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
   6 import unittest
   7 from test import support
   8 from collections import Hashable
   9
  10
  11 class 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 = list(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, 1, 1.0, 1.0+0.0j)
  23         self.same_hash(0, 0.0, 0.0+0.0j)
  24         self.same_hash(-1, -1.0, -1.0+0.0j)
  25         self.same_hash(-2, -2.0, -2.0+0.0j)
  26
  27     def test_coerced_integers(self):
  28         self.same_hash(int(1), int(1), float(1), complex(1),
  29                        int('1'), float('1.0'))
  30         self.same_hash(int(-2**31), float(-2**31))
  31         self.same_hash(int(1-2**31), float(1-2**31))
  32         self.same_hash(int(2**31-1), float(2**31-1))
  33         # for 64-bit platforms
  34         self.same_hash(int(2**31), float(2**31))
  35         self.same_hash(int(-2**63), float(-2**63))
  36         self.same_hash(int(2**63), float(2**63))
  37
  38     def test_coerced_floats(self):
  39         self.same_hash(int(1.23e300), float(1.23e300))
  40         self.same_hash(float(0.5), complex(0.5, 0.0))
  41
  42
  43 _default_hash = object.__hash__
  44 class DefaultHash(object): pass
  45
  46 _FIXED_HASH_VALUE = 42
  47 class FixedHash(object):
  48     def __hash__(self):
  49         return _FIXED_HASH_VALUE
  50
  51 class OnlyEquality(object):
  52     def __eq__(self, other):
  53         return self is other
  54
  55 class OnlyInequality(object):
  56     def __ne__(self, other):
  57         return self is not other
  58
  59 class InheritedHashWithEquality(FixedHash, OnlyEquality): pass
  60 class InheritedHashWithInequality(FixedHash, OnlyInequality): pass
  61
  62 class NoHash(object):
  63     __hash__ = None
  64
  65 class HashInheritanceTestCase(unittest.TestCase):
  66     default_expected = [object(),
  67                         DefaultHash(),
  68                         OnlyInequality(),
  69                        ]
  70     fixed_expected = [FixedHash(),
  71                       InheritedHashWithEquality(),
  72                       InheritedHashWithInequality(),
  73                       ]
  74     error_expected = [NoHash(),
  75                       OnlyEquality(),
  76                       ]
  77
  78     def test_default_hash(self):
  79         for obj in self.default_expected:
  80             self.assertEqual(hash(obj), _default_hash(obj))
  81
  82     def test_fixed_hash(self):
  83         for obj in self.fixed_expected:
  84             self.assertEqual(hash(obj), _FIXED_HASH_VALUE)
  85
  86     def test_error_hash(self):
  87         for obj in self.error_expected:
  88             self.assertRaises(TypeError, hash, obj)
  89
  90     def test_hashable(self):
  91         objects = (self.default_expected +
  92                    self.fixed_expected)
  93         for obj in objects:
  94             self.assert_(isinstance(obj, Hashable), repr(obj))
  95
  96     def test_not_hashable(self):
  97         for obj in self.error_expected:
  98             self.assertFalse(isinstance(obj, Hashable), repr(obj))
  99
 100
 101 # Issue #4701: Check that some builtin types are correctly hashable
 102 class DefaultIterSeq(object):
 103     seq = range(10)
 104     def __len__(self):
 105         return len(self.seq)
 106     def __getitem__(self, index):
 107         return self.seq[index]
 108
 109 class HashBuiltinsTestCase(unittest.TestCase):
 110     hashes_to_check = [range(10),
 111                        enumerate(range(10)),
 112                        iter(DefaultIterSeq()),
 113                        iter(lambda: 0, 0),
 114                       ]
 115
 116     def test_hashes(self):
 117         _default_hash = object.__hash__
 118         for obj in self.hashes_to_check:
 119             self.assertEqual(hash(obj), _default_hash(obj))
 120
 121 def test_main():
 122     support.run_unittest(HashEqualityTestCase,
 123                               HashInheritanceTestCase,
 124                               HashBuiltinsTestCase)
 125
 126
 127 if __name__ == "__main__":
 128     test_main()