Antoine Pitrou | 796564c | 2013-07-30 19:59:21 +0200 | [diff] [blame] | 1 | import gc |
| 2 | import sys |
| 3 | import unittest |
| 4 | import weakref |
| 5 | |
| 6 | from test import support |
| 7 | |
| 8 | |
| 9 | class FinalizationTest(unittest.TestCase): |
| 10 | |
| 11 | def test_frame_resurrect(self): |
| 12 | # A generator frame can be resurrected by a generator's finalization. |
| 13 | def gen(): |
| 14 | nonlocal frame |
| 15 | try: |
| 16 | yield |
| 17 | finally: |
| 18 | frame = sys._getframe() |
| 19 | |
| 20 | g = gen() |
| 21 | wr = weakref.ref(g) |
| 22 | next(g) |
| 23 | del g |
| 24 | support.gc_collect() |
| 25 | self.assertIs(wr(), None) |
| 26 | self.assertTrue(frame) |
| 27 | del frame |
| 28 | support.gc_collect() |
| 29 | |
| 30 | def test_refcycle(self): |
| 31 | # A generator caught in a refcycle gets finalized anyway. |
| 32 | old_garbage = gc.garbage[:] |
| 33 | finalized = False |
| 34 | def gen(): |
| 35 | nonlocal finalized |
| 36 | try: |
| 37 | g = yield |
| 38 | yield 1 |
| 39 | finally: |
| 40 | finalized = True |
| 41 | |
| 42 | g = gen() |
| 43 | next(g) |
| 44 | g.send(g) |
| 45 | self.assertGreater(sys.getrefcount(g), 2) |
| 46 | self.assertFalse(finalized) |
| 47 | del g |
| 48 | support.gc_collect() |
| 49 | self.assertTrue(finalized) |
| 50 | self.assertEqual(gc.garbage, old_garbage) |
| 51 | |
| 52 | |
Victor Stinner | 40ee301 | 2014-06-16 15:59:28 +0200 | [diff] [blame] | 53 | class GeneratorTest(unittest.TestCase): |
| 54 | |
| 55 | def test_name(self): |
| 56 | def func(): |
| 57 | yield 1 |
| 58 | |
| 59 | # check generator names |
| 60 | gen = func() |
| 61 | self.assertEqual(gen.__name__, "func") |
| 62 | self.assertEqual(gen.__qualname__, |
| 63 | "GeneratorTest.test_name.<locals>.func") |
| 64 | |
| 65 | # modify generator names |
| 66 | gen.__name__ = "name" |
| 67 | gen.__qualname__ = "qualname" |
| 68 | self.assertEqual(gen.__name__, "name") |
| 69 | self.assertEqual(gen.__qualname__, "qualname") |
| 70 | |
| 71 | # generator names must be a string and cannot be deleted |
| 72 | self.assertRaises(TypeError, setattr, gen, '__name__', 123) |
| 73 | self.assertRaises(TypeError, setattr, gen, '__qualname__', 123) |
| 74 | self.assertRaises(TypeError, delattr, gen, '__name__') |
| 75 | self.assertRaises(TypeError, delattr, gen, '__qualname__') |
| 76 | |
| 77 | # modify names of the function creating the generator |
| 78 | func.__qualname__ = "func_qualname" |
| 79 | func.__name__ = "func_name" |
| 80 | gen = func() |
| 81 | self.assertEqual(gen.__name__, "func_name") |
| 82 | self.assertEqual(gen.__qualname__, "func_qualname") |
| 83 | |
| 84 | # unnamed generator |
| 85 | gen = (x for x in range(10)) |
| 86 | self.assertEqual(gen.__name__, |
| 87 | "<genexpr>") |
| 88 | self.assertEqual(gen.__qualname__, |
| 89 | "GeneratorTest.test_name.<locals>.<genexpr>") |
| 90 | |
| 91 | |
Tim Peters | 6ba5f79 | 2001-06-23 20:45:43 +0000 | [diff] [blame] | 92 | tutorial_tests = """ |
