Commits

4kir4 committed 77c0e63

copy test_itertools.py to skip CPython specific tests

  • Participants
  • Parent commits 7b216ec

Comments (0)

Files changed (1)

File lib-python/modified-2.7.0/test/test_itertools.py

+import unittest
+from test import test_support
+from itertools import *
+from weakref import proxy
+from decimal import Decimal
+from fractions import Fraction
+import sys
+import operator
+import random
+import copy
+import pickle
+from functools import reduce
+maxsize = test_support.MAX_Py_ssize_t
+minsize = -maxsize-1
+
+def onearg(x):
+    'Test function of one argument'
+    return 2*x
+
+def errfunc(*args):
+    'Test function that raises an error'
+    raise ValueError
+
+def gen3():
+    'Non-restartable source sequence'
+    for i in (0, 1, 2):
+        yield i
+
+def isEven(x):
+    'Test predicate'
+    return x%2==0
+
+def isOdd(x):
+    'Test predicate'
+    return x%2==1
+
+class StopNow:
+    'Class emulating an empty iterable.'
+    def __iter__(self):
+        return self
+    def next(self):
+        raise StopIteration
+
+def take(n, seq):
+    'Convenience function for partially consuming a long of infinite iterable'
+    return list(islice(seq, n))
+
+def prod(iterable):
+    return reduce(operator.mul, iterable, 1)
+
+def fact(n):
+    'Factorial'
+    return prod(range(1, n+1))
+
+class TestBasicOps(unittest.TestCase):
+    def test_chain(self):
+
+        def chain2(*iterables):
+            'Pure python version in the docs'
+            for it in iterables:
+                for element in it:
+                    yield element
+
+        for c in (chain, chain2):
+            self.assertEqual(list(c('abc', 'def')), list('abcdef'))
+            self.assertEqual(list(c('abc')), list('abc'))
+            self.assertEqual(list(c('')), [])
+            self.assertEqual(take(4, c('abc', 'def')), list('abcd'))
+            self.assertRaises(TypeError, list,c(2, 3))
+
+    def test_chain_from_iterable(self):
+        self.assertEqual(list(chain.from_iterable(['abc', 'def'])), list('abcdef'))
+        self.assertEqual(list(chain.from_iterable(['abc'])), list('abc'))
+        self.assertEqual(list(chain.from_iterable([''])), [])
+        self.assertEqual(take(4, chain.from_iterable(['abc', 'def'])), list('abcd'))
+        self.assertRaises(TypeError, list, chain.from_iterable([2, 3]))
+
+    def test_combinations(self):
+        self.assertRaises(TypeError, combinations, 'abc')       # missing r argument
+        self.assertRaises(TypeError, combinations, 'abc', 2, 1) # too many arguments
+        self.assertRaises(TypeError, combinations, None)        # pool is not iterable
+        self.assertRaises(ValueError, combinations, 'abc', -2)  # r is negative
+        self.assertEqual(list(combinations('abc', 32)), [])     # r > n
+        self.assertEqual(list(combinations(range(4), 3)),
+                                           [(0,1,2), (0,1,3), (0,2,3), (1,2,3)])
+
+        def combinations1(iterable, r):
+            'Pure python version shown in the docs'
+            pool = tuple(iterable)
+            n = len(pool)
+            if r > n:
+                return
+            indices = range(r)
+            yield tuple(pool[i] for i in indices)
+            while 1:
+                for i in reversed(range(r)):
+                    if indices[i] != i + n - r:
+                        break
+                else:
+                    return
+                indices[i] += 1
+                for j in range(i+1, r):
+                    indices[j] = indices[j-1] + 1
+                yield tuple(pool[i] for i in indices)
+
+        def combinations2(iterable, r):
+            'Pure python version shown in the docs'
+            pool = tuple(iterable)
+            n = len(pool)
+            for indices in permutations(range(n), r):
+                if sorted(indices) == list(indices):
+                    yield tuple(pool[i] for i in indices)
+
+        def combinations3(iterable, r):
+            'Pure python version from cwr()'
+            pool = tuple(iterable)
+            n = len(pool)
+            for indices in combinations_with_replacement(range(n), r):
+                if len(set(indices)) == r:
+                    yield tuple(pool[i] for i in indices)
+
+        for n in range(7):
+            values = [5*x-12 for x in range(n)]
+            for r in range(n+2):
+                result = list(combinations(values, r))
+                self.assertEqual(len(result), 0 if r>n else fact(n) // fact(r) // fact(n-r)) # right number of combs
+                self.assertEqual(len(result), len(set(result)))         # no repeats
+                self.assertEqual(result, sorted(result))                # lexicographic order
+                for c in result:
+                    self.assertEqual(len(c), r)                         # r-length combinations
+                    self.assertEqual(len(set(c)), r)                    # no duplicate elements
+                    self.assertEqual(list(c), sorted(c))                # keep original ordering
+                    self.assertTrue(all(e in values for e in c))           # elements taken from input iterable
+                    self.assertEqual(list(c),
+                                     [e for e in values if e in c])      # comb is a subsequence of the input iterable
+                self.assertEqual(result, list(combinations1(values, r))) # matches first pure python version
+                self.assertEqual(result, list(combinations2(values, r))) # matches second pure python version
+                self.assertEqual(result, list(combinations3(values, r))) # matches second pure python version
+
+        # Test implementation detail:  tuple re-use
+        self.assertEqual(len(set(map(id, combinations('abcde', 3)))), 1)
+        self.assertNotEqual(len(set(map(id, list(combinations('abcde', 3))))), 1)
+
+    def test_combinations_with_replacement(self):
+        cwr = combinations_with_replacement
+        self.assertRaises(TypeError, cwr, 'abc')       # missing r argument
+        self.assertRaises(TypeError, cwr, 'abc', 2, 1) # too many arguments
+        self.assertRaises(TypeError, cwr, None)        # pool is not iterable
+        self.assertRaises(ValueError, cwr, 'abc', -2)  # r is negative
+        self.assertEqual(list(cwr('ABC', 2)),
+                         [('A','A'), ('A','B'), ('A','C'), ('B','B'), ('B','C'), ('C','C')])
+
+        def cwr1(iterable, r):
+            'Pure python version shown in the docs'
+            # number items returned:  (n+r-1)! / r! / (n-1)! when n>0
+            pool = tuple(iterable)
+            n = len(pool)
+            if not n and r:
+                return
+            indices = [0] * r
+            yield tuple(pool[i] for i in indices)
+            while 1:
+                for i in reversed(range(r)):
+                    if indices[i] != n - 1:
+                        break
+                else:
+                    return
+                indices[i:] = [indices[i] + 1] * (r - i)
+                yield tuple(pool[i] for i in indices)
+
+        def cwr2(iterable, r):
+            'Pure python version shown in the docs'
+            pool = tuple(iterable)
+            n = len(pool)
+            for indices in product(range(n), repeat=r):
+                if sorted(indices) == list(indices):
+                    yield tuple(pool[i] for i in indices)
+
+        def numcombs(n, r):
+            if not n:
+                return 0 if r else 1
+            return fact(n+r-1) // fact(r) // fact(n-1)
+
+        for n in range(7):
+            values = [5*x-12 for x in range(n)]
+            for r in range(n+2):
+                result = list(cwr(values, r))
+
+                self.assertEqual(len(result), numcombs(n, r))           # right number of combs
+                self.assertEqual(len(result), len(set(result)))         # no repeats
+                self.assertEqual(result, sorted(result))                # lexicographic order
+
+                regular_combs = list(combinations(values, r))           # compare to combs without replacement
+                if n == 0 or r <= 1:
+                    self.assertEquals(result, regular_combs)            # cases that should be identical
+                else:
+                    self.assertTrue(set(result) >= set(regular_combs))     # rest should be supersets of regular combs
+
+                for c in result:
+                    self.assertEqual(len(c), r)                         # r-length combinations
