, lambda:d[knownkey])
#len
self.assertEqual(len(p), 0)
self.assertEqual(len(d), len(self.reference))
#__contains__
for k in self.reference:
self.assert_(k in d)
for k in self.other:
self.failIf(k in d)
#cmp
Restructure comparison dramatically. There is no longer a default *ordering* between objects; there is only a default equality test (defined by an object being equal to itself only). Read the comment in object.c. The current implementation never uses a three-way comparison to compute a rich comparison, but it does use a rich comparison to compute a three-way comparison. I'm not quite done ripping out all the calls to PyObject_Compare/Cmp, or replacing tp_compare implementations with tp_richcompare implementations; but much of that has happened (to make most unit tests pass). The following tests still fail, because I need help deciding or understanding: test_codeop -- depends on comparing code objects test_datetime -- need Tim Peters' opinion test_marshal -- depends on comparing code objects test_mutants -- need help understanding it The problem with test_codeop and test_marshal is this: these tests compare two different code objects and expect them to be equal. Is that still a feature we'd like to support? I've temporarily removed the comparison and hash code from code objects, so they use the default (equality by pointer only) comparison. For the other two tests, run them to see for yourself. (There may be more failing test with "-u all".) A general problem with getting lots of these tests to pass is the reality that for object types that have a natural total ordering, implementing __cmp__ is much more convenient than implementing __eq__, __ne__, __lt__, and so on. Should we go back to allowing __cmp__ to provide a total ordering? Should we provide some other way to implement rich comparison with a single method override? Alex proposed a __key__() method; I've considered a __richcmp__() method. Or perhaps __cmp__() just shouldn't be killed off...
2006-08-23 21:41:19 -03:00
self.assertEqual(p, p)
self.assertEqual(d, d)
self.assertNotEqual(p, d)
self.assertNotEqual(d, p)
#__non__zero__
if p: self.fail("Empty mapping must compare to False")
if not d: self.fail("Full mapping must compare to True")
# keys(), items(), iterkeys() ...
def check_iterandlist(iter, lst, ref):
self.assert_(hasattr(iter, 'next'))
self.assert_(hasattr(iter, '__iter__'))
x = list(iter)
self.assert_(set(x)==set(lst)==set(ref))
check_iterandlist(d.iterkeys(), d.keys(), self.reference.keys())
check_iterandlist(iter(d), d.keys(), self.reference.keys())
check_iterandlist(d.itervalues(), d.values(), self.reference.values())
check_iterandlist(d.iteritems(), d.items(), self.reference.items())
#get
key, value = d.iteritems().next()
knownkey, knownvalue = self.other.iteritems().next()
self.assertEqual(d.get(key, knownvalue), value)
self.assertEqual(d.get(knownkey, knownvalue), knownvalue)
self.failIf(knownkey in d)
def test_write(self):
# Test for write operations on mapping
p = self._empty_mapping()
#Indexing
for key, value in self.reference.items():
p[key] = value
self.assertEqual(p[key], value)
for key in self.reference.keys():
del p[key]
self.failUnlessRaises(KeyError, lambda:p[key])
p = self._empty_mapping()
#update
p.update(self.reference)
self.assertEqual(dict(p), self.reference)
items = p.items()
p = self._empty_mapping()
p.update(items)
self.assertEqual(dict(p), self.reference)
d = self._full_mapping(self.reference)
#setdefault
key, value = d.iteritems().next()
knownkey, knownvalue = self.other.iteritems().next()
self.assertEqual(d.setdefault(key, knownvalue), value)
self.assertEqual(d[key], value)
self.assertEqual(d.setdefault(knownkey, knownvalue), knownvalue)
self.assertEqual(d[knownkey], knownvalue)
#pop
self.assertEqual(d.pop(knownkey), knownvalue)
self.failIf(knownkey in d)
self.assertRaises(KeyError, d.pop, knownkey)
default = 909
d[knownkey] = knownvalue
self.assertEqual(d.pop(knownkey, default), knownvalue)
self.failIf(knownkey in d)
self.assertEqual(d.pop(knownkey, default), default)
#popitem
key, value = d.popitem()
self.failIf(key in d)
