Lib/test/test_hash.py

# test the invariant that
#   iff a==b then hash(a)==hash(b)
#
# Also test that hash implementations are inherited as expected

import datetime
import os
import sys
import unittest
from test import support
from test.script_helper import assert_python_ok
from collections import Hashable

IS_64BIT = sys.maxsize > 2**32


class HashEqualityTestCase(unittest.TestCase):

    def same_hash(self, *objlist):
        # Hash each object given and fail if
        # the hash values are not all the same.
        hashed = list(map(hash, objlist))
        for h in hashed[1:]:
            if h != hashed[0]:
                self.fail("hashed values differ: %r" % (objlist,))

    def test_numeric_literals(self):
        self.same_hash(1, 1, 1.0, 1.0+0.0j)
        self.same_hash(0, 0.0, 0.0+0.0j)
        self.same_hash(-1, -1.0, -1.0+0.0j)
        self.same_hash(-2, -2.0, -2.0+0.0j)

    def test_coerced_integers(self):
        self.same_hash(int(1), int(1), float(1), complex(1),
                       int('1'), float('1.0'))
        self.same_hash(int(-2**31), float(-2**31))
        self.same_hash(int(1-2**31), float(1-2**31))
        self.same_hash(int(2**31-1), float(2**31-1))
        # for 64-bit platforms
        self.same_hash(int(2**31), float(2**31))
        self.same_hash(int(-2**63), float(-2**63))
        self.same_hash(int(2**63), float(2**63))

    def test_coerced_floats(self):
        self.same_hash(int(1.23e300), float(1.23e300))
        self.same_hash(float(0.5), complex(0.5, 0.0))

    def test_unaligned_buffers(self):
        # The hash function for bytes-like objects shouldn't have
        # alignment-dependent results (example in issue #16427).
        b = b"123456789abcdefghijklmnopqrstuvwxyz" * 128
        for i in range(16):
            for j in range(16):
                aligned = b[i:128+j]
                unaligned = memoryview(b)[i:128+j]
                self.assertEqual(hash(aligned), hash(unaligned))


_default_hash = object.__hash__
class DefaultHash(object): pass

_FIXED_HASH_VALUE = 42
class FixedHash(object):
    def __hash__(self):
        return _FIXED_HASH_VALUE

class OnlyEquality(object):
    def __eq__(self, other):
        return self is other

class OnlyInequality(object):
    def __ne__(self, other):
        return self is not other

class InheritedHashWithEquality(FixedHash, OnlyEquality): pass
class InheritedHashWithInequality(FixedHash, OnlyInequality): pass

class NoHash(object):
    __hash__ = None

class HashInheritanceTestCase(unittest.TestCase):
    default_expected = [object(),
                        DefaultHash(),
                        OnlyInequality(),
                       ]
    fixed_expected = [FixedHash(),
                      InheritedHashWithEquality(),
                      InheritedHashWithInequality(),
                      ]
    error_expected = [NoHash(),
                      OnlyEquality(),
                      ]

    def test_default_hash(self):
        for obj in self.default_expected:
            self.assertEqual(hash(obj), _default_hash(obj))

    def test_fixed_hash(self):
        for obj in self.fixed_expected:
            self.assertEqual(hash(obj), _FIXED_HASH_VALUE)

    def test_error_hash(self):
        for obj in self.error_expected:
            self.assertRaises(TypeError, hash, obj)

    def test_hashable(self):
        objects = (self.default_expected +
                   self.fixed_expected)
        for obj in objects:
            self.assertIsInstance(obj, Hashable)

    def test_not_hashable(self):
        for obj in self.error_expected:
            self.assertNotIsInstance(obj, Hashable)


# Issue #4701: Check that some builtin types are correctly hashable
class DefaultIterSeq(object):
    seq = range(10)
    def __len__(self):
        return len(self.seq)
    def __getitem__(self, index):
        return self.seq[index]

class HashBuiltinsTestCase(unittest.TestCase):
    hashes_to_check = [enumerate(range(10)),
                       iter(DefaultIterSeq()),
                       iter(lambda: 0, 0),
                      ]

    def test_hashes(self):
        _default_hash = object.__hash__
        for obj in self.hashes_to_check:
            self.assertEqual(hash(obj), _default_hash(obj))

class HashRandomizationTests(unittest.TestCase):

    # Each subclass should define a field "repr_", containing the repr() of
    # an object to be tested

    def get_hash_command(self, repr_):
        return 'print(hash(%s))' % repr_

    def get_hash(self, repr_, seed=None):
        env = os.environ.copy()
        env['__cleanenv'] = True  # signal to assert_python not to do a copy
                                  # of os.environ on its own
        if seed is not None:
            env['PYTHONHASHSEED'] = str(seed)
        else:
            env.pop('PYTHONHASHSEED', None)
        out = assert_python_ok(
            '-c', self.get_hash_command(repr_),
            **env)
        stdout = out[1].strip()
        return int(stdout)

    def test_randomized_hash(self):
        # two runs should return different hashes
        run1 = self.get_hash(self.repr_, seed='random')
        run2 = self.get_hash(self.repr_, seed='random')
        self.assertNotEqual(run1, run2)

class StringlikeHashRandomizationTests(HashRandomizationTests):
    def test_null_hash(self):
        # PYTHONHASHSEED=0 disables the randomized hash
        if IS_64BIT:
            known_hash_of_obj = 1453079729188098211
        else:
            known_hash_of_obj = -1600925533

        # Randomization is enabled by default:
        self.assertNotEqual(self.get_hash(self.repr_), known_hash_of_obj)

        # It can also be disabled by setting the seed to 0:
        self.assertEqual(self.get_hash(self.repr_, seed=0), known_hash_of_obj)

    def test_fixed_hash(self):
        # test a fixed seed for the randomized hash
        # Note that all types share the same values:
        if IS_64BIT:
            if sys.byteorder == 'little':
                h = -4410911502303878509
            else:
                h = -3570150969479994130
        else:
            if sys.byteorder == 'little':
                h = -206076799
            else:
                h = -1024014457
        self.assertEqual(self.get_hash(self.repr_, seed=42), h)

class StrHashRandomizationTests(StringlikeHashRandomizationTests):
    repr_ = repr('abc')

    def test_empty_string(self):
        self.assertEqual(hash(""), 0)

class BytesHashRandomizationTests(StringlikeHashRandomizationTests):
    repr_ = repr(b'abc')

    def test_empty_string(self):
        self.assertEqual(hash(b""), 0)

class MemoryviewHashRandomizationTests(StringlikeHashRandomizationTests):
    repr_ = "memoryview(b'abc')"

    def test_empty_string(self):
        self.assertEqual(hash(memoryview(b"")), 0)

class DatetimeTests(HashRandomizationTests):
    def get_hash_command(self, repr_):
        return 'import datetime; print(hash(%s))' % repr_

class DatetimeDateTests(DatetimeTests):
    repr_ = repr(datetime.date(1066, 10, 14))

class DatetimeDatetimeTests(DatetimeTests):
    repr_ = repr(datetime.datetime(1, 2, 3, 4, 5, 6, 7))

class DatetimeTimeTests(DatetimeTests):
    repr_ = repr(datetime.time(0))


def test_main():
    support.run_unittest(HashEqualityTestCase,
                         HashInheritanceTestCase,
                         HashBuiltinsTestCase,
                         StrHashRandomizationTests,
                         BytesHashRandomizationTests,
                         MemoryviewHashRandomizationTests,
                         DatetimeDateTests,
                         DatetimeDatetimeTests,
                         DatetimeTimeTests)


if __name__ == "__main__":
    test_main()