+                    noruns = [k for k,v in groupby(c)]                  # combo without consecutive repeats
+                    self.assertEqual(len(noruns), len(set(noruns)))     # no repeats other than consecutive
+                    self.assertEqual(list(c), sorted(c))                # keep original ordering
+                    self.assertTrue(all(e in values for e in c))           # elements taken from input iterable
+                    self.assertEqual(noruns,
+                                     [e for e in values if e in c])     # comb is a subsequence of the input iterable
+                self.assertEqual(result, list(cwr1(values, r)))         # matches first pure python version
+                self.assertEqual(result, list(cwr2(values, r)))         # matches second pure python version
+
+        # Test implementation detail:  tuple re-use
+        self.assertEqual(len(set(map(id, cwr('abcde', 3)))), 1)
+        self.assertNotEqual(len(set(map(id, list(cwr('abcde', 3))))), 1)
+
+    def test_permutations(self):
+        self.assertRaises(TypeError, permutations)              # too few arguments
+        self.assertRaises(TypeError, permutations, 'abc', 2, 1) # too many arguments
+        self.assertRaises(TypeError, permutations, None)        # pool is not iterable
+        self.assertRaises(ValueError, permutations, 'abc', -2)  # r is negative
+        self.assertEqual(list(permutations('abc', 32)), [])     # r > n
+        self.assertRaises(TypeError, permutations, 'abc', 's')  # r is not an int or None
+        self.assertEqual(list(permutations(range(3), 2)),
+                                           [(0,1), (0,2), (1,0), (1,2), (2,0), (2,1)])
+
+        def permutations1(iterable, r=None):
+            'Pure python version shown in the docs'
+            pool = tuple(iterable)
+            n = len(pool)
+            r = n if r is None else r
+            if r > n:
+                return
+            indices = range(n)
+            cycles = range(n, n-r, -1)
+            yield tuple(pool[i] for i in indices[:r])
+            while n:
+                for i in reversed(range(r)):
+                    cycles[i] -= 1
+                    if cycles[i] == 0:
+                        indices[i:] = indices[i+1:] + indices[i:i+1]
+                        cycles[i] = n - i
+                    else:
+                        j = cycles[i]
+                        indices[i], indices[-j] = indices[-j], indices[i]
+                        yield tuple(pool[i] for i in indices[:r])
+                        break
+                else:
+                    return
+
+        def permutations2(iterable, r=None):
+            'Pure python version shown in the docs'
+            pool = tuple(iterable)
+            n = len(pool)
+            r = n if r is None else r
+            for indices in product(range(n), repeat=r):
+                if len(set(indices)) == r:
+                    yield tuple(pool[i] for i in indices)
+
+        for n in range(7):
+            values = [5*x-12 for x in range(n)]
+            for r in range(n+2):
+                result = list(permutations(values, r))
+                self.assertEqual(len(result), 0 if r>n else fact(n) // fact(n-r))      # right number of perms
+                self.assertEqual(len(result), len(set(result)))         # no repeats
+                self.assertEqual(result, sorted(result))                # lexicographic order
+                for p in result:
+                    self.assertEqual(len(p), r)                         # r-length permutations
+                    self.assertEqual(len(set(p)), r)                    # no duplicate elements
+                    self.assertTrue(all(e in values for e in p))           # elements taken from input iterable
+                self.assertEqual(result, list(permutations1(values, r))) # matches first pure python version
+                self.assertEqual(result, list(permutations2(values, r))) # matches second pure python version
+                if r == n:
+                    self.assertEqual(result, list(permutations(values, None))) # test r as None
+                    self.assertEqual(result, list(permutations(values)))       # test default r
+
+        # Test implementation detail:  tuple re-use
+        self.assertEqual(len(set(map(id, permutations('abcde', 3)))), 1)
+        self.assertNotEqual(len(set(map(id, list(permutations('abcde', 3))))), 1)
+
+    def test_combinatorics(self):
+        # Test relationships between product(), permutations(),
+        # combinations() and combinations_with_replacement().
+
+        for n in range(6):
+            s = 'ABCDEFG'[:n]
+            for r in range(8):
+                prod = list(product(s, repeat=r))
+                cwr = list(combinations_with_replacement(s, r))
+                perm = list(permutations(s, r))
+                comb = list(combinations(s, r))
+
+                # Check size
+                self.assertEquals(len(prod), n**r)
+                self.assertEquals(len(cwr), (fact(n+r-1) // fact(r) // fact(n-1)) if n else (not r))
+                self.assertEquals(len(perm), 0 if r>n else fact(n) // fact(n-r))
+                self.assertEquals(len(comb), 0 if r>n else fact(n) // fact(r) // fact(n-r))
+
+                # Check lexicographic order without repeated tuples
+                self.assertEquals(prod, sorted(set(prod)))
+                self.assertEquals(cwr, sorted(set(cwr)))
+                self.assertEquals(perm, sorted(set(perm)))
+                self.assertEquals(comb, sorted(set(comb)))
+
+                # Check interrelationships
+                self.assertEquals(cwr, [t for t in prod if sorted(t)==list(t)]) # cwr: prods which are sorted
+                self.assertEquals(perm, [t for t in prod if len(set(t))==r])    # perm: prods with no dups
+                self.assertEqual(comb, [t for t in perm if sorted(t)==list(t)]) # comb: perms that are sorted
+                self.assertEqual(comb, [t for t in cwr if len(set(t))==r])      # comb: cwrs without dups
+                self.assertEqual(comb, filter(set(cwr).__contains__, perm))     # comb: perm that is a cwr
+                self.assertEqual(comb, filter(set(perm).__contains__, cwr))     # comb: cwr that is a perm
+                self.assertEqual(comb, sorted(set(cwr) & set(perm)))            # comb: both a cwr and a perm
+
+    def test_compress(self):
+        self.assertEqual(list(compress(data='ABCDEF', selectors=[1,0,1,0,1,1])), list('ACEF'))
+        self.assertEqual(list(compress('ABCDEF', [1,0,1,0,1,1])), list('ACEF'))
+        self.assertEqual(list(compress('ABCDEF', [0,0,0,0,0,0])), list(''))
+        self.assertEqual(list(compress('ABCDEF', [1,1,1,1,1,1])), list('ABCDEF'))
+        self.assertEqual(list(compress('ABCDEF', [1,0,1])), list('AC'))
+        self.assertEqual(list(compress('ABC', [0,1,1,1,1,1])), list('BC'))
+        n = 10000
+        data = chain.from_iterable(repeat(range(6), n))
+        selectors = chain.from_iterable(repeat((0, 1)))
+        self.assertEqual(list(compress(data, selectors)), [1,3,5] * n)
+        self.assertRaises(TypeError, compress, None, range(6))      # 1st arg not iterable
+        self.assertRaises(TypeError, compress, range(6), None)      # 2nd arg not iterable
+        self.assertRaises(TypeError, compress, range(6))            # too few args
+        self.assertRaises(TypeError, compress, range(6), None)      # too many args
+
+    def test_count(self):
+        self.assertEqual(zip('abc',count()), [('a', 0), ('b', 1), ('c', 2)])
+        self.assertEqual(zip('abc',count(3)), [('a', 3), ('b', 4), ('c', 5)])
+        self.assertEqual(take(2, zip('abc',count(3))), [('a', 3), ('b', 4)])
+        self.assertEqual(take(2, zip('abc',count(-1))), [('a', -1), ('b', 0)])
+        self.assertEqual(take(2, zip('abc',count(-3))), [('a', -3), ('b', -2)])
+        self.assertRaises(TypeError, count, 2, 3, 4)
+        self.assertRaises(TypeError, count, 'a')
+        self.assertEqual(list(islice(count(maxsize-5), 10)), range(maxsize-5, maxsize+5))
+        self.assertEqual(list(islice(count(-maxsize-5), 10)), range(-maxsize-5, -maxsize+5))
+        c = count(3)
+        self.assertEqual(repr(c), 'count(3)')
+        c.next()
+        self.assertEqual(repr(c), 'count(4)')
+        c = count(-9)
+        self.assertEqual(repr(c), 'count(-9)')
+        c.next()
+        self.assertEqual(repr(count(10.25)), 'count(10.25)')
+        self.assertEqual(c.next(), -8)
