Add itertools.combinations().
diff --git a/Lib/test/test_itertools.py b/Lib/test/test_itertools.py
index dc9081e..9868325 100644
--- a/Lib/test/test_itertools.py
+++ b/Lib/test/test_itertools.py
@@ -40,6 +40,10 @@
'Convenience function for partially consuming a long of infinite iterable'
return list(islice(seq, n))
+def fact(n):
+ 'Factorial'
+ return reduce(operator.mul, range(1, n+1), 1)
+
class TestBasicOps(unittest.TestCase):
def test_chain(self):
self.assertEqual(list(chain('abc', 'def')), list('abcdef'))
@@ -48,6 +52,26 @@
self.assertEqual(take(4, chain('abc', 'def')), list('abcd'))
self.assertRaises(TypeError, chain, 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(ValueError, combinations, 'abc', -2) # r is negative
+ self.assertRaises(ValueError, combinations, 'abc', 32) # r is too big
+ self.assertEqual(list(combinations(range(4), 3)),
+ [(0,1,2), (0,1,3), (0,2,3), (1,2,3)])
+ for n in range(6):
+ values = [5*x-12 for x in range(n)]
+ for r in range(n+1):
+ result = list(combinations(values, r))
+ self.assertEqual(len(result), 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.assert_(all(e in values for e in c)) # elements taken from input iterable
+
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)])