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Add itertools.combinations().

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This commit is contained in:
Raymond Hettinger 2008-02-26 23:40:50 +00:00
parent 3ef2063ec8
commit 93e804da9c
4 changed files with 266 additions and 16 deletions
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24
Lib/test/test_itertools.py
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@ -40,6 +40,10 @@ def take(n, seq):
'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 @@ def test_chain(self):
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)])