+        for i in (-sys.maxint-5, -sys.maxint+5 ,-10, -1, 0, 10, sys.maxint-5, sys.maxint+5):
+            # Test repr (ignoring the L in longs)
+            r1 = repr(count(i)).replace('L', '')
+            r2 = 'count(%r)'.__mod__(i).replace('L', '')
+            self.assertEqual(r1, r2)
+
+        # check copy, deepcopy, pickle
+        for value in -3, 3, sys.maxint-5, sys.maxint+5:
+            c = count(value)
+            self.assertEqual(next(copy.copy(c)), value)
+            self.assertEqual(next(copy.deepcopy(c)), value)
+            self.assertEqual(next(pickle.loads(pickle.dumps(c))), value)
+
+    def test_count_with_stride(self):
+        self.assertEqual(zip('abc',count(2,3)), [('a', 2), ('b', 5), ('c', 8)])
+        self.assertEqual(zip('abc',count(start=2,step=3)),
+                         [('a', 2), ('b', 5), ('c', 8)])
+        self.assertEqual(zip('abc',count(step=-1)),
+                         [('a', 0), ('b', -1), ('c', -2)])
+        self.assertEqual(zip('abc',count(2,0)), [('a', 2), ('b', 2), ('c', 2)])
+        self.assertEqual(zip('abc',count(2,1)), [('a', 2), ('b', 3), ('c', 4)])
+        self.assertEqual(take(20, count(maxsize-15, 3)), take(20, range(maxsize-15, maxsize+100, 3)))
+        self.assertEqual(take(20, count(-maxsize-15, 3)), take(20, range(-maxsize-15,-maxsize+100, 3)))
+        self.assertEqual(take(3, count(2, 3.25-4j)), [2, 5.25-4j, 8.5-8j])
+        self.assertEqual(take(3, count(Decimal('1.1'), Decimal('.1'))),
+                         [Decimal('1.1'), Decimal('1.2'), Decimal('1.3')])
+        self.assertEqual(take(3, count(Fraction(2,3), Fraction(1,7))),
+                         [Fraction(2,3), Fraction(17,21), Fraction(20,21)])
+        self.assertEqual(repr(take(3, count(10, 2.5))), repr([10, 12.5, 15.0]))
+        c = count(3, 5)
+        self.assertEqual(repr(c), 'count(3, 5)')
+        c.next()
+        self.assertEqual(repr(c), 'count(8, 5)')
+        c = count(-9, 0)
+        self.assertEqual(repr(c), 'count(-9, 0)')
+        c.next()
+        self.assertEqual(repr(c), 'count(-9, 0)')
+        c = count(-9, -3)
+        self.assertEqual(repr(c), 'count(-9, -3)')
+        c.next()
+        self.assertEqual(repr(c), 'count(-12, -3)')
+        self.assertEqual(repr(c), 'count(-12, -3)')
+        self.assertEqual(repr(count(10.5, 1.25)), 'count(10.5, 1.25)')
+        self.assertEqual(repr(count(10.5, 1)), 'count(10.5)')           # suppress step=1 when it's an int
+        self.assertEqual(repr(count(10.5, 1.00)), 'count(10.5, 1.0)')   # do show float values lilke 1.0
+        for i in (-sys.maxint-5, -sys.maxint+5 ,-10, -1, 0, 10, sys.maxint-5, sys.maxint+5):
+            for j in  (-sys.maxint-5, -sys.maxint+5 ,-10, -1, 0, 1, 10, sys.maxint-5, sys.maxint+5):
+                # Test repr (ignoring the L in longs)
+                r1 = repr(count(i, j)).replace('L', '')
+                if j == 1:
+                    r2 = ('count(%r)' % i).replace('L', '')
+                else:
+                    r2 = ('count(%r, %r)' % (i, j)).replace('L', '')
+                self.assertEqual(r1, r2)
+
+    def test_cycle(self):
+        self.assertEqual(take(10, cycle('abc')), list('abcabcabca'))
+        self.assertEqual(list(cycle('')), [])
+        self.assertRaises(TypeError, cycle)
+        self.assertRaises(TypeError, cycle, 5)
+        self.assertEqual(list(islice(cycle(gen3()),10)), [0,1,2,0,1,2,0,1,2,0])
+
+    def test_groupby(self):
+        # Check whether it accepts arguments correctly
+        self.assertEqual([], list(groupby([])))
+        self.assertEqual([], list(groupby([], key=id)))
+        self.assertRaises(TypeError, list, groupby('abc', []))
+        self.assertRaises(TypeError, groupby, None)
+        self.assertRaises(TypeError, groupby, 'abc', lambda x:x, 10)
+
+        # Check normal input
+        s = [(0, 10, 20), (0, 11,21), (0,12,21), (1,13,21), (1,14,22),
+             (2,15,22), (3,16,23), (3,17,23)]
+        dup = []
+        for k, g in groupby(s, lambda r:r[0]):
+            for elem in g:
+                self.assertEqual(k, elem[0])
+                dup.append(elem)
+        self.assertEqual(s, dup)
+
+        # Check nested case
+        dup = []
+        for k, g in groupby(s, lambda r:r[0]):
+            for ik, ig in groupby(g, lambda r:r[2]):
+                for elem in ig:
+                    self.assertEqual(k, elem[0])
+                    self.assertEqual(ik, elem[2])
+                    dup.append(elem)
+        self.assertEqual(s, dup)
+
+        # Check case where inner iterator is not used
+        keys = [k for k, g in groupby(s, lambda r:r[0])]
+        expectedkeys = set([r[0] for r in s])
+        self.assertEqual(set(keys), expectedkeys)
+        self.assertEqual(len(keys), len(expectedkeys))
+
+        # Exercise pipes and filters style
+        s = 'abracadabra'
+        # sort s | uniq
+        r = [k for k, g in groupby(sorted(s))]
+        self.assertEqual(r, ['a', 'b', 'c', 'd', 'r'])
+        # sort s | uniq -d
+        r = [k for k, g in groupby(sorted(s)) if list(islice(g,1,2))]
+        self.assertEqual(r, ['a', 'b', 'r'])
+        # sort s | uniq -c
+        r = [(len(list(g)), k) for k, g in groupby(sorted(s))]
+        self.assertEqual(r, [(5, 'a'), (2, 'b'), (1, 'c'), (1, 'd'), (2, 'r')])
+        # sort s | uniq -c | sort -rn | head -3
+        r = sorted([(len(list(g)) , k) for k, g in groupby(sorted(s))], reverse=True)[:3]
+        self.assertEqual(r, [(5, 'a'), (2, 'r'), (2, 'b')])
+
+        # iter.next failure
+        class ExpectedError(Exception):
+            pass
+        def delayed_raise(n=0):
+            for i in range(n):
+                yield 'yo'
+            raise ExpectedError
+        def gulp(iterable, keyp=None, func=list):
+            return [func(g) for k, g in groupby(iterable, keyp)]
+
+        # iter.next failure on outer object
+        self.assertRaises(ExpectedError, gulp, delayed_raise(0))
+        # iter.next failure on inner object
+        self.assertRaises(ExpectedError, gulp, delayed_raise(1))
+
+        # __cmp__ failure
+        class DummyCmp:
+            def __cmp__(self, dst):
+                raise ExpectedError
+        s = [DummyCmp(), DummyCmp(), None]
+
+        # __cmp__ failure on outer object
+        self.assertRaises(ExpectedError, gulp, s, func=id)
+        # __cmp__ failure on inner object
+        self.assertRaises(ExpectedError, gulp, s)
+
+        # keyfunc failure
+        def keyfunc(obj):
+            if keyfunc.skip > 0:
+                keyfunc.skip -= 1
+                return obj
+            else:
+                raise ExpectedError
+
+        # keyfunc failure on outer object
+        keyfunc.skip = 0
+        self.assertRaises(ExpectedError, gulp, [None], keyfunc)
+        keyfunc.skip = 1
+        self.assertRaises(ExpectedError, gulp, [None, None], keyfunc)
+
+    def test_ifilter(self):
+        self.assertEqual(list(ifilter(isEven, range(6))), [0,2,4])
+        self.assertEqual(list(ifilter(None, [0,1,0,2,0])), [1,2])
+        self.assertEqual(list(ifilter(bool, [0,1,0,2,0])), [1,2])
+        self.assertEqual(take(4, ifilter(isEven, count())), [0,2,4,6])
+        self.assertRaises(TypeError, ifilter)
+        self.assertRaises(TypeError, ifilter, lambda x:x)
+        self.assertRaises(TypeError, ifilter, lambda x:x, range(6), 7)
+        self.assertRaises(TypeError, ifilter, isEven, 3)
+        self.assertRaises(TypeError, ifilter(range(6), range(6)).next)
+
+    def test_ifilterfalse(self):
+        self.assertEqual(list(ifilterfalse(isEven, range(6))), [1,3,5])
+        self.assertEqual(list(ifilterfalse(None, [0,1,0,2,0])), [0,0,0])
+        self.assertEqual(list(ifilterfalse(bool, [0,1,0,2,0])), [0,0,0])
+        self.assertEqual(take(4, ifilterfalse(isEven, count())), [1,3,5,7])
+        self.assertRaises(TypeError, ifilterfalse)
+        self.assertRaises(TypeError, ifilterfalse, lambda x:x)
+        self.assertRaises(TypeError, ifilterfalse, lambda x:x, range(6), 7)
+        self.assertRaises(TypeError, ifilterfalse, isEven, 3)
+        self.assertRaises(TypeError, ifilterfalse(range(6), range(6)).next)
+
+    def test_izip(self):
+        ans = [(x,y) for x, y in izip('abc',count())]
+        self.assertEqual(ans, [('a', 0), ('b', 1), ('c', 2)])
+        self.assertEqual(list(izip('abc', range(6))), zip('abc', range(6)))
+        self.assertEqual(list(izip('abcdef', range(3))), zip('abcdef', range(3)))
+        self.assertEqual(take(3,izip('abcdef', count())), zip('abcdef', range(3)))
