(self)
| 223 | self.assertEqual(list(islice(chain.from_iterable(repeat(range(5))), 2)), [0, 1]) |
| 224 | |
| 225 | def test_combinations(self): |
| 226 | self.assertRaises(TypeError, combinations, 'abc') # missing r argument |
| 227 | self.assertRaises(TypeError, combinations, 'abc', 2, 1) # too many arguments |
| 228 | self.assertRaises(TypeError, combinations, None) # pool is not iterable |
| 229 | self.assertRaises(ValueError, combinations, 'abc', -2) # r is negative |
| 230 | |
| 231 | def combinations1(iterable, r): |
| 232 | 'Pure python version shown in the docs' |
| 233 | pool = tuple(iterable) |
| 234 | n = len(pool) |
| 235 | if r > n: |
| 236 | return |
| 237 | indices = list(range(r)) |
| 238 | yield tuple(pool[i] for i in indices) |
| 239 | while 1: |
| 240 | for i in reversed(range(r)): |
| 241 | if indices[i] != i + n - r: |
| 242 | break |
| 243 | else: |
| 244 | return |
| 245 | indices[i] += 1 |
| 246 | for j in range(i+1, r): |
| 247 | indices[j] = indices[j-1] + 1 |
| 248 | yield tuple(pool[i] for i in indices) |
| 249 | |
| 250 | def combinations2(iterable, r): |
| 251 | 'Pure python version shown in the docs' |
| 252 | pool = tuple(iterable) |
| 253 | n = len(pool) |
| 254 | for indices in permutations(range(n), r): |
| 255 | if sorted(indices) == list(indices): |
| 256 | yield tuple(pool[i] for i in indices) |
| 257 | |
| 258 | def combinations3(iterable, r): |
| 259 | 'Pure python version from cwr()' |
| 260 | pool = tuple(iterable) |
| 261 | n = len(pool) |
| 262 | for indices in combinations_with_replacement(range(n), r): |
| 263 | if len(set(indices)) == r: |
| 264 | yield tuple(pool[i] for i in indices) |
| 265 | |
| 266 | for n in range(7): |
| 267 | values = [5*x-12 for x in range(n)] |
| 268 | for r in range(n+2): |
| 269 | result = list(combinations(values, r)) |
| 270 | self.assertEqual(len(result), 0 if r>n else fact(n) / fact(r) / fact(n-r)) # right number of combs |
| 271 | self.assertEqual(len(result), len(set(result))) # no repeats |
| 272 | self.assertEqual(result, sorted(result)) # lexicographic order |
| 273 | for c in result: |
| 274 | self.assertEqual(len(c), r) # r-length combinations |
| 275 | self.assertEqual(len(set(c)), r) # no duplicate elements |
| 276 | self.assertEqual(list(c), sorted(c)) # keep original ordering |
| 277 | self.assertTrue(all(e in values for e in c)) # elements taken from input iterable |
| 278 | self.assertEqual(list(c), |
| 279 | [e for e in values if e in c]) # comb is a subsequence of the input iterable |
| 280 | self.assertEqual(result, list(combinations1(values, r))) # matches first pure python version |
| 281 | self.assertEqual(result, list(combinations2(values, r))) # matches second pure python version |
| 282 | self.assertEqual(result, list(combinations3(values, r))) # matches second pure python version |
nothing calls this directly
no test coverage detected