Tim Peters | 1def351 | 2001-06-23 20:27:04 +0000 | [diff] [blame] | 93 | Let's try a simple generator: |
| 94 | |
| 95 | >>> def f(): |
| 96 | ... yield 1 |
| 97 | ... yield 2 |
| 98 | |
Tim Peters | b9e9ff1 | 2001-06-24 03:44:52 +0000 | [diff] [blame] | 99 | >>> for i in f(): |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 100 | ... print(i) |
Tim Peters | b9e9ff1 | 2001-06-24 03:44:52 +0000 | [diff] [blame] | 101 | 1 |
| 102 | 2 |
Tim Peters | 1def351 | 2001-06-23 20:27:04 +0000 | [diff] [blame] | 103 | >>> g = f() |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 104 | >>> next(g) |
Tim Peters | 1def351 | 2001-06-23 20:27:04 +0000 | [diff] [blame] | 105 | 1 |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 106 | >>> next(g) |
Tim Peters | 1def351 | 2001-06-23 20:27:04 +0000 | [diff] [blame] | 107 | 2 |
Tim Peters | ea2e97a | 2001-06-24 07:10:02 +0000 | [diff] [blame] | 108 | |
Tim Peters | 2106ef0 | 2001-06-25 01:30:12 +0000 | [diff] [blame] | 109 | "Falling off the end" stops the generator: |
Tim Peters | ea2e97a | 2001-06-24 07:10:02 +0000 | [diff] [blame] | 110 | |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 111 | >>> next(g) |
Tim Peters | 1def351 | 2001-06-23 20:27:04 +0000 | [diff] [blame] | 112 | Traceback (most recent call last): |
| 113 | File "<stdin>", line 1, in ? |
| 114 | File "<stdin>", line 2, in g |
| 115 | StopIteration |
| 116 | |
Tim Peters | ea2e97a | 2001-06-24 07:10:02 +0000 | [diff] [blame] | 117 | "return" also stops the generator: |
Tim Peters | 1def351 | 2001-06-23 20:27:04 +0000 | [diff] [blame] | 118 | |
| 119 | >>> def f(): |
| 120 | ... yield 1 |
| 121 | ... return |
| 122 | ... yield 2 # never reached |
| 123 | ... |
| 124 | >>> g = f() |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 125 | >>> next(g) |
Tim Peters | 1def351 | 2001-06-23 20:27:04 +0000 | [diff] [blame] | 126 | 1 |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 127 | >>> next(g) |
Tim Peters | 1def351 | 2001-06-23 20:27:04 +0000 | [diff] [blame] | 128 | Traceback (most recent call last): |
| 129 | File "<stdin>", line 1, in ? |
| 130 | File "<stdin>", line 3, in f |
| 131 | StopIteration |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 132 | >>> next(g) # once stopped, can't be resumed |
Tim Peters | 1def351 | 2001-06-23 20:27:04 +0000 | [diff] [blame] | 133 | Traceback (most recent call last): |
| 134 | File "<stdin>", line 1, in ? |
| 135 | StopIteration |
| 136 | |
| 137 | "raise StopIteration" stops the generator too: |
| 138 | |
| 139 | >>> def f(): |
| 140 | ... yield 1 |
Tim Peters | 3446365 | 2001-07-12 22:43:41 +0000 | [diff] [blame] | 141 | ... raise StopIteration |
Tim Peters | 1def351 | 2001-06-23 20:27:04 +0000 | [diff] [blame] | 142 | ... yield 2 # never reached |
| 143 | ... |
| 144 | >>> g = f() |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 145 | >>> next(g) |
Tim Peters | 1def351 | 2001-06-23 20:27:04 +0000 | [diff] [blame] | 146 | 1 |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 147 | >>> next(g) |