+        self.assertEqual(list(izip('abcdef')), zip('abcdef'))
+        self.assertEqual(list(izip()), zip())
+        self.assertRaises(TypeError, izip, 3)
+        self.assertRaises(TypeError, izip, range(3), 3)
+        # Check tuple re-use (implementation detail)
+        self.assertEqual([tuple(list(pair)) for pair in izip('abc', 'def')],
+                         zip('abc', 'def'))
+        self.assertEqual([pair for pair in izip('abc', 'def')],
+                         zip('abc', 'def'))
+        ids = map(id, izip('abc', 'def'))
+        self.assertEqual(min(ids), max(ids))
+        ids = map(id, list(izip('abc', 'def')))
+        self.assertEqual(len(dict.fromkeys(ids)), len(ids))
+
+    def test_iziplongest(self):
+        for args in [
+                ['abc', range(6)],
+                [range(6), 'abc'],
+                [range(1000), range(2000,2100), range(3000,3050)],
+                [range(1000), range(0), range(3000,3050), range(1200), range(1500)],
+                [range(1000), range(0), range(3000,3050), range(1200), range(1500), range(0)],
+            ]:
+            # target = map(None, *args) <- this raises a py3k warning
+            # this is the replacement:
+            target = [tuple([arg[i] if i < len(arg) else None for arg in args])
+                      for i in range(max(map(len, args)))]
+            self.assertEqual(list(izip_longest(*args)), target)
+            self.assertEqual(list(izip_longest(*args, **{})), target)
+            target = [tuple((e is None and 'X' or e) for e in t) for t in target]   # Replace None fills with 'X'
+            self.assertEqual(list(izip_longest(*args, **dict(fillvalue='X'))), target)
+
+        self.assertEqual(take(3,izip_longest('abcdef', count())), zip('abcdef', range(3))) # take 3 from infinite input
+
+        self.assertEqual(list(izip_longest()), zip())
+        self.assertEqual(list(izip_longest([])), zip([]))
+        self.assertEqual(list(izip_longest('abcdef')), zip('abcdef'))
+
+        self.assertEqual(list(izip_longest('abc', 'defg', **{})),
+                         zip(list('abc') + [None], 'defg'))  # empty keyword dict
+        self.assertRaises(TypeError, izip_longest, 3)
+        self.assertRaises(TypeError, izip_longest, range(3), 3)
+
+        for stmt in [
+            "izip_longest('abc', fv=1)",
+            "izip_longest('abc', fillvalue=1, bogus_keyword=None)",
+        ]:
+            try:
+                eval(stmt, globals(), locals())
+            except TypeError:
+                pass
+            else:
+                self.fail('Did not raise Type in:  ' + stmt)
+
+        # Check tuple re-use (implementation detail)
+        self.assertEqual([tuple(list(pair)) for pair in izip_longest('abc', 'def')],
+                         zip('abc', 'def'))
+        self.assertEqual([pair for pair in izip_longest('abc', 'def')],
+                         zip('abc', 'def'))
+        ids = map(id, izip_longest('abc', 'def'))
+        self.assertEqual(min(ids), max(ids))
+        ids = map(id, list(izip_longest('abc', 'def')))
+        self.assertEqual(len(dict.fromkeys(ids)), len(ids))
+
+    def test_bug_7244(self):
+
+        class Repeater(object):
+            # this class is similar to itertools.repeat
+            def __init__(self, o, t, e):
+                self.o = o
+                self.t = int(t)
+                self.e = e
+            def __iter__(self): # its iterator is itself
+                return self
+            def next(self):
+                if self.t > 0:
+                    self.t -= 1
+                    return self.o
+                else:
+                    raise self.e
+
+        # Formerly this code in would fail in debug mode
+        # with Undetected Error and Stop Iteration
+        r1 = Repeater(1, 3, StopIteration)
+        r2 = Repeater(2, 4, StopIteration)
+        def run(r1, r2):
+            result = []
+            for i, j in izip_longest(r1, r2, fillvalue=0):
+                with test_support.captured_output('stdout'):
+                    print (i, j)
+                result.append((i, j))
+            return result
+        self.assertEqual(run(r1, r2), [(1,2), (1,2), (1,2), (0,2)])
+
+        # Formerly, the RuntimeError would be lost
+        # and StopIteration would stop as expected
+        r1 = Repeater(1, 3, RuntimeError)
+        r2 = Repeater(2, 4, StopIteration)
+        it = izip_longest(r1, r2, fillvalue=0)
+        self.assertEqual(next(it), (1, 2))
+        self.assertEqual(next(it), (1, 2))
+        self.assertEqual(next(it), (1, 2))
+        self.assertRaises(RuntimeError, next, it)
+
+    def test_product(self):
+        for args, result in [
+            ([], [()]),                     # zero iterables
+            (['ab'], [('a',), ('b',)]),     # one iterable
+            ([range(2), range(3)], [(0,0), (0,1), (0,2), (1,0), (1,1), (1,2)]),     # two iterables
+            ([range(0), range(2), range(3)], []),           # first iterable with zero length
+            ([range(2), range(0), range(3)], []),           # middle iterable with zero length
+            ([range(2), range(3), range(0)], []),           # last iterable with zero length
+            ]:
+            self.assertEqual(list(product(*args)), result)
+            for r in range(4):
+                self.assertEqual(list(product(*(args*r))),
+                                 list(product(*args, **dict(repeat=r))))
+        self.assertEqual(len(list(product(*[range(7)]*6))), 7**6)
+        self.assertRaises(TypeError, product, range(6), None)
+
+        def product1(*args, **kwds):
+            pools = map(tuple, args) * kwds.get('repeat', 1)
+            n = len(pools)
+            if n == 0:
+                yield ()
+                return
+            if any(len(pool) == 0 for pool in pools):
+                return
+            indices = [0] * n
+            yield tuple(pool[i] for pool, i in zip(pools, indices))
+            while 1:
+                for i in reversed(range(n)):  # right to left
+                    if indices[i] == len(pools[i]) - 1:
+                        continue
+                    indices[i] += 1
+                    for j in range(i+1, n):
+                        indices[j] = 0
+                    yield tuple(pool[i] for pool, i in zip(pools, indices))
+                    break
+                else:
+                    return
+
+        def product2(*args, **kwds):
+            'Pure python version used in docs'
+            pools = map(tuple, args) * kwds.get('repeat', 1)
+            result = [[]]
+            for pool in pools:
+                result = [x+[y] for x in result for y in pool]
+            for prod in result:
+                yield tuple(prod)
+
+        argtypes = ['', 'abc', '', xrange(0), xrange(4), dict(a=1, b=2, c=3),
+                    set('abcdefg'), range(11), tuple(range(13))]
+        for i in range(100):
+            args = [random.choice(argtypes) for j in range(random.randrange(5))]
+            expected_len = prod(map(len, args))
+            self.assertEqual(len(list(product(*args))), expected_len)
+            self.assertEqual(list(product(*args)), list(product1(*args)))
+            self.assertEqual(list(product(*args)), list(product2(*args)))
+            args = map(iter, args)
+            self.assertEqual(len(list(product(*args))), expected_len)
+
+        # Test implementation detail:  tuple re-use
+        self.assertEqual(len(set(map(id, product('abc', 'def')))), 1)
+        self.assertNotEqual(len(set(map(id, list(product('abc', 'def'))))), 1)
+
+    def test_repeat(self):
+        self.assertEqual(list(repeat(object='a', times=3)), ['a', 'a', 'a'])
+        self.assertEqual(zip(xrange(3),repeat('a')),
+                         [(0, 'a'), (1, 'a'), (2, 'a')])
+        self.assertEqual(list(repeat('a', 3)), ['a', 'a', 'a'])
+        self.assertEqual(take(3, repeat('a')), ['a', 'a', 'a'])
+        self.assertEqual(list(repeat('a', 0)), [])
+        self.assertEqual(list(repeat('a', -3)), [])
+        self.assertRaises(TypeError, repeat)
+        self.assertRaises(TypeError, repeat, None, 3, 4)
+        self.assertRaises(TypeError, repeat, None, 'a')
+        r = repeat(1+0j)
+        self.assertEqual(repr(r), 'repeat((1+0j))')
+        r = repeat(1+0j, 5)
+        self.assertEqual(repr(r), 'repeat((1+0j), 5)')
+        list(r)
+        self.assertEqual(repr(r), 'repeat((1+0j), 0)')
+
+    def test_imap(self):
+        self.assertEqual(list(imap(operator.pow, range(3), range(1,7))),
