text: 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.assertEqual(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.assertEqual(len(prod), n**r)
                  self.assertEqual(len(cwr), (fact(n+r-1) // fact(r) // fact(n-1)) if n else (not r))
                  self.assertEqual(len(perm), 0 if r>n else fact(n) // fact(n-r))
                  self.assertEqual(len(comb), 0 if r>n else fact(n) // fact(r) // fact(n-r))
  
                  # Check lexicographic order without repeated tuples
                  self.assertEqual(prod, sorted(set(prod)))
                  self.assertEqual(cwr, sorted(set(cwr)))
                  self.assertEqual(perm, sorted(set(perm)))
                  self.assertEqual(comb, sorted(set(comb)))
  
                  # Check interrelationships
                  self.assertEqual(cwr, [t for t in prod if sorted(t)==list(t)]) # cwr: prods which are sorted
                  self.assertEqual(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)
  