Tim Peters | 1def351 | 2001-06-23 20:27:04 +0000 | [diff] [blame] | 148 | Traceback (most recent call last): |
| 149 | File "<stdin>", line 1, in ? |
| 150 | StopIteration |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 151 | >>> next(g) |
Tim Peters | 1def351 | 2001-06-23 20:27:04 +0000 | [diff] [blame] | 152 | Traceback (most recent call last): |
| 153 | File "<stdin>", line 1, in ? |
| 154 | StopIteration |
| 155 | |
| 156 | However, they are not exactly equivalent: |
| 157 | |
| 158 | >>> def g1(): |
| 159 | ... try: |
| 160 | ... return |
| 161 | ... except: |
| 162 | ... yield 1 |
| 163 | ... |
| 164 | >>> list(g1()) |
| 165 | [] |
| 166 | |
| 167 | >>> def g2(): |
| 168 | ... try: |
| 169 | ... raise StopIteration |
| 170 | ... except: |
| 171 | ... yield 42 |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 172 | >>> print(list(g2())) |
Tim Peters | 1def351 | 2001-06-23 20:27:04 +0000 | [diff] [blame] | 173 | [42] |
| 174 | |
| 175 | This may be surprising at first: |
| 176 | |
| 177 | >>> def g3(): |
| 178 | ... try: |
| 179 | ... return |
| 180 | ... finally: |
| 181 | ... yield 1 |
| 182 | ... |
| 183 | >>> list(g3()) |
| 184 | [1] |
| 185 | |
| 186 | Let's create an alternate range() function implemented as a generator: |
| 187 | |
| 188 | >>> def yrange(n): |
| 189 | ... for i in range(n): |
| 190 | ... yield i |
| 191 | ... |
| 192 | >>> list(yrange(5)) |
| 193 | [0, 1, 2, 3, 4] |
| 194 | |
| 195 | Generators always return to the most recent caller: |
| 196 | |
| 197 | >>> def creator(): |
| 198 | ... r = yrange(5) |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 199 | ... print("creator", next(r)) |
Tim Peters | 1def351 | 2001-06-23 20:27:04 +0000 | [diff] [blame] | 200 | ... return r |
Guido van Rossum | c420b2f | 2007-02-09 22:09:01 +0000 | [diff] [blame] | 201 | ... |
Tim Peters | 1def351 | 2001-06-23 20:27:04 +0000 | [diff] [blame] | 202 | >>> def caller(): |
| 203 | ... r = creator() |
| 204 | ... for i in r: |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 205 | ... print("caller", i) |
Guido van Rossum | c420b2f | 2007-02-09 22:09:01 +0000 | [diff] [blame] | 206 | ... |
Tim Peters | 1def351 | 2001-06-23 20:27:04 +0000 | [diff] [blame] | 207 | >>> caller() |
| 208 | creator 0 |
| 209 | caller 1 |
| 210 | caller 2 |
| 211 | caller 3 |
| 212 | caller 4 |
| 213 | |
| 214 | Generators can call other generators: |
| 215 | |
| 216 | >>> def zrange(n): |
| 217 | ... for i in yrange(n): |
| 218 | ... yield i |
| 219 | ... |
| 220 | >>> list(zrange(5)) |
| 221 | [0, 1, 2, 3, 4] |
| 222 | |
| 223 | """ |
| 224 | |
Tim Peters | 6ba5f79 | 2001-06-23 20:45:43 +0000 | [diff] [blame] | 225 | # The examples from PEP 255. |
| 226 | |
| 227 | pep_tests = """ |
| 228 | |
Tim Peters | e561463 | 2001-08-15 04:41:19 +0000 | [diff] [blame] | 229 | Specification: Yield |
| 230 | |
| 231 | Restriction: A generator cannot be resumed while it is actively |
| 232 | running: |
| 233 | |