+                         [0**1, 1**2, 2**3])
+        self.assertEqual(list(imap(None, 'abc', range(5))),
+                         [('a',0),('b',1),('c',2)])
+        self.assertEqual(list(imap(None, 'abc', count())),
+                         [('a',0),('b',1),('c',2)])
+        self.assertEqual(take(2,imap(None, 'abc', count())),
+                         [('a',0),('b',1)])
+        self.assertEqual(list(imap(operator.pow, [])), [])
+        self.assertRaises(TypeError, imap)
+        self.assertRaises(TypeError, imap, operator.neg)
+        self.assertRaises(TypeError, imap(10, range(5)).next)
+        self.assertRaises(ValueError, imap(errfunc, [4], [5]).next)
+        self.assertRaises(TypeError, imap(onearg, [4], [5]).next)
+
+    def test_starmap(self):
+        self.assertEqual(list(starmap(operator.pow, zip(range(3), range(1,7)))),
+                         [0**1, 1**2, 2**3])
+        self.assertEqual(take(3, starmap(operator.pow, izip(count(), count(1)))),
+                         [0**1, 1**2, 2**3])
+        self.assertEqual(list(starmap(operator.pow, [])), [])
+        self.assertEqual(list(starmap(operator.pow, [iter([4,5])])), [4**5])
+        self.assertRaises(TypeError, list, starmap(operator.pow, [None]))
+        self.assertRaises(TypeError, starmap)
+        self.assertRaises(TypeError, starmap, operator.pow, [(4,5)], 'extra')
+        self.assertRaises(TypeError, starmap(10, [(4,5)]).next)
+        self.assertRaises(ValueError, starmap(errfunc, [(4,5)]).next)
+        self.assertRaises(TypeError, starmap(onearg, [(4,5)]).next)
+
+    def test_islice(self):
+        for args in [          # islice(args) should agree with range(args)
+                (10, 20, 3),
+                (10, 3, 20),
+                (10, 20),
+                (10, 3),
+                (20,)
+                ]:
+            self.assertEqual(list(islice(xrange(100), *args)), range(*args))
+
+        for args, tgtargs in [  # Stop when seqn is exhausted
+                ((10, 110, 3), ((10, 100, 3))),
+                ((10, 110), ((10, 100))),
+                ((110,), (100,))
+                ]:
+            self.assertEqual(list(islice(xrange(100), *args)), range(*tgtargs))
+
+        # Test stop=None
+        self.assertEqual(list(islice(xrange(10), None)), range(10))
+        self.assertEqual(list(islice(xrange(10), None, None)), range(10))
+        self.assertEqual(list(islice(xrange(10), None, None, None)), range(10))
+        self.assertEqual(list(islice(xrange(10), 2, None)), range(2, 10))
+        self.assertEqual(list(islice(xrange(10), 1, None, 2)), range(1, 10, 2))
+
+        # Test number of items consumed     SF #1171417
+        it = iter(range(10))
+        self.assertEqual(list(islice(it, 3)), range(3))
+        self.assertEqual(list(it), range(3, 10))
+
+        # Test invalid arguments
+        self.assertRaises(TypeError, islice, xrange(10))
+        self.assertRaises(TypeError, islice, xrange(10), 1, 2, 3, 4)
+        self.assertRaises(ValueError, islice, xrange(10), -5, 10, 1)
+        self.assertRaises(ValueError, islice, xrange(10), 1, -5, -1)
+        self.assertRaises(ValueError, islice, xrange(10), 1, 10, -1)
+        self.assertRaises(ValueError, islice, xrange(10), 1, 10, 0)
+        self.assertRaises(ValueError, islice, xrange(10), 'a')
+        self.assertRaises(ValueError, islice, xrange(10), 'a', 1)
+        self.assertRaises(ValueError, islice, xrange(10), 1, 'a')
+        self.assertRaises(ValueError, islice, xrange(10), 'a', 1, 1)
+        self.assertRaises(ValueError, islice, xrange(10), 1, 'a', 1)
+        self.assertEqual(len(list(islice(count(), 1, 10, maxsize))), 1)
+
+    def test_takewhile(self):
+        data = [1, 3, 5, 20, 2, 4, 6, 8]
+        underten = lambda x: x<10
+        self.assertEqual(list(takewhile(underten, data)), [1, 3, 5])
+        self.assertEqual(list(takewhile(underten, [])), [])
+        self.assertRaises(TypeError, takewhile)
+        self.assertRaises(TypeError, takewhile, operator.pow)
+        self.assertRaises(TypeError, takewhile, operator.pow, [(4,5)], 'extra')
+        self.assertRaises(TypeError, takewhile(10, [(4,5)]).next)
+        self.assertRaises(ValueError, takewhile(errfunc, [(4,5)]).next)
+        t = takewhile(bool, [1, 1, 1, 0, 0, 0])
+        self.assertEqual(list(t), [1, 1, 1])
+        self.assertRaises(StopIteration, t.next)
+
+    def test_dropwhile(self):
+        data = [1, 3, 5, 20, 2, 4, 6, 8]
+        underten = lambda x: x<10
+        self.assertEqual(list(dropwhile(underten, data)), [20, 2, 4, 6, 8])
+        self.assertEqual(list(dropwhile(underten, [])), [])
+        self.assertRaises(TypeError, dropwhile)
+        self.assertRaises(TypeError, dropwhile, operator.pow)
+        self.assertRaises(TypeError, dropwhile, operator.pow, [(4,5)], 'extra')
+        self.assertRaises(TypeError, dropwhile(10, [(4,5)]).next)
+        self.assertRaises(ValueError, dropwhile(errfunc, [(4,5)]).next)
+
+    def test_tee(self):
+        n = 200
+        def irange(n):
+            for i in xrange(n):
+                yield i
+
+        a, b = tee([])        # test empty iterator
+        self.assertEqual(list(a), [])
+        self.assertEqual(list(b), [])
+
+        a, b = tee(irange(n)) # test 100% interleaved
+        self.assertEqual(zip(a,b), zip(range(n),range(n)))
+
+        a, b = tee(irange(n)) # test 0% interleaved
+        self.assertEqual(list(a), range(n))
+        self.assertEqual(list(b), range(n))
+
+        a, b = tee(irange(n)) # test dealloc of leading iterator
+        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
+        for i in xrange(100):
+            self.assertEqual(a.next(), i)
+        del b
+        self.assertEqual(list(a), range(100, n))
+
+        for j in xrange(5):   # test randomly interleaved
+            order = [0]*n + [1]*n
+            random.shuffle(order)
+            lists = ([], [])
+            its = tee(irange(n))
+            for i in order:
+                value = its[i].next()
+                lists[i].append(value)
+            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')
+
+        # 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))
+
+        # test values of n
+        self.assertRaises(TypeError, tee, 'abc', 'invalid')
+        self.assertRaises(ValueError, tee, [], -1)
+        for n in xrange(5):
+            result = tee('abc', n)
+            self.assertEqual(type(result), tuple)
+            self.assertEqual(len(result), n)
+            self.assertEqual(map(list, result), [list('abc')]*n)
+
+        # tee pass-through to copyable iterator
+        a, b = tee('abc')
+        c, d = tee(a)
+        self.assertTrue(a is c)
+
+        # test tee_new
+        t1, t2 = tee('abc')
+        tnew = type(t1)
+        self.assertRaises(TypeError, tnew)
+        self.assertRaises(TypeError, tnew, 10)
+        t3 = tnew(t1)
+        self.assertTrue(list(t1) == list(t2) == list(t3) == list('abc'))
+
+        # test that tee objects are weak referencable
+        a, b = tee(xrange(10))
+        p = proxy(a)
+        self.assertEqual(getattr(p, '__class__'), type(b))
+        del a
+        self.assertRaises(ReferenceError, getattr, p, '__class__')
+
+    def test_StopIteration(self):
+        self.assertRaises(StopIteration, izip().next)
+
+        for f in (chain, cycle, izip, groupby):
+            self.assertRaises(StopIteration, f([]).next)
+            self.assertRaises(StopIteration, f(StopNow()).next)
+
+        self.assertRaises(StopIteration, islice([], None).next)
+        self.assertRaises(StopIteration, islice(StopNow(), None).next)
+
+        p, q = tee([])
+        self.assertRaises(StopIteration, p.next)
+        self.assertRaises(StopIteration, q.next)
+        p, q = tee(StopNow())
+        self.assertRaises(StopIteration, p.next)
+        self.assertRaises(StopIteration, q.next)
+
+        self.assertRaises(StopIteration, repeat(None, 0).next)
+
+        for f in (ifilter, ifilterfalse, imap, takewhile, dropwhile, starmap):
+            self.assertRaises(StopIteration, f(lambda x:x, []).next)
+            self.assertRaises(StopIteration, f(lambda x:x, StopNow()).next)
+
+class TestExamples(unittest.TestCase):
+
+    def test_chain(self):
+        self.assertEqual(''.join(chain('ABC', 'DEF')), 'ABCDEF')
+
+    def test_chain_from_iterable(self):
+        self.assertEqual(''.join(chain.from_iterable(['ABC', 'DEF'])), 'ABCDEF')
+
+    def test_combinations(self):
+        self.assertEqual(list(combinations('ABCD', 2)),