self.assertEqual(value, self.reference[key])
p=self._empty_mapping()
self.assertRaises(KeyError, p.popitem)
def test_constructor(self):
self.assertEqual(self._empty_mapping(), self._empty_mapping())
def test_bool(self):
self.assert_(not self._empty_mapping())
self.assert_(self.reference)
self.assert_(bool(self._empty_mapping()) is False)
self.assert_(bool(self.reference) is True)
def test_keys(self):
d = self._empty_mapping()
self.assertEqual(d.keys(), [])
d = self.reference
self.assert_(self.inmapping.keys()[0] in d.keys())
self.assert_(self.other.keys()[0] not in d.keys())
self.assertRaises(TypeError, d.keys, None)
def test_values(self):
d = self._empty_mapping()
self.assertEqual(d.values(), [])
self.assertRaises(TypeError, d.values, None)
def test_items(self):
d = self._empty_mapping()
self.assertEqual(d.items(), [])
self.assertRaises(TypeError, d.items, None)
def test_len(self):
d = self._empty_mapping()
self.assertEqual(len(d), 0)
def test_getitem(self):
d = self.reference
self.assertEqual(d[self.inmapping.keys()[0]], self.inmapping.values()[0])
self.assertRaises(TypeError, d.__getitem__)
def test_update(self):
# mapping argument
d = self._empty_mapping()
d.update(self.other)
self.assertEqual(d.items(), self.other.items())
# No argument
d = self._empty_mapping()
d.update()
self.assertEqual(d, self._empty_mapping())
# item sequence
d = self._empty_mapping()
d.update(self.other.items())
self.assertEqual(d.items(), self.other.items())
# Iterator
d = self._empty_mapping()
d.update(self.other.iteritems())
self.assertEqual(d.items(), self.other.items())
# FIXME: Doesn't work with UserDict
# self.assertRaises((TypeError, AttributeError), d.update, None)
self.assertRaises((TypeError, AttributeError), d.update, 42)
outerself = self
class SimpleUserDict:
def __init__(self):
self.d = outerself.reference
def keys(self):
return self.d.keys()
def __getitem__(self, i):
return self.d[i]
d.clear()
d.update(SimpleUserDict())
i1 = d.items()
i2 = self.reference.items()
i1.sort()
i2.sort()
self.assertEqual(i1, i2)
class Exc(Exception): pass
d = self._empty_mapping()
class FailingUserDict:
def keys(self):
raise Exc
self.assertRaises(Exc, d.update, FailingUserDict())
d.clear()
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())
d = self._empty_mapping()
class badseq(object):
def __iter__(self):
return self
def next(self):
raise Exc()
self.assertRaises(Exc, d.update, badseq())
self.assertRaises(ValueError, d.update, [(1, 2, 3)])
# no test_fromkeys or test_copy as both os.environ and selves don't support it
def test_get(self):
d = self._empty_mapping()
self.assert_(d.get(self.other.keys()[0]) is None)
self.assertEqual(d.get(self.other.keys()[0], 3), 3)
d = self.reference
self.assert_(d.get(self.other.keys()[0]) is None)
self.assertEqual(d.get(self.other.keys()[0], 3), 3)
self.assertEqual(d.get(self.inmapping.keys()[0]), self.inmapping.values()[0])
self.assertEqual(d.get(self.inmapping.keys()[0], 3), self.inmapping.values()[0])
self.assertRaises(TypeError, d.get)
self.assertRaises(TypeError, d.get, None, None, None)
def test_setdefault(self):
d = self._empty_mapping()
self.assertRaises(TypeError, d.setdefault)
def test_popitem(self):
d = self._empty_mapping()
self.assertRaises(KeyError, d.popitem)
self.assertRaises(TypeError, d.popitem, 42)
def test_pop(self):
d = self._empty_mapping()
k, v = self.inmapping.items()[0]
d[k] = v
self.assertRaises(KeyError, d.pop, self.other.keys()[0])
self.assertEqual(d.pop(k), v)
self.assertEqual(len(d), 0)
self.assertRaises(KeyError, d.pop, k)
class TestMappingProtocol(BasicTestMappingProtocol):
def test_constructor(self):
BasicTestMappingProtocol.test_constructor(self)
self.assert_(self._empty_mapping() is not self._empty_mapping())
self.assertEqual(self.type2test(x=1, y=2), {"x": 1, "y": 2})
def test_bool(self):
BasicTestMappingProtocol.test_bool(self)
self.assert_(not self._empty_mapping())
self.assert_(self._full_mapping({"x": "y"}))
self.assert_(bool(self._empty_mapping()) is False)
self.assert_(bool(self._full_mapping({"x": "y"})) is True)
def test_keys(self):
BasicTestMappingProtocol.test_keys(self)
d = self._empty_mapping()
