/Lib/test/test_hash.py

  1# test the invariant that
  2#   iff a==b then hash(a)==hash(b)
  3#
  4# Also test that hash implementations are inherited as expected
  5
  6import unittest
  7from test import test_support
  8from collections import Hashable
  9
 10
 11class HashEqualityTestCase(unittest.TestCase):
 12
 13    def same_hash(self, *objlist):
 14        # Hash each object given and fail if
 15        # the hash values are not all the same.
 16        hashed = map(hash, objlist)
 17        for h in hashed[1:]:
 18            if h != hashed[0]:
 19                self.fail("hashed values differ: %r" % (objlist,))
 20
 21    def test_numeric_literals(self):
 22        self.same_hash(1, 1L, 1.0, 1.0+0.0j)
 23        self.same_hash(0, 0L, 0.0, 0.0+0.0j)
 24        self.same_hash(-1, -1L, -1.0, -1.0+0.0j)
 25        self.same_hash(-2, -2L, -2.0, -2.0+0.0j)
 26
 27    def test_coerced_integers(self):
 28        self.same_hash(int(1), long(1), float(1), complex(1),
 29                       int('1'), float('1.0'))
 30        self.same_hash(int(-2**31), long(-2**31), float(-2**31))
 31        self.same_hash(int(1-2**31), long(1-2**31), float(1-2**31))
 32        self.same_hash(int(2**31-1), long(2**31-1), float(2**31-1))
 33        # for 64-bit platforms
 34        self.same_hash(int(2**31), long(2**31), float(2**31))
 35        self.same_hash(int(-2**63), long(-2**63), float(-2**63))
 36        self.same_hash(int(1-2**63), long(1-2**63))
 37        self.same_hash(int(2**63-1), long(2**63-1))
 38
 39    def test_coerced_floats(self):
 40        self.same_hash(long(1.23e300), float(1.23e300))
 41        self.same_hash(float(0.5), complex(0.5, 0.0))
 42
 43
 44_default_hash = object.__hash__
 45class DefaultHash(object): pass
 46
 47_FIXED_HASH_VALUE = 42
 48class FixedHash(object):
 49    def __hash__(self):
 50        return _FIXED_HASH_VALUE
 51
 52class OnlyEquality(object):
 53    def __eq__(self, other):
 54        return self is other
 55    # Trick to suppress Py3k warning in 2.x
 56    __hash__ = None
 57del OnlyEquality.__hash__
 58
 59class OnlyInequality(object):
 60    def __ne__(self, other):
 61        return self is not other
 62
 63class OnlyCmp(object):
 64    def __cmp__(self, other):
 65        return cmp(id(self), id(other))
 66    # Trick to suppress Py3k warning in 2.x
 67    __hash__ = None
 68del OnlyCmp.__hash__
 69
 70class InheritedHashWithEquality(FixedHash, OnlyEquality): pass
 71class InheritedHashWithInequality(FixedHash, OnlyInequality): pass
 72class InheritedHashWithCmp(FixedHash, OnlyCmp): pass
 73
 74class NoHash(object):
 75    __hash__ = None
 76
 77class HashInheritanceTestCase(unittest.TestCase):
 78    default_expected = [object(),
 79                        DefaultHash(),
 80                        OnlyEquality(),
 81                        OnlyInequality(),
 82                        OnlyCmp(),
 83                       ]
 84    fixed_expected = [FixedHash(),
 85                      InheritedHashWithEquality(),
 86                      InheritedHashWithInequality(),
 87                      InheritedHashWithCmp(),
 88                      ]
 89    error_expected = [NoHash()]
 90
 91    def test_default_hash(self):
 92        for obj in self.default_expected:
 93            self.assertEqual(hash(obj), _default_hash(obj))
 94
 95    def test_fixed_hash(self):
 96        for obj in self.fixed_expected:
 97            self.assertEqual(hash(obj), _FIXED_HASH_VALUE)
 98
 99    def test_error_hash(self):
100        for obj in self.error_expected:
101            self.assertRaises(TypeError, hash, obj)
102
103    def test_hashable(self):
104        objects = (self.default_expected +
105                   self.fixed_expected)
106        for obj in objects:
107            self.assert_(isinstance(obj, Hashable), repr(obj))
108
109    def test_not_hashable(self):
110        for obj in self.error_expected:
111            self.assertFalse(isinstance(obj, Hashable), repr(obj))
112
113
114# Issue #4701: Check that some builtin types are correctly hashable
115#  (This test only used to fail in Python 3.0, but has been included
116#   in 2.x along with the lazy call to PyType_Ready in PyObject_Hash)
117class DefaultIterSeq(object):
118    seq = range(10)
119    def __len__(self):
120        return len(self.seq)
121    def __getitem__(self, index):
122        return self.seq[index]
123
124class HashBuiltinsTestCase(unittest.TestCase):
125    hashes_to_check = [xrange(10),
126                       enumerate(xrange(10)),
127                       iter(DefaultIterSeq()),
128                       iter(lambda: 0, 0),
129                      ]
130
131    def test_hashes(self):
132        _default_hash = object.__hash__
133        for obj in self.hashes_to_check:
134            self.assertEqual(hash(obj), _default_hash(obj))
135
136def test_main():
137    test_support.run_unittest(HashEqualityTestCase,
138                              HashInheritanceTestCase,
139                              HashBuiltinsTestCase)
140
141
142if __name__ == "__main__":
143    test_main()