+                         [('A','B'), ('A','C'), ('A','D'), ('B','C'), ('B','D'), ('C','D')])
+        self.assertEqual(list(combinations(range(4), 3)),
+                         [(0,1,2), (0,1,3), (0,2,3), (1,2,3)])
+
+    def test_combinations_with_replacement(self):
+        self.assertEqual(list(combinations_with_replacement('ABC', 2)),
+                         [('A','A'), ('A','B'), ('A','C'), ('B','B'), ('B','C'), ('C','C')])
+
+    def test_compress(self):
+        self.assertEqual(list(compress('ABCDEF', [1,0,1,0,1,1])), list('ACEF'))
+
+    def test_count(self):
+        self.assertEqual(list(islice(count(10), 5)), [10, 11, 12, 13, 14])
+
+    def test_cycle(self):
+        self.assertEqual(list(islice(cycle('ABCD'), 12)), list('ABCDABCDABCD'))
+
+    def test_dropwhile(self):
+        self.assertEqual(list(dropwhile(lambda x: x<5, [1,4,6,4,1])), [6,4,1])
+
+    def test_groupby(self):
+        self.assertEqual([k for k, g in groupby('AAAABBBCCDAABBB')],
+                         list('ABCDAB'))
+        self.assertEqual([(list(g)) for k, g in groupby('AAAABBBCCD')],
+                         [list('AAAA'), list('BBB'), list('CC'), list('D')])
+
+    def test_ifilter(self):
+        self.assertEqual(list(ifilter(lambda x: x%2, range(10))), [1,3,5,7,9])
+
+    def test_ifilterfalse(self):
+        self.assertEqual(list(ifilterfalse(lambda x: x%2, range(10))), [0,2,4,6,8])
+
+    def test_imap(self):
+        self.assertEqual(list(imap(pow, (2,3,10), (5,2,3))), [32, 9, 1000])
+
+    def test_islice(self):
+        self.assertEqual(list(islice('ABCDEFG', 2)), list('AB'))
+        self.assertEqual(list(islice('ABCDEFG', 2, 4)), list('CD'))
+        self.assertEqual(list(islice('ABCDEFG', 2, None)), list('CDEFG'))
+        self.assertEqual(list(islice('ABCDEFG', 0, None, 2)), list('ACEG'))
+
+    def test_izip(self):
+        self.assertEqual(list(izip('ABCD', 'xy')), [('A', 'x'), ('B', 'y')])
+
+    def test_izip_longest(self):
+        self.assertEqual(list(izip_longest('ABCD', 'xy', fillvalue='-')),
+                         [('A', 'x'), ('B', 'y'), ('C', '-'), ('D', '-')])
+
+    def test_permutations(self):
+        self.assertEqual(list(permutations('ABCD', 2)),
+                         map(tuple, 'AB AC AD BA BC BD CA CB CD DA DB DC'.split()))
+        self.assertEqual(list(permutations(range(3))),
+                         [(0,1,2), (0,2,1), (1,0,2), (1,2,0), (2,0,1), (2,1,0)])
+
+    def test_product(self):
+        self.assertEqual(list(product('ABCD', 'xy')),
+                         map(tuple, 'Ax Ay Bx By Cx Cy Dx Dy'.split()))
+        self.assertEqual(list(product(range(2), repeat=3)),
+                        [(0,0,0), (0,0,1), (0,1,0), (0,1,1),
+                         (1,0,0), (1,0,1), (1,1,0), (1,1,1)])
+
+    def test_repeat(self):
+        self.assertEqual(list(repeat(10, 3)), [10, 10, 10])
+
+    def test_stapmap(self):
+        self.assertEqual(list(starmap(pow, [(2,5), (3,2), (10,3)])),
+                         [32, 9, 1000])
+
+    def test_takewhile(self):
+        self.assertEqual(list(takewhile(lambda x: x<5, [1,4,6,4,1])), [1,4])
+
+
+class TestGC(unittest.TestCase):
+
+    def makecycle(self, iterator, container):
+        container.append(iterator)
+        iterator.next()
+        del container, iterator
+
+    def test_chain(self):
+        a = []
+        self.makecycle(chain(a), a)
+
+    def test_chain_from_iterable(self):
+        a = []
+        self.makecycle(chain.from_iterable([a]), a)
+
+    def test_combinations(self):
+        a = []
+        self.makecycle(combinations([1,2,a,3], 3), a)
+
+    def test_combinations_with_replacement(self):
+        a = []
+        self.makecycle(combinations_with_replacement([1,2,a,3], 3), a)
+
+    def test_compress(self):
+        a = []
+        self.makecycle(compress('ABCDEF', [1,0,1,0,1,0]), a)
+
+    def test_count(self):
+        a = []
+        Int = type('Int', (int,), dict(x=a))
+        self.makecycle(count(Int(0), Int(1)), a)
+
+    def test_cycle(self):
+        a = []
+        self.makecycle(cycle([a]*2), a)
+
+    def test_dropwhile(self):
+        a = []
+        self.makecycle(dropwhile(bool, [0, a, a]), a)
+
+    def test_groupby(self):
+        a = []
+        self.makecycle(groupby([a]*2, lambda x:x), a)
+
+    def test_issue2246(self):
+        # Issue 2246 -- the _grouper iterator was not included in GC
+        n = 10
+        keyfunc = lambda x: x
+        for i, j in groupby(xrange(n), key=keyfunc):
+            keyfunc.__dict__.setdefault('x',[]).append(j)
+
+    def test_ifilter(self):
+        a = []
+        self.makecycle(ifilter(lambda x:True, [a]*2), a)
+
+    def test_ifilterfalse(self):
+        a = []
+        self.makecycle(ifilterfalse(lambda x:False, a), a)
+
+    def test_izip(self):
+        a = []
+        self.makecycle(izip([a]*2, [a]*3), a)
+
+    def test_izip_longest(self):
+        a = []
+        self.makecycle(izip_longest([a]*2, [a]*3), a)
+        b = [a, None]
+        self.makecycle(izip_longest([a]*2, [a]*3, fillvalue=b), a)
+
+    def test_imap(self):
+        a = []
+        self.makecycle(imap(lambda x:x, [a]*2), a)
+
+    def test_islice(self):
+        a = []
+        self.makecycle(islice([a]*2, None), a)
+
+    def test_permutations(self):
+        a = []
+        self.makecycle(permutations([1,2,a,3], 3), a)
+
+    def test_product(self):
+        a = []
+        self.makecycle(product([1,2,a,3], repeat=3), a)
+
+    def test_repeat(self):
+        a = []
+        self.makecycle(repeat(a), a)
+
+    def test_starmap(self):
+        a = []
+        self.makecycle(starmap(lambda *t: t, [(a,a)]*2), a)
+
+    def test_takewhile(self):
+        a = []
+        self.makecycle(takewhile(bool, [1, 0, a, a]), a)
+
+def R(seqn):
+    'Regular generator'
+    for i in seqn:
+        yield i
+
+class G:
+    'Sequence using __getitem__'
+    def __init__(self, seqn):
+        self.seqn = seqn
+    def __getitem__(self, i):
+        return self.seqn[i]
+
+class I:
+    'Sequence using iterator protocol'
+    def __init__(self, seqn):
+        self.seqn = seqn
+        self.i = 0
+    def __iter__(self):
+        return self
+    def next(self):
+        if self.i >= len(self.seqn): raise StopIteration
+        v = self.seqn[self.i]
+        self.i += 1
+        return v
+
+class Ig:
+    'Sequence using iterator protocol defined with a generator'
+    def __init__(self, seqn):
+        self.seqn = seqn
+        self.i = 0
+    def __iter__(self):
+        for val in self.seqn:
+            yield val
+
+class X:
+    'Missing __getitem__ and __iter__'
+    def __init__(self, seqn):
+        self.seqn = seqn
+        self.i = 0
+    def next(self):
+        if self.i >= len(self.seqn): raise StopIteration
+        v = self.seqn[self.i]
+        self.i += 1
+        return v
+
+class N:
+    'Iterator missing next()'
+    def __init__(self, seqn):
+        self.seqn = seqn
+        self.i = 0
+    def __iter__(self):
+        return self
+
+class E:
+    'Test propagation of exceptions'
+    def __init__(self, seqn):
+        self.seqn = seqn
+        self.i = 0
+    def __iter__(self):
+        return self
+    def next(self):
+        3 // 0
+
+class S:
+    'Test immediate stop'
+    def __init__(self, seqn):
+        pass
+    def __iter__(self):
+        return self
+    def next(self):
+        raise StopIteration
+
+def L(seqn):
+    'Test multiple tiers of iterators'
+    return chain(imap(lambda x:x, R(Ig(G(seqn)))))
+
+
+class TestVariousIteratorArgs(unittest.TestCase):
+
+    def test_chain(self):
+        for s in ("123", "", range(1000), ('do', 1.2), xrange(2000,2200,5)):
+            for g in (G, I, Ig, S, L, R):
+                self.assertEqual(list(chain(g(s))), list(g(s)))
+                self.assertEqual(list(chain(g(s), g(s))), list(g(s))+list(g(s)))
+            self.assertRaises(TypeError, list, chain(X(s)))
+            self.assertRaises(TypeError, list, chain(N(s)))
+            self.assertRaises(ZeroDivisionError, list, chain(E(s)))
+
+    def test_compress(self):
+        for s in ("123", "", range(1000), ('do', 1.2), xrange(2000,2200,5)):
+            n = len(s)
+            for g in (G, I, Ig, S, L, R):
+                self.assertEqual(list(compress(g(s), repeat(1))), list(g(s)))
+            self.assertRaises(TypeError, compress, X(s), repeat(1))
+            self.assertRaises(TypeError, list, compress(N(s), repeat(1)))
+            self.assertRaises(ZeroDivisionError, list, compress(E(s), repeat(1)))
