1 import unittest

     2 from test import test_support, seq_tests

     3 

     4 class TupleTest(seq_tests.CommonTest):

     5     type2test = tuple

     6 

     7     def test_constructors(self):

     8         super(TupleTest, self).test_len()

     9         # calling built-in types without argument must return empty

    10         self.assertEqual(tuple(), ())

    11 

    12     def test_truth(self):

    13         super(TupleTest, self).test_truth()

    14         self.assert_(not ())

    15         self.assert_((42, ))

    16 

    17     def test_len(self):

    18         super(TupleTest, self).test_len()

    19         self.assertEqual(len(()), 0)

    20         self.assertEqual(len((0,)), 1)

    21         self.assertEqual(len((0, 1, 2)), 3)

    22 

    23     def test_iadd(self):

    24         super(TupleTest, self).test_iadd()

    25         u = (0, 1)

    26         u2 = u

    27         u += (2, 3)

    28         self.assert_(u is not u2)

    29 

    30     def test_imul(self):

    31         super(TupleTest, self).test_imul()

    32         u = (0, 1)

    33         u2 = u

    34         u *= 3

    35         self.assert_(u is not u2)

    36 

    37     def test_tupleresizebug(self):

    38         # Check that a specific bug in _PyTuple_Resize() is squashed.

    39         def f():

    40             for i in range(1000):

    41                 yield i

    42         self.assertEqual(list(tuple(f())), range(1000))

    43 

    44     def test_hash(self):

    45         # See SF bug 942952:  Weakness in tuple hash

    46         # The hash should:

    47         #      be non-commutative

    48         #      should spread-out closely spaced values

    49         #      should not exhibit cancellation in tuples like (x,(x,y))

    50         #      should be distinct from element hashes:  hash(x)!=hash((x,))

    51         # This test exercises those cases.

    52         # For a pure random hash and N=50, the expected number of occupied

    53         #      buckets when tossing 252,600 balls into 2**32 buckets

    54         #      is 252,592.6, or about 7.4 expected collisions.  The

    55         #      standard deviation is 2.73.  On a box with 64-bit hash

    56         #      codes, no collisions are expected.  Here we accept no

    57         #      more than 15 collisions.  Any worse and the hash function

    58         #      is sorely suspect.

    59 

    60         N=50

    61         base = range(N)

    62         xp = [(i, j) for i in base for j in base]

    63         inps = base + [(i, j) for i in base for j in xp] + \

    64                      [(i, j) for i in xp for j in base] + xp + zip(base)

    65         collisions = len(inps) - len(set(map(hash, inps)))

    66         self.assert_(collisions <= 15)

    67 

    68     def test_repr(self):

    69         l0 = tuple()

    70         l2 = (0, 1, 2)

    71         a0 = self.type2test(l0)

    72         a2 = self.type2test(l2)

    73 

    74         self.assertEqual(str(a0), repr(l0))

    75         self.assertEqual(str(a2), repr(l2))

    76         self.assertEqual(repr(a0), "()")

    77         self.assertEqual(repr(a2), "(0, 1, 2)")

    78 

    79 def test_main():

    80     test_support.run_unittest(TupleTest)

    81 

    82 if __name__=="__main__":

    83     test_main()