import unittest from test import test_support from itertools import * import sys import operator import random 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)) class TestBasicOps(unittest.TestCase): def test_chain(self): self.assertEqual(list(chain('abc', 'def')), list('abcdef')) self.assertEqual(list(chain('abc')), list('abc')) self.assertEqual(list(chain('')), []) self.assertEqual(take(4, chain('abc', 'def')), list('abcd')) self.assertRaises(TypeError, chain, 2, 3) 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.assertRaises(TypeError, count, 2, 3) self.assertRaises(TypeError, count, 'a') c = count(sys.maxint-2) # verify that rollover doesn't crash c.next(); c.next(); c.next(); c.next(); c.next() 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) # 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(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(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_repeat(self): 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') 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.assertRaises(TypeError, list, starmap(operator.pow, [[4,5]])) 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), 2, None)), range(2, 10)) self.assertEqual(list(islice(xrange(10), 1, None, 2)), range(1, 10, 2)) # 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, sys.maxint))), 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) 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)) # tee pass-through to copyable iterator a, b = tee('abc') c, d = tee(a) self.assert_(a is c) 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 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_cycle(self): a = [] self.makecycle(cycle([a]*2), a) 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_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_starmap(self): a = [] self.makecycle(starmap(lambda *t: t, [(a,a)]*2), 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, chain, X(s)) self.assertRaises(TypeError, list, chain(N(s))) self.assertRaises(ZeroDivisionError, list, chain(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_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): 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) 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(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 (i,x):i-x): ... print map(operator.itemgetter(1), g) ... [1] [4, 5, 6] [10] [15, 16, 17, 18] [22] [25, 26, 27, 28] >>> def take(n, seq): ... return list(islice(seq, n)) >>> def enumerate(iterable): ... return izip(count(), iterable) >>> def tabulate(function): ... "Return function(0), function(1), ..." ... return imap(function, count()) >>> def iteritems(mapping): ... return izip(mapping.iterkeys(), mapping.itervalues()) >>> def nth(iterable, n): ... "Returns the nth item" ... return list(islice(iterable, n, n+1)) >>> def all(seq, pred=bool): ... "Returns True if pred(x) is True for every element in the iterable" ... return False not in imap(pred, seq) >>> def any(seq, pred=bool): ... "Returns True if pred(x) is True for at least one element in the iterable" ... return True in imap(pred, seq) >>> def no(seq, pred=bool): ... "Returns True if pred(x) is False for every element in the iterable" ... return True not in imap(pred, seq) >>> def quantify(seq, pred=bool): ... "Count how many times the predicate is True in the sequence" ... return sum(imap(pred, seq)) >>> def padnone(seq): ... "Returns the sequence elements and then returns None indefinitely" ... return chain(seq, repeat(None)) >>> def ncycles(seq, n): ... "Returns the sequence elements n times" ... return chain(*repeat(seq, n)) >>> def dotproduct(vec1, vec2): ... return sum(imap(operator.mul, vec1, vec2)) >>> def flatten(listOfLists): ... return list(chain(*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) ... try: ... b.next() ... except StopIteration: ... pass ... return izip(a, b) This is not part of the examples but it tests to make sure the definitions perform as purported. >>> 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'] >>> all([2, 4, 6, 8], lambda x: x%2==0) True >>> all([2, 3, 6, 8], lambda x: x%2==0) False >>> any([2, 4, 6, 8], lambda x: x%2==0) True >>> any([1, 3, 5, 9], lambda x: x%2==0,) False >>> no([1, 3, 5, 9], lambda x: x%2==0) True >>> no([1, 2, 5, 9], lambda x: x%2==0) False >>> 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 """ __test__ = {'libreftest' : libreftest} def test_main(verbose=None): test_classes = (TestBasicOps, TestVariousIteratorArgs, TestGC, RegressionTests, LengthTransparency) 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)