+
+    def test_product(self):
+        for s in ("123", "", range(1000), ('do', 1.2), xrange(2000,2200,5)):
+            self.assertRaises(TypeError, product, X(s))
+            self.assertRaises(TypeError, product, N(s))
+            self.assertRaises(ZeroDivisionError, product, E(s))
+
+    def test_cycle(self):
+        for s in ("123", "", range(1000), ('do', 1.2), xrange(2000,2200,5)):
+            for g in (G, I, Ig, S, L, R):
+                tgtlen = len(s) * 3
+                expected = list(g(s))*3
+                actual = list(islice(cycle(g(s)), tgtlen))
+                self.assertEqual(actual, expected)
+            self.assertRaises(TypeError, cycle, X(s))
+            self.assertRaises(TypeError, list, cycle(N(s)))
+            self.assertRaises(ZeroDivisionError, list, cycle(E(s)))
+
+    def test_groupby(self):
+        for s in (range(10), range(0), range(1000), (7,11), xrange(2000,2200,5)):
+            for g in (G, I, Ig, S, L, R):
+                self.assertEqual([k for k, sb in groupby(g(s))], list(g(s)))
+            self.assertRaises(TypeError, groupby, X(s))
+            self.assertRaises(TypeError, list, groupby(N(s)))
+            self.assertRaises(ZeroDivisionError, list, groupby(E(s)))
+
+    def test_ifilter(self):
+        for s in (range(10), range(0), range(1000), (7,11), xrange(2000,2200,5)):
+            for g in (G, I, Ig, S, L, R):
+                self.assertEqual(list(ifilter(isEven, g(s))), filter(isEven, g(s)))
+            self.assertRaises(TypeError, ifilter, isEven, X(s))
+            self.assertRaises(TypeError, list, ifilter(isEven, N(s)))
+            self.assertRaises(ZeroDivisionError, list, ifilter(isEven, E(s)))
+
+    def test_ifilterfalse(self):
+        for s in (range(10), range(0), range(1000), (7,11), xrange(2000,2200,5)):
+            for g in (G, I, Ig, S, L, R):
+                self.assertEqual(list(ifilterfalse(isEven, g(s))), filter(isOdd, g(s)))
+            self.assertRaises(TypeError, ifilterfalse, isEven, X(s))
+            self.assertRaises(TypeError, list, ifilterfalse(isEven, N(s)))
+            self.assertRaises(ZeroDivisionError, list, ifilterfalse(isEven, E(s)))
+
+    def test_izip(self):
+        for s in ("123", "", range(1000), ('do', 1.2), xrange(2000,2200,5)):
+            for g in (G, I, Ig, S, L, R):
+                self.assertEqual(list(izip(g(s))), zip(g(s)))
+                self.assertEqual(list(izip(g(s), g(s))), zip(g(s), g(s)))
+            self.assertRaises(TypeError, izip, X(s))
+            self.assertRaises(TypeError, list, izip(N(s)))
+            self.assertRaises(ZeroDivisionError, list, izip(E(s)))
+
+    def test_iziplongest(self):
+        for s in ("123", "", range(1000), ('do', 1.2), xrange(2000,2200,5)):
+            for g in (G, I, Ig, S, L, R):
+                self.assertEqual(list(izip_longest(g(s))), zip(g(s)))
+                self.assertEqual(list(izip_longest(g(s), g(s))), zip(g(s), g(s)))
+            self.assertRaises(TypeError, izip_longest, X(s))
+            self.assertRaises(TypeError, list, izip_longest(N(s)))
+            self.assertRaises(ZeroDivisionError, list, izip_longest(E(s)))
+
+    def test_imap(self):
+        for s in (range(10), range(0), range(100), (7,11), xrange(20,50,5)):
+            for g in (G, I, Ig, S, L, R):
+                self.assertEqual(list(imap(onearg, g(s))), map(onearg, g(s)))
+                self.assertEqual(list(imap(operator.pow, g(s), g(s))), map(operator.pow, g(s), g(s)))
+            self.assertRaises(TypeError, imap, onearg, X(s))
+            self.assertRaises(TypeError, list, imap(onearg, N(s)))
+            self.assertRaises(ZeroDivisionError, list, imap(onearg, E(s)))
+
+    def test_islice(self):
+        for s in ("12345", "", range(1000), ('do', 1.2), xrange(2000,2200,5)):
+            for g in (G, I, Ig, S, L, R):
+                self.assertEqual(list(islice(g(s),1,None,2)), list(g(s))[1::2])
+            self.assertRaises(TypeError, islice, X(s), 10)
+            self.assertRaises(TypeError, list, islice(N(s), 10))
+            self.assertRaises(ZeroDivisionError, list, islice(E(s), 10))
+
+    def test_starmap(self):
+        for s in (range(10), range(0), range(100), (7,11), xrange(20,50,5)):
+            for g in (G, I, Ig, S, L, R):
+                ss = zip(s, s)
+                self.assertEqual(list(starmap(operator.pow, g(ss))), map(operator.pow, g(s), g(s)))
+            self.assertRaises(TypeError, starmap, operator.pow, X(ss))
+            self.assertRaises(TypeError, list, starmap(operator.pow, N(ss)))
+            self.assertRaises(ZeroDivisionError, list, starmap(operator.pow, E(ss)))
+
+    def test_takewhile(self):
+        for s in (range(10), range(0), range(1000), (7,11), xrange(2000,2200,5)):
+            for g in (G, I, Ig, S, L, R):
+                tgt = []
+                for elem in g(s):
+                    if not isEven(elem): break
+                    tgt.append(elem)
+                self.assertEqual(list(takewhile(isEven, g(s))), tgt)
+            self.assertRaises(TypeError, takewhile, isEven, X(s))
+            self.assertRaises(TypeError, list, takewhile(isEven, N(s)))
+            self.assertRaises(ZeroDivisionError, list, takewhile(isEven, E(s)))
+
+    def test_dropwhile(self):
+        for s in (range(10), range(0), range(1000), (7,11), xrange(2000,2200,5)):
+            for g in (G, I, Ig, S, L, R):
+                tgt = []
+                for elem in g(s):
+                    if not tgt and isOdd(elem): continue
+                    tgt.append(elem)
+                self.assertEqual(list(dropwhile(isOdd, g(s))), tgt)
+            self.assertRaises(TypeError, dropwhile, isOdd, X(s))
+            self.assertRaises(TypeError, list, dropwhile(isOdd, N(s)))
+            self.assertRaises(ZeroDivisionError, list, dropwhile(isOdd, E(s)))
+
+    def test_tee(self):
+        for s in ("123", "", range(1000), ('do', 1.2), xrange(2000,2200,5)):
+            for g in (G, I, Ig, S, L, R):
+                it1, it2 = tee(g(s))
+                self.assertEqual(list(it1), list(g(s)))
+                self.assertEqual(list(it2), list(g(s)))
+            self.assertRaises(TypeError, tee, X(s))
+            self.assertRaises(TypeError, list, tee(N(s))[0])
+            self.assertRaises(ZeroDivisionError, list, tee(E(s))[0])
+
+class LengthTransparency(unittest.TestCase):
+
+    def test_repeat(self):
+        from test.test_iterlen import len
+        self.assertEqual(len(repeat(None, 50)), 50)
+        self.assertRaises(TypeError, len, repeat(None))
+
+class RegressionTests(unittest.TestCase):
+
+    def test_sf_793826(self):
+        # Fix Armin Rigo's successful efforts to wreak havoc
+
+        def mutatingtuple(tuple1, f, tuple2):
+            # this builds a tuple t which is a copy of tuple1,
+            # then calls f(t), then mutates t to be equal to tuple2
+            # (needs len(tuple1) == len(tuple2)).
+            def g(value, first=[1]):
+                if first:
+                    del first[:]
+                    f(z.next())
+                return value
+            items = list(tuple2)
+            items[1:1] = list(tuple1)
+            gen = imap(g, items)
+            z = izip(*[gen]*len(tuple1))
+            z.next()
+
+        def f(t):
+            global T
+            T = t
+            first[:] = list(T)
+
+        first = []
+        mutatingtuple((1,2,3), f, (4,5,6))
+        second = list(T)
+        self.assertEqual(first, second)
+
+
+    def test_sf_950057(self):
+        # Make sure that chain() and cycle() catch exceptions immediately
+        # rather than when shifting between input sources
+
+        def gen1():
+            hist.append(0)
+            yield 1
+            hist.append(1)
+            raise AssertionError
+            hist.append(2)
+
+        def gen2(x):
+            hist.append(3)
+            yield 2
+            hist.append(4)
+            if x:
+                raise StopIteration
+
+        hist = []
+        self.assertRaises(AssertionError, list, chain(gen1(), gen2(False)))
+        self.assertEqual(hist, [0,1])
+
+        hist = []
+        self.assertRaises(AssertionError, list, chain(gen1(), gen2(True)))
+        self.assertEqual(hist, [0,1])
+
+        hist = []
+        self.assertRaises(AssertionError, list, cycle(gen1()))
+        self.assertEqual(hist, [0,1])
+
+class SubclassWithKwargsTest(unittest.TestCase):
+    def test_keywords_in_subclass(self):
+        # count is not subclassable...