| 234 | >>> def g(): |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 235 | ... i = next(me) |
Tim Peters | e561463 | 2001-08-15 04:41:19 +0000 | [diff] [blame] | 236 | ... yield i |
| 237 | >>> me = g() |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 238 | >>> next(me) |
Tim Peters | e561463 | 2001-08-15 04:41:19 +0000 | [diff] [blame] | 239 | Traceback (most recent call last): |
| 240 | ... |
| 241 | File "<string>", line 2, in g |
| 242 | ValueError: generator already executing |
| 243 | |
Tim Peters | 6ba5f79 | 2001-06-23 20:45:43 +0000 | [diff] [blame] | 244 | Specification: Return |
| 245 | |
| 246 | Note that return isn't always equivalent to raising StopIteration: the |
| 247 | difference lies in how enclosing try/except constructs are treated. |
| 248 | For example, |
| 249 | |
| 250 | >>> def f1(): |
| 251 | ... try: |
| 252 | ... return |
| 253 | ... except: |
| 254 | ... yield 1 |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 255 | >>> print(list(f1())) |
Tim Peters | 6ba5f79 | 2001-06-23 20:45:43 +0000 | [diff] [blame] | 256 | [] |
| 257 | |
| 258 | because, as in any function, return simply exits, but |
| 259 | |
| 260 | >>> def f2(): |
| 261 | ... try: |
| 262 | ... raise StopIteration |
| 263 | ... except: |
| 264 | ... yield 42 |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 265 | >>> print(list(f2())) |
Tim Peters | 6ba5f79 | 2001-06-23 20:45:43 +0000 | [diff] [blame] | 266 | [42] |
| 267 | |
| 268 | because StopIteration is captured by a bare "except", as is any |
| 269 | exception. |
| 270 | |
| 271 | Specification: Generators and Exception Propagation |
| 272 | |
| 273 | >>> def f(): |
Tim Peters | 3caca23 | 2001-12-06 06:23:26 +0000 | [diff] [blame] | 274 | ... return 1//0 |
Tim Peters | 6ba5f79 | 2001-06-23 20:45:43 +0000 | [diff] [blame] | 275 | >>> def g(): |
| 276 | ... yield f() # the zero division exception propagates |
| 277 | ... yield 42 # and we'll never get here |
| 278 | >>> k = g() |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 279 | >>> next(k) |
Tim Peters | 6ba5f79 | 2001-06-23 20:45:43 +0000 | [diff] [blame] | 280 | Traceback (most recent call last): |
| 281 | File "<stdin>", line 1, in ? |
| 282 | File "<stdin>", line 2, in g |
| 283 | File "<stdin>", line 2, in f |
| 284 | ZeroDivisionError: integer division or modulo by zero |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 285 | >>> next(k) # and the generator cannot be resumed |
Tim Peters | 6ba5f79 | 2001-06-23 20:45:43 +0000 | [diff] [blame] | 286 | Traceback (most recent call last): |
| 287 | File "<stdin>", line 1, in ? |
| 288 | StopIteration |
| 289 | >>> |
| 290 | |
| 291 | Specification: Try/Except/Finally |
| 292 | |
| 293 | >>> def f(): |
| 294 | ... try: |
| 295 | ... yield 1 |
| 296 | ... try: |
| 297 | ... yield 2 |
Tim Peters | 3caca23 | 2001-12-06 06:23:26 +0000 | [diff] [blame] | 298 | ... 1//0 |
Tim Peters | 6ba5f79 | 2001-06-23 20:45:43 +0000 | [diff] [blame] | 299 | ... yield 3 # never get here |
| 300 | ... except ZeroDivisionError: |