self.assertEqual(d.keys(), [])
d = self._full_mapping({'a': 1, 'b': 2})
k = d.keys()
self.assert_('a' in k)
self.assert_('b' in k)
self.assert_('c' not in k)
def test_values(self):
BasicTestMappingProtocol.test_values(self)
d = self._full_mapping({1:2})
self.assertEqual(d.values(), [2])
def test_items(self):
BasicTestMappingProtocol.test_items(self)
d = self._full_mapping({1:2})
self.assertEqual(d.items(), [(1, 2)])
def test_contains(self):
d = self._empty_mapping()
self.assert_(not ('a' in d))
self.assert_('a' not in d)
d = self._full_mapping({'a': 1, 'b': 2})
self.assert_('a' in d)
self.assert_('b' in d)
self.assert_('c' not in d)
self.assertRaises(TypeError, d.__contains__)
def test_len(self):
BasicTestMappingProtocol.test_len(self)
d = self._full_mapping({'a': 1, 'b': 2})
self.assertEqual(len(d), 2)
def test_getitem(self):
BasicTestMappingProtocol.test_getitem(self)
d = self._full_mapping({'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__)
def test_clear(self):
d = self._full_mapping({1:1, 2:2, 3:3})
d.clear()
self.assertEqual(d, {})
self.assertRaises(TypeError, d.clear, None)
def test_update(self):
BasicTestMappingProtocol.test_update(self)
# mapping argument
d = self._empty_mapping()
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})
# no argument
d.update()
self.assertEqual(d, {1:1, 2:2, 3:3})
# keyword arguments
d = self._empty_mapping()
d.update(x=100)
d.update(y=20)
d.update(x=1, y=2, z=3)
self.assertEqual(d, {"x":1, "y":2, "z":3})
# item sequence
d = self._empty_mapping()
d.update([("x", 100), ("y", 20)])
self.assertEqual(d, {"x":100, "y":20})
# Both item sequence and keyword arguments
d = self._empty_mapping()
d.update([("x", 100), ("y", 20)], x=1, y=2)
self.assertEqual(d, {"x":1, "y":2})
# iterator
d = self._full_mapping({1:3, 2:4})
d.update(self._full_mapping({1:2, 3:4, 5:6}).iteritems())
self.assertEqual(d, {1:2, 2:4, 3:4, 5:6})
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})
def test_fromkeys(self):
self.assertEqual(self.type2test.fromkeys('abc'), {'a':None, 'b':None, 'c':None})
d = self._empty_mapping()
self.assert_(not(d.fromkeys('abc') is 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(self.type2test): pass
self.assertEqual(dictlike.fromkeys('a'), {'a':None})
self.assertEqual(dictlike().fromkeys('a'), {'a':None})
self.assert_(dictlike.fromkeys('a').__class__ is dictlike)
self.assert_(dictlike().fromkeys('a').__class__ is dictlike)
# FIXME: the following won't work with UserDict, because it's an old style class
# self.assert_(type(dictlike.fromkeys('a')) is dictlike)
class mydict(self.type2test):
def __new__(cls):
return UserDict.UserDict()
ud = mydict.fromkeys('ab')
self.assertEqual(ud, {'a':None, 'b':None})
# FIXME: the following won't work with UserDict, because it's an old style class
# self.assert_(isinstance(ud, UserDict.UserDict))
self.assertRaises(TypeError, dict.fromkeys)
class Exc(Exception): pass
class baddict1(self.type2test):
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, self.type2test.fromkeys, BadSeq())
class baddict2(self.type2test):
def __setitem__(self, key, value):
raise Exc()
self.assertRaises(Exc, baddict2.fromkeys, [1])
def test_copy(self):
d = self._full_mapping({1:1, 2:2, 3:3})
self.assertEqual(d.copy(), {1:1, 2:2, 3:3})
d = self._empty_mapping()
self.assertEqual(d.copy(), d)
self.assert_(isinstance(d.copy(), d.__class__))
self.assertRaises(TypeError, d.copy, None)
def test_get(self):
BasicTestMappingProtocol.test_get(self)
d = self._empty_mapping()
self.assert_(d.get('c') is None)
self.assertEqual(d.get('c', 3), 3)
d = self._full_mapping({'a' : 1, 'b' : 2})
self.assert_(d.get('c') is None)
self.assertEqual(d.get('c', 3), 3)
self.assertEqual(d.get('a'), 1)
self.assertEqual(d.get('a', 3), 1)
def test_setdefault(self):
BasicTestMappingProtocol.test_setdefault(self)
d = self._empty_mapping()
self.assert_(d.setdefault('key0') is None)
d.setdefault('key0', [])
self.assert_(d.setdefault('key0') is None)
d.setdefault('key', []).append(3)
self.assertEqual(d['key'][0], 3)
d.setdefault('key', []).append(4)
self.assertEqual(len(d['key']), 2)
def test_popitem(self):
