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author | Raymond Hettinger <python@rcn.com> | 2003-11-12 14:32:26 (GMT) |
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committer | Raymond Hettinger <python@rcn.com> | 2003-11-12 14:32:26 (GMT) |
commit | ad983e79d6f215235d205245c2599620e33cf719 (patch) | |
tree | f6dcc71e1d751c52d72b095806143a692af7d2b0 /Lib/test/test_itertools.py | |
parent | 767126d7b979020585da0d2b35bda5aae7a40d30 (diff) | |
download | cpython-ad983e79d6f215235d205245c2599620e33cf719.zip cpython-ad983e79d6f215235d205245c2599620e33cf719.tar.gz cpython-ad983e79d6f215235d205245c2599620e33cf719.tar.bz2 |
Improve the implementation of itertools.tee().
Formerly, underlying queue was implemented in terms of two lists. The
new queue is a series of singly-linked fixed length lists.
The new implementation runs much faster, supports multi-way tees, and
allows tees of tees without additional memory costs.
The root ideas for this structure were contributed by Andrew Koenig
and Guido van Rossum.
Diffstat (limited to 'Lib/test/test_itertools.py')
-rw-r--r-- | Lib/test/test_itertools.py | 55 |
1 files changed, 31 insertions, 24 deletions
diff --git a/Lib/test/test_itertools.py b/Lib/test/test_itertools.py index 07219a9..543acc1 100644 --- a/Lib/test/test_itertools.py +++ b/Lib/test/test_itertools.py @@ -200,7 +200,7 @@ class TestBasicOps(unittest.TestCase): self.assertRaises(ValueError, dropwhile(errfunc, [(4,5)]).next) def test_tee(self): - n = 100 + n = 200 def irange(n): for i in xrange(n): yield i @@ -217,16 +217,16 @@ class TestBasicOps(unittest.TestCase): self.assertEqual(list(b), range(n)) a, b = tee(irange(n)) # test dealloc of leading iterator - self.assertEqual(a.next(), 0) - self.assertEqual(a.next(), 1) + for i in xrange(100): + self.assertEqual(a.next(), i) del a self.assertEqual(list(b), range(n)) a, b = tee(irange(n)) # test dealloc of trailing iterator - self.assertEqual(a.next(), 0) - self.assertEqual(a.next(), 1) + for i in xrange(100): + self.assertEqual(a.next(), i) del b - self.assertEqual(list(a), range(2, n)) + self.assertEqual(list(a), range(100, n)) for j in xrange(5): # test randomly interleaved order = [0]*n + [1]*n @@ -239,21 +239,31 @@ class TestBasicOps(unittest.TestCase): self.assertEqual(lists[0], range(n)) self.assertEqual(lists[1], range(n)) + # test argument format checking self.assertRaises(TypeError, tee) self.assertRaises(TypeError, tee, 3) self.assertRaises(TypeError, tee, [1,2], 'x') + self.assertRaises(TypeError, tee, [1,2], 3, 'x') - try: - class A(tee): pass - except TypeError: - pass - else: - self.fail("tee constructor should not be subclassable") + # tee object should be instantiable + a, b = tee('abc') + c = type(a)('def') + self.assertEqual(list(c), list('def')) + + # test long-lagged and multi-way split + a, b, c = tee(xrange(2000), 3) + for i in xrange(100): + self.assertEqual(a.next(), i) + self.assertEqual(list(b), range(2000)) + self.assertEqual([c.next(), c.next()], range(2)) + self.assertEqual(list(a), range(100,2000)) + self.assertEqual(list(c), range(2,2000)) + + # tee pass-through to copyable iterator + a, b = tee('abc') + c, d = tee(a) + self.assert_(a is c) - # tee_iterator should not be instantiable - a, b = tee(xrange(10)) - self.assertRaises(TypeError, type(a)) - self.assert_(a is iter(a)) # tee_iterator should support __iter__ def test_StopIteration(self): self.assertRaises(StopIteration, izip().next) @@ -317,13 +327,6 @@ class TestGC(unittest.TestCase): a = [] self.makecycle(starmap(lambda *t: t, [(a,a)]*2), a) - def test_tee(self): - a = [] - p, q = t = tee([a]*2) - a += [a, p, q, t] - p.next() - del a, p, q, t - def R(seqn): 'Regular generator' for i in seqn: @@ -626,7 +629,11 @@ Samuele >>> def pairwise(iterable): ... "s -> (s0,s1), (s1,s2), (s2, s3), ..." ... a, b = tee(iterable) -... return izip(a, islice(b, 1, None)) +... try: +... b.next() +... except StopIteration: +... pass +... return izip(a, b) This is not part of the examples but it tests to make sure the definitions perform as purported. |