| 301 | ... yield 4 |
| 302 | ... yield 5 |
| 303 | ... raise |
| 304 | ... except: |
| 305 | ... yield 6 |
| 306 | ... yield 7 # the "raise" above stops this |
| 307 | ... except: |
| 308 | ... yield 8 |
| 309 | ... yield 9 |
| 310 | ... try: |
| 311 | ... x = 12 |
| 312 | ... finally: |
| 313 | ... yield 10 |
| 314 | ... yield 11 |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 315 | >>> print(list(f())) |
Tim Peters | 6ba5f79 | 2001-06-23 20:45:43 +0000 | [diff] [blame] | 316 | [1, 2, 4, 5, 8, 9, 10, 11] |
| 317 | >>> |
| 318 | |
Tim Peters | 6ba5f79 | 2001-06-23 20:45:43 +0000 | [diff] [blame] | 319 | Guido's binary tree example. |
| 320 | |
| 321 | >>> # A binary tree class. |
| 322 | >>> class Tree: |
| 323 | ... |
| 324 | ... def __init__(self, label, left=None, right=None): |
| 325 | ... self.label = label |
| 326 | ... self.left = left |
| 327 | ... self.right = right |
| 328 | ... |
| 329 | ... def __repr__(self, level=0, indent=" "): |
Walter Dörwald | 70a6b49 | 2004-02-12 17:35:32 +0000 | [diff] [blame] | 330 | ... s = level*indent + repr(self.label) |
Tim Peters | 6ba5f79 | 2001-06-23 20:45:43 +0000 | [diff] [blame] | 331 | ... if self.left: |
| 332 | ... s = s + "\\n" + self.left.__repr__(level+1, indent) |
| 333 | ... if self.right: |
| 334 | ... s = s + "\\n" + self.right.__repr__(level+1, indent) |
| 335 | ... return s |
| 336 | ... |
| 337 | ... def __iter__(self): |
| 338 | ... return inorder(self) |
| 339 | |
| 340 | >>> # Create a Tree from a list. |
| 341 | >>> def tree(list): |
| 342 | ... n = len(list) |
| 343 | ... if n == 0: |
| 344 | ... return [] |
Tim Peters | 3caca23 | 2001-12-06 06:23:26 +0000 | [diff] [blame] | 345 | ... i = n // 2 |
Tim Peters | 6ba5f79 | 2001-06-23 20:45:43 +0000 | [diff] [blame] | 346 | ... return Tree(list[i], tree(list[:i]), tree(list[i+1:])) |
| 347 | |
| 348 | >>> # Show it off: create a tree. |
| 349 | >>> t = tree("ABCDEFGHIJKLMNOPQRSTUVWXYZ") |
| 350 | |
Tim Peters | d674e17 | 2002-03-10 07:59:13 +0000 | [diff] [blame] | 351 | >>> # A recursive generator that generates Tree labels in in-order. |
Tim Peters | 6ba5f79 | 2001-06-23 20:45:43 +0000 | [diff] [blame] | 352 | >>> def inorder(t): |
| 353 | ... if t: |
| 354 | ... for x in inorder(t.left): |
| 355 | ... yield x |
| 356 | ... yield t.label |
| 357 | ... for x in inorder(t.right): |
| 358 | ... yield x |
| 359 | |
| 360 | >>> # Show it off: create a tree. |
Edward Loper | 103d26e | 2004-08-09 02:03:30 +0000 | [diff] [blame] | 361 | >>> t = tree("ABCDEFGHIJKLMNOPQRSTUVWXYZ") |
| 362 | >>> # Print the nodes of the tree in in-order. |
| 363 | >>> for x in t: |
Guido van Rossum | c420b2f | 2007-02-09 22:09:01 +0000 | [diff] [blame] | 364 | ... print(' '+x, end='') |
| 365 | A B C D E F G H I J K L M N O P Q R S T U V W X Y Z |
Tim Peters | 6ba5f79 | 2001-06-23 20:45:43 +0000 | [diff] [blame] | 366 | |
| 367 | >>> # A non-recursive generator. |
| 368 | >>> def inorder(node): |
| 369 | ... stack = [] |
| 370 | ... while node: |
| 371 | ... while node.left: |