BasicTestMappingProtocol.test_popitem(self)
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 = self._empty_mapping()
b = self._empty_mapping()
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.assert_(not(copymode < 0 and ta != tb))
self.assert_(not a)
self.assert_(not b)
def test_pop(self):
BasicTestMappingProtocol.test_pop(self)
# Tests for pop with specified key
d = self._empty_mapping()
k, v = 'abc', 'def'
# verify longs/ints get same value when key > 32 bits (for 64-bit archs)
# see SF bug #689659
x = 4503599627370496
y = 4503599627370496
h = self._full_mapping({x: 'anything', y: 'something else'})
self.assertEqual(h[x], h[y])
self.assertEqual(d.pop(k, v), v)
d[k] = v
self.assertEqual(d.pop(k, 1), v)
class TestHashMappingProtocol(TestMappingProtocol):
def test_getitem(self):
TestMappingProtocol.test_getitem(self)
class Exc(Exception): pass
class BadEq(object):
def __eq__(self, other):
raise Exc()
def __hash__(self):
return 24
d = self._empty_mapping()
d[BadEq()] = 42
self.assertRaises(KeyError, d.__getitem__, 23)
class BadHash(object):
fail = False
def __hash__(self):
if self.fail:
raise Exc()
else:
return 42
d = self._empty_mapping()
x = BadHash()
d[x] = 42
x.fail = True
self.assertRaises(Exc, d.__getitem__, x)
def test_fromkeys(self):
TestMappingProtocol.test_fromkeys(self)
class mydict(self.type2test):
def __new__(cls):
return UserDict.UserDict()
ud = mydict.fromkeys('ab')
self.assertEqual(ud, {'a':None, 'b':None})
self.assert_(isinstance(ud, UserDict.UserDict))
def test_pop(self):
TestMappingProtocol.test_pop(self)
class Exc(Exception): pass
class BadHash(object):
fail = False
def __hash__(self):
if self.fail:
raise Exc()
else:
return 42
d = self._empty_mapping()
x = BadHash()
d[x] = 42
x.fail = True
self.assertRaises(Exc, d.pop, x)
def test_mutatingiteration(self):
d = self._empty_mapping()
d[1] = 1
try:
for i in d:
d[i+1] = 1
except RuntimeError:
pass
else:
self.fail("changing dict size during iteration doesn't raise Error")
def test_repr(self):
d = self._empty_mapping()
self.assertEqual(repr(d), '{}')
d[1] = 2
self.assertEqual(repr(d), '{1: 2}')
d = self._empty_mapping()
d[1] = d
self.assertEqual(repr(d), '{1: {...}}')
class Exc(Exception): pass
class BadRepr(object):
def __repr__(self):
raise Exc()
d = self._full_mapping({1: BadRepr()})
self.assertRaises(Exc, repr, d)
Restructure comparison dramatically. There is no longer a default *ordering* between objects; there is only a default equality test (defined by an object being equal to itself only). Read the comment in object.c. The current implementation never uses a three-way comparison to compute a rich comparison, but it does use a rich comparison to compute a three-way comparison. I'm not quite done ripping out all the calls to PyObject_Compare/Cmp, or replacing tp_compare implementations with tp_richcompare implementations; but much of that has happened (to make most unit tests pass). The following tests still fail, because I need help deciding or understanding: test_codeop -- depends on comparing code objects test_datetime -- need Tim Peters' opinion test_marshal -- depends on comparing code objects test_mutants -- need help understanding it The problem with test_codeop and test_marshal is this: these tests compare two different code objects and expect them to be equal. Is that still a feature we'd like to support? I've temporarily removed the comparison and hash code from code objects, so they use the default (equality by pointer only) comparison. For the other two tests, run them to see for yourself. (There may be more failing test with "-u all".) A general problem with getting lots of these tests to pass is the reality that for object types that have a natural total ordering, implementing __cmp__ is much more convenient than implementing __eq__, __ne__, __lt__, and so on. Should we go back to allowing __cmp__ to provide a total ordering? Should we provide some other way to implement rich comparison with a single method override? Alex proposed a __key__() method; I've considered a __richcmp__() method. Or perhaps __cmp__() just shouldn't be killed off...
