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import unittest
from test import test_support, seq_tests
class TupleTest(seq_tests.CommonTest):
type2test = tuple
def test_constructors(self):
super(TupleTest, self).test_len()
# calling built-in types without argument must return empty
self.assertEqual(tuple(), ())
def test_truth(self):
super(TupleTest, self).test_truth()
self.assert_(not ())
self.assert_((42, ))
def test_len(self):
super(TupleTest, self).test_len()
self.assertEqual(len(()), 0)
self.assertEqual(len((0,)), 1)
self.assertEqual(len((0, 1, 2)), 3)
def test_iadd(self):
super(TupleTest, self).test_iadd()
u = (0, 1)
u2 = u
u += (2, 3)
self.assert_(u is not u2)
def test_imul(self):
super(TupleTest, self).test_imul()
u = (0, 1)
u2 = u
u *= 3
self.assert_(u is not u2)
def test_tupleresizebug(self):
# Check that a specific bug in _PyTuple_Resize() is squashed.
def f():
for i in range(1000):
yield i
self.assertEqual(list(tuple(f())), range(1000))
def test_hash(self):
# See SF bug 942952: Weakness in tuple hash
# The hash should:
# be non-commutative
# should spread-out closely spaced values
# should not exhibit cancellation in tuples like (x,(x,y))
# should be distinct from element hashes: hash(x)!=hash((x,))
# This test exercises those cases.
# For a pure random hash and N=50, the expected number of occupied
# buckets when tossing 252,600 balls into 2**32 buckets
# is 252,592.6, or about 7.4 expected collisions. The
# standard deviation is 2.73. On a box with 64-bit hash
# codes, no collisions are expected. Here we accept no
# more than 15 collisions. Any worse and the hash function
# is sorely suspect.
N=50
base = range(N)
xp = [(i, j) for i in base for j in base]
inps = base + [(i, j) for i in base for j in xp] + \
[(i, j) for i in xp for j in base] + xp + zip(base)
collisions = len(inps) - len(set(map(hash, inps)))
self.assert_(collisions <= 15)
def test_main():
test_support.run_unittest(TupleTest)
if __name__=="__main__":
test_main()
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