| 372 | ... stack.append(node) |
| 373 | ... node = node.left |
| 374 | ... yield node.label |
| 375 | ... while not node.right: |
| 376 | ... try: |
| 377 | ... node = stack.pop() |
| 378 | ... except IndexError: |
| 379 | ... return |
| 380 | ... yield node.label |
| 381 | ... node = node.right |
| 382 | |
| 383 | >>> # Exercise the non-recursive generator. |
| 384 | >>> for x in t: |
Guido van Rossum | c420b2f | 2007-02-09 22:09:01 +0000 | [diff] [blame] | 385 | ... print(' '+x, end='') |
| 386 | A B C D E F G H I J K L M N O P Q R S T U V W X Y Z |
Tim Peters | 6ba5f79 | 2001-06-23 20:45:43 +0000 | [diff] [blame] | 387 | |
| 388 | """ |
| 389 | |
Tim Peters | b2bc6a9 | 2001-06-24 10:14:27 +0000 | [diff] [blame] | 390 | # Examples from Iterator-List and Python-Dev and c.l.py. |
Tim Peters | 6ba5f79 | 2001-06-23 20:45:43 +0000 | [diff] [blame] | 391 | |
| 392 | email_tests = """ |
| 393 | |
| 394 | The difference between yielding None and returning it. |
| 395 | |
| 396 | >>> def g(): |
| 397 | ... for i in range(3): |
| 398 | ... yield None |
| 399 | ... yield None |
| 400 | ... return |
| 401 | >>> list(g()) |
| 402 | [None, None, None, None] |
| 403 | |
| 404 | Ensure that explicitly raising StopIteration acts like any other exception |
| 405 | in try/except, not like a return. |
| 406 | |
| 407 | >>> def g(): |
| 408 | ... yield 1 |
| 409 | ... try: |
| 410 | ... raise StopIteration |
| 411 | ... except: |
| 412 | ... yield 2 |
| 413 | ... yield 3 |
| 414 | >>> list(g()) |
| 415 | [1, 2, 3] |
Tim Peters | b9e9ff1 | 2001-06-24 03:44:52 +0000 | [diff] [blame] | 416 | |
Tim Peters | b2bc6a9 | 2001-06-24 10:14:27 +0000 | [diff] [blame] | 417 | Next one was posted to c.l.py. |
| 418 | |
| 419 | >>> def gcomb(x, k): |
| 420 | ... "Generate all combinations of k elements from list x." |
| 421 | ... |
| 422 | ... if k > len(x): |
| 423 | ... return |
| 424 | ... if k == 0: |
| 425 | ... yield [] |
| 426 | ... else: |
| 427 | ... first, rest = x[0], x[1:] |
| 428 | ... # A combination does or doesn't contain first. |
| 429 | ... # If it does, the remainder is a k-1 comb of rest. |
| 430 | ... for c in gcomb(rest, k-1): |
| 431 | ... c.insert(0, first) |
| 432 | ... yield c |
| 433 | ... # If it doesn't contain first, it's a k comb of rest. |
| 434 | ... for c in gcomb(rest, k): |
| 435 | ... yield c |
| 436 | |
Guido van Rossum | 805365e | 2007-05-07 22:24:25 +0000 | [diff] [blame] | 437 | >>> seq = list(range(1, 5)) |
Tim Peters | b2bc6a9 | 2001-06-24 10:14:27 +0000 | [diff] [blame] | 438 | >>> for k in range(len(seq) + 2): |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 439 | ... print("%d-combs of %s:" % (k, seq)) |
Tim Peters | b2bc6a9 | 2001-06-24 10:14:27 +0000 | [diff] [blame] | 440 | ... for c in gcomb(seq, k): |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 441 | ... print(" ", c) |
Tim Peters | b2bc6a9 | 2001-06-24 10:14:27 +0000 | [diff] [blame] | 442 | 0-combs of [1, 2, 3, 4]: |
| 443 | [] |
| 444 | 1-combs of [1, 2, 3, 4]: |