2006-08-23 21:41:19 -03:00
def test_eq(self):
self.assertEqual(self._empty_mapping(), self._empty_mapping())
self.assertEqual(self._full_mapping({1: 2}),
self._full_mapping({1: 2}))
class Exc(Exception): pass
class BadCmp(object):
def __eq__(self, other):
raise Exc()
def __hash__(self):
Restructure comparison dramatically. There is no longer a default *ordering* between objects; there is only a default equality test (defined by an object being equal to itself only). Read the comment in object.c. The current implementation never uses a three-way comparison to compute a rich comparison, but it does use a rich comparison to compute a three-way comparison. I'm not quite done ripping out all the calls to PyObject_Compare/Cmp, or replacing tp_compare implementations with tp_richcompare implementations; but much of that has happened (to make most unit tests pass). The following tests still fail, because I need help deciding or understanding: test_codeop -- depends on comparing code objects test_datetime -- need Tim Peters' opinion test_marshal -- depends on comparing code objects test_mutants -- need help understanding it The problem with test_codeop and test_marshal is this: these tests compare two different code objects and expect them to be equal. Is that still a feature we'd like to support? I've temporarily removed the comparison and hash code from code objects, so they use the default (equality by pointer only) comparison. For the other two tests, run them to see for yourself. (There may be more failing test with "-u all".) A general problem with getting lots of these tests to pass is the reality that for object types that have a natural total ordering, implementing __cmp__ is much more convenient than implementing __eq__, __ne__, __lt__, and so on. Should we go back to allowing __cmp__ to provide a total ordering? Should we provide some other way to implement rich comparison with a single method override? Alex proposed a __key__() method; I've considered a __richcmp__() method. Or perhaps __cmp__() just shouldn't be killed off...
2006-08-23 21:41:19 -03:00
return 1
d1 = self._full_mapping({BadCmp(): 1})
d2 = self._full_mapping({1: 1})
Restructure comparison dramatically. There is no longer a default *ordering* between objects; there is only a default equality test (defined by an object being equal to itself only). Read the comment in object.c. The current implementation never uses a three-way comparison to compute a rich comparison, but it does use a rich comparison to compute a three-way comparison. I'm not quite done ripping out all the calls to PyObject_Compare/Cmp, or replacing tp_compare implementations with tp_richcompare implementations; but much of that has happened (to make most unit tests pass). The following tests still fail, because I need help deciding or understanding: test_codeop -- depends on comparing code objects test_datetime -- need Tim Peters' opinion test_marshal -- depends on comparing code objects test_mutants -- need help understanding it The problem with test_codeop and test_marshal is this: these tests compare two different code objects and expect them to be equal. Is that still a feature we'd like to support? I've temporarily removed the comparison and hash code from code objects, so they use the default (equality by pointer only) comparison. For the other two tests, run them to see for yourself. (There may be more failing test with "-u all".) A general problem with getting lots of these tests to pass is the reality that for object types that have a natural total ordering, implementing __cmp__ is much more convenient than implementing __eq__, __ne__, __lt__, and so on. Should we go back to allowing __cmp__ to provide a total ordering? Should we provide some other way to implement rich comparison with a single method override? Alex proposed a __key__() method; I've considered a __richcmp__() method. Or perhaps __cmp__() just shouldn't be killed off...
2006-08-23 21:41:19 -03:00
self.assertRaises(Exc, lambda: BadCmp()==1)
self.assertRaises(Exc, lambda: d1==d2)
def test_setdefault(self):
TestMappingProtocol.test_setdefault(self)
class Exc(Exception): pass
class BadHash(object):
fail = False
def __hash__(self):
if self.fail:
raise Exc()
else:
return 42
d = self._empty_mapping()
x = BadHash()
d[x] = 42
x.fail = True
self.assertRaises(Exc, d.setdefault, x, [])