+        for cls in (repeat, izip, ifilter, ifilterfalse, chain, imap,
+                    starmap, islice, takewhile, dropwhile, cycle, compress):
+            class Subclass(cls):
+                def __init__(self, newarg=None, *args):
+                    cls.__init__(self, *args)
+            try:
+                Subclass(newarg=1)
+            except TypeError, err:
+                # we expect type errors because of wrong argument count
+                self.assertNotIn("does not take keyword arguments", err.args[0])
+
+
+libreftest = """ Doctest for examples in the library reference: libitertools.tex
+
+
+>>> amounts = [120.15, 764.05, 823.14]
+>>> for checknum, amount in izip(count(1200), amounts):
+...     print 'Check %d is for $%.2f' % (checknum, amount)
+...
+Check 1200 is for $120.15
+Check 1201 is for $764.05
+Check 1202 is for $823.14
+
+>>> import operator
+>>> for cube in imap(operator.pow, xrange(1,4), repeat(3)):
+...    print cube
+...
+1
+8
+27
+
+>>> reportlines = ['EuroPython', 'Roster', '', 'alex', '', 'laura', '', 'martin', '', 'walter', '', 'samuele']
+>>> for name in islice(reportlines, 3, None, 2):
+...    print name.title()
+...
+Alex
+Laura
+Martin
+Walter
+Samuele
+
+>>> from operator import itemgetter
+>>> d = dict(a=1, b=2, c=1, d=2, e=1, f=2, g=3)
+>>> di = sorted(sorted(d.iteritems()), key=itemgetter(1))
+>>> for k, g in groupby(di, itemgetter(1)):
+...     print k, map(itemgetter(0), g)
+...
+1 ['a', 'c', 'e']
+2 ['b', 'd', 'f']
+3 ['g']
+
+# Find runs of consecutive numbers using groupby.  The key to the solution
+# is differencing with a range so that consecutive numbers all appear in
+# same group.
+>>> data = [ 1,  4,5,6, 10, 15,16,17,18, 22, 25,26,27,28]
+>>> for k, g in groupby(enumerate(data), lambda t:t[0]-t[1]):
+...     print map(operator.itemgetter(1), g)
+...
+[1]
+[4, 5, 6]
+[10]
+[15, 16, 17, 18]
+[22]
+[25, 26, 27, 28]
+
+>>> def take(n, iterable):
+...     "Return first n items of the iterable as a list"
+...     return list(islice(iterable, n))
+
+>>> def enumerate(iterable, start=0):
+...     return izip(count(start), iterable)
+
+>>> def tabulate(function, start=0):
+...     "Return function(0), function(1), ..."
+...     return imap(function, count(start))
+
+>>> def nth(iterable, n, default=None):
+...     "Returns the nth item or a default value"
+...     return next(islice(iterable, n, None), default)
+
+>>> def quantify(iterable, pred=bool):
+...     "Count how many times the predicate is true"
+...     return sum(imap(pred, iterable))
+
+>>> def padnone(iterable):
+...     "Returns the sequence elements and then returns None indefinitely"
+...     return chain(iterable, repeat(None))
+
+>>> def ncycles(iterable, n):
+...     "Returns the seqeuence elements n times"
+...     return chain(*repeat(iterable, n))
+
+>>> def dotproduct(vec1, vec2):
+...     return sum(imap(operator.mul, vec1, vec2))
+
+>>> def flatten(listOfLists):
+...     return list(chain.from_iterable(listOfLists))
+
+>>> def repeatfunc(func, times=None, *args):
+...     "Repeat calls to func with specified arguments."
+...     "   Example:  repeatfunc(random.random)"
+...     if times is None:
+...         return starmap(func, repeat(args))
+...     else:
+...         return starmap(func, repeat(args, times))
+
+>>> def pairwise(iterable):
+...     "s -> (s0,s1), (s1,s2), (s2, s3), ..."
+...     a, b = tee(iterable)
+...     for elem in b:
+...         break
+...     return izip(a, b)
+
+>>> def grouper(n, iterable, fillvalue=None):
+...     "grouper(3, 'ABCDEFG', 'x') --> ABC DEF Gxx"
+...     args = [iter(iterable)] * n
+...     return izip_longest(fillvalue=fillvalue, *args)
+
+>>> def roundrobin(*iterables):
+...     "roundrobin('ABC', 'D', 'EF') --> A D E B F C"
+...     # Recipe credited to George Sakkis
+...     pending = len(iterables)
+...     nexts = cycle(iter(it).next for it in iterables)
+...     while pending:
+...         try:
+...             for next in nexts:
+...                 yield next()
+...         except StopIteration:
+...             pending -= 1
+...             nexts = cycle(islice(nexts, pending))
+
+>>> def powerset(iterable):
+...     "powerset([1,2,3]) --> () (1,) (2,) (3,) (1,2) (1,3) (2,3) (1,2,3)"
+...     s = list(iterable)
+...     return chain.from_iterable(combinations(s, r) for r in range(len(s)+1))
+
+>>> def unique_everseen(iterable, key=None):
+...     "List unique elements, preserving order. Remember all elements ever seen."
+...     # unique_everseen('AAAABBBCCDAABBB') --> A B C D
+...     # unique_everseen('ABBCcAD', str.lower) --> A B C D
+...     seen = set()
+...     seen_add = seen.add
+...     if key is None:
+...         for element in iterable:
+...             if element not in seen:
+...                 seen_add(element)
+...                 yield element
+...     else:
+...         for element in iterable:
+...             k = key(element)
+...             if k not in seen:
+...                 seen_add(k)
+...                 yield element
+
+>>> def unique_justseen(iterable, key=None):
+...     "List unique elements, preserving order. Remember only the element just seen."
+...     # unique_justseen('AAAABBBCCDAABBB') --> A B C D A B
+...     # unique_justseen('ABBCcAD', str.lower) --> A B C A D
+...     return imap(next, imap(itemgetter(1), groupby(iterable, key)))
+
+This is not part of the examples but it tests to make sure the definitions
+perform as purported.
+
+>>> take(10, count())
+[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
+
+>>> list(enumerate('abc'))
+[(0, 'a'), (1, 'b'), (2, 'c')]
+
+>>> list(islice(tabulate(lambda x: 2*x), 4))
+[0, 2, 4, 6]
+
+>>> nth('abcde', 3)
+'d'
+
+>>> nth('abcde', 9) is None
+True
+
+>>> quantify(xrange(99), lambda x: x%2==0)
+50
+
+>>> a = [[1, 2, 3], [4, 5, 6]]
+>>> flatten(a)
+[1, 2, 3, 4, 5, 6]
+
+>>> list(repeatfunc(pow, 5, 2, 3))
+[8, 8, 8, 8, 8]
+
+>>> import random
+>>> take(5, imap(int, repeatfunc(random.random)))
+[0, 0, 0, 0, 0]
+
+>>> list(pairwise('abcd'))
+[('a', 'b'), ('b', 'c'), ('c', 'd')]
+
+>>> list(pairwise([]))
+[]
+
+>>> list(pairwise('a'))
+[]
+
+>>> list(islice(padnone('abc'), 0, 6))
+['a', 'b', 'c', None, None, None]
+
+>>> list(ncycles('abc', 3))
+['a', 'b', 'c', 'a', 'b', 'c', 'a', 'b', 'c']
+
+>>> dotproduct([1,2,3], [4,5,6])
+32
+
+>>> list(grouper(3, 'abcdefg', 'x'))
+[('a', 'b', 'c'), ('d', 'e', 'f'), ('g', 'x', 'x')]
+
+>>> list(roundrobin('abc', 'd', 'ef'))
+['a', 'd', 'e', 'b', 'f', 'c']
+
+>>> list(powerset([1,2,3]))
+[(), (1,), (2,), (3,), (1, 2), (1, 3), (2, 3), (1, 2, 3)]
+
+>>> all(len(list(powerset(range(n)))) == 2**n for n in range(18))
+True
+
+>>> list(powerset('abcde')) == sorted(sorted(set(powerset('abcde'))), key=len)
+True
+
+>>> list(unique_everseen('AAAABBBCCDAABBB'))
+['A', 'B', 'C', 'D']
+
+>>> list(unique_everseen('ABBCcAD', str.lower))
+['A', 'B', 'C', 'D']
+
+>>> list(unique_justseen('AAAABBBCCDAABBB'))
+['A', 'B', 'C', 'D', 'A', 'B']
+
+>>> list(unique_justseen('ABBCcAD', str.lower))
+['A', 'B', 'C', 'A', 'D']
+
+"""
+
+__test__ = {'libreftest' : libreftest}
+
+def test_main(verbose=None):
+    test_classes = (TestBasicOps, TestVariousIteratorArgs, TestGC,
+                    RegressionTests, LengthTransparency,
+                    SubclassWithKwargsTest, TestExamples)
+    test_support.run_unittest(*test_classes)
+
+    # verify reference counting
+    if verbose and hasattr(sys, "gettotalrefcount"):
+        import gc
+        counts = [None] * 5
+        for i in xrange(len(counts)):
+            test_support.run_unittest(*test_classes)
+            gc.collect()
+            counts[i] = sys.gettotalrefcount()
+        print counts
+
+    # doctest the examples in the library reference
+    test_support.run_doctest(sys.modules[__name__], verbose)
+
+if __name__ == "__main__":
+    test_main(verbose=True)