| 445 | [1] |
| 446 | [2] |
| 447 | [3] |
| 448 | [4] |
| 449 | 2-combs of [1, 2, 3, 4]: |
| 450 | [1, 2] |
| 451 | [1, 3] |
| 452 | [1, 4] |
| 453 | [2, 3] |
| 454 | [2, 4] |
| 455 | [3, 4] |
| 456 | 3-combs of [1, 2, 3, 4]: |
| 457 | [1, 2, 3] |
| 458 | [1, 2, 4] |
| 459 | [1, 3, 4] |
| 460 | [2, 3, 4] |
| 461 | 4-combs of [1, 2, 3, 4]: |
| 462 | [1, 2, 3, 4] |
| 463 | 5-combs of [1, 2, 3, 4]: |
Tim Peters | 3e7b1a0 | 2001-06-25 19:46:25 +0000 | [diff] [blame] | 464 | |
Tim Peters | e77f2e2 | 2001-06-26 22:24:51 +0000 | [diff] [blame] | 465 | From the Iterators list, about the types of these things. |
Tim Peters | 3e7b1a0 | 2001-06-25 19:46:25 +0000 | [diff] [blame] | 466 | |
| 467 | >>> def g(): |
| 468 | ... yield 1 |
| 469 | ... |
| 470 | >>> type(g) |
Martin v. Löwis | 250ad61 | 2008-04-07 05:43:42 +0000 | [diff] [blame] | 471 | <class 'function'> |
Tim Peters | 3e7b1a0 | 2001-06-25 19:46:25 +0000 | [diff] [blame] | 472 | >>> i = g() |
| 473 | >>> type(i) |
Martin v. Löwis | 250ad61 | 2008-04-07 05:43:42 +0000 | [diff] [blame] | 474 | <class 'generator'> |
Tim Peters | 5d2b77c | 2001-09-03 05:47:38 +0000 | [diff] [blame] | 475 | >>> [s for s in dir(i) if not s.startswith('_')] |
Christian Heimes | af98da1 | 2008-01-27 15:18:18 +0000 | [diff] [blame] | 476 | ['close', 'gi_code', 'gi_frame', 'gi_running', 'send', 'throw'] |
Serhiy Storchaka | 9a11f17 | 2013-01-31 16:11:04 +0200 | [diff] [blame] | 477 | >>> from test.support import HAVE_DOCSTRINGS |
Larry Hastings | 581ee36 | 2014-01-28 05:00:08 -0800 | [diff] [blame] | 478 | >>> print(i.__next__.__doc__ if HAVE_DOCSTRINGS else 'Implement next(self).') |
| 479 | Implement next(self). |
Tim Peters | 3e7b1a0 | 2001-06-25 19:46:25 +0000 | [diff] [blame] | 480 | >>> iter(i) is i |
Guido van Rossum | 77f6a65 | 2002-04-03 22:41:51 +0000 | [diff] [blame] | 481 | True |
Tim Peters | 3e7b1a0 | 2001-06-25 19:46:25 +0000 | [diff] [blame] | 482 | >>> import types |
| 483 | >>> isinstance(i, types.GeneratorType) |
Guido van Rossum | 77f6a65 | 2002-04-03 22:41:51 +0000 | [diff] [blame] | 484 | True |
Tim Peters | e77f2e2 | 2001-06-26 22:24:51 +0000 | [diff] [blame] | 485 | |
| 486 | And more, added later. |
| 487 | |
| 488 | >>> i.gi_running |
| 489 | 0 |
| 490 | >>> type(i.gi_frame) |
Martin v. Löwis | 250ad61 | 2008-04-07 05:43:42 +0000 | [diff] [blame] | 491 | <class 'frame'> |
Tim Peters | e77f2e2 | 2001-06-26 22:24:51 +0000 | [diff] [blame] | 492 | >>> i.gi_running = 42 |
| 493 | Traceback (most recent call last): |
| 494 | ... |
Collin Winter | 42dae6a | 2007-03-28 21:44:53 +0000 | [diff] [blame] | 495 | AttributeError: readonly attribute |
Tim Peters | e77f2e2 | 2001-06-26 22:24:51 +0000 | [diff] [blame] | 496 | >>> def g(): |
| 497 | ... yield me.gi_running |
| 498 | >>> me = g() |
| 499 | >>> me.gi_running |
| 500 | 0 |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 501 | >>> next(me) |
Tim Peters | e77f2e2 | 2001-06-26 22:24:51 +0000 | [diff] [blame] | 502 | 1 |
| 503 | >>> me.gi_running |
