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authorRaymond Hettinger <python@rcn.com>2003-11-12 14:32:26 (GMT)
committerRaymond Hettinger <python@rcn.com>2003-11-12 14:32:26 (GMT)
commitad983e79d6f215235d205245c2599620e33cf719 (patch)
treef6dcc71e1d751c52d72b095806143a692af7d2b0 /Lib/test/test_itertools.py
parent767126d7b979020585da0d2b35bda5aae7a40d30 (diff)
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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.py55
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.