| 504 | 0 |
Tim Peters | 3530266 | 2001-07-02 01:38:33 +0000 | [diff] [blame] | 505 | |
| 506 | A clever union-find implementation from c.l.py, due to David Eppstein. |
| 507 | Sent: Friday, June 29, 2001 12:16 PM |
| 508 | To: python-list@python.org |
| 509 | Subject: Re: PEP 255: Simple Generators |
| 510 | |
| 511 | >>> class disjointSet: |
| 512 | ... def __init__(self, name): |
| 513 | ... self.name = name |
| 514 | ... self.parent = None |
| 515 | ... self.generator = self.generate() |
| 516 | ... |
| 517 | ... def generate(self): |
| 518 | ... while not self.parent: |
| 519 | ... yield self |
| 520 | ... for x in self.parent.generator: |
| 521 | ... yield x |
| 522 | ... |
| 523 | ... def find(self): |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 524 | ... return next(self.generator) |
Tim Peters | 3530266 | 2001-07-02 01:38:33 +0000 | [diff] [blame] | 525 | ... |
| 526 | ... def union(self, parent): |
| 527 | ... if self.parent: |
| 528 | ... raise ValueError("Sorry, I'm not a root!") |
| 529 | ... self.parent = parent |
| 530 | ... |
| 531 | ... def __str__(self): |
| 532 | ... return self.name |
Tim Peters | 3530266 | 2001-07-02 01:38:33 +0000 | [diff] [blame] | 533 | |
| 534 | >>> names = "ABCDEFGHIJKLM" |
| 535 | >>> sets = [disjointSet(name) for name in names] |
| 536 | >>> roots = sets[:] |
| 537 | |
| 538 | >>> import random |
Raymond Hettinger | 28de64f | 2008-01-13 23:40:30 +0000 | [diff] [blame] | 539 | >>> gen = random.Random(42) |
Tim Peters | 3530266 | 2001-07-02 01:38:33 +0000 | [diff] [blame] | 540 | >>> while 1: |
| 541 | ... for s in sets: |
Guido van Rossum | c420b2f | 2007-02-09 22:09:01 +0000 | [diff] [blame] | 542 | ... print(" %s->%s" % (s, s.find()), end='') |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 543 | ... print() |
Tim Peters | 3530266 | 2001-07-02 01:38:33 +0000 | [diff] [blame] | 544 | ... if len(roots) > 1: |
Raymond Hettinger | dd24a9f | 2002-12-30 00:46:09 +0000 | [diff] [blame] | 545 | ... s1 = gen.choice(roots) |
Tim Peters | 3530266 | 2001-07-02 01:38:33 +0000 | [diff] [blame] | 546 | ... roots.remove(s1) |
Raymond Hettinger | dd24a9f | 2002-12-30 00:46:09 +0000 | [diff] [blame] | 547 | ... s2 = gen.choice(roots) |
Tim Peters | 3530266 | 2001-07-02 01:38:33 +0000 | [diff] [blame] | 548 | ... s1.union(s2) |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 549 | ... print("merged", s1, "into", s2) |
Tim Peters | 3530266 | 2001-07-02 01:38:33 +0000 | [diff] [blame] | 550 | ... else: |
| 551 | ... break |
Guido van Rossum | c420b2f | 2007-02-09 22:09:01 +0000 | [diff] [blame] | 552 | A->A B->B C->C D->D E->E F->F G->G H->H I->I J->J K->K L->L M->M |
Raymond Hettinger | c585eec | 2010-09-07 15:00:15 +0000 | [diff] [blame] | 553 | merged K into B |
| 554 | A->A B->B C->C D->D E->E F->F G->G H->H I->I J->J K->B L->L M->M |
Raymond Hettinger | 28de64f | 2008-01-13 23:40:30 +0000 | [diff] [blame] | 555 | merged A into F |
Raymond Hettinger | c585eec | 2010-09-07 15:00:15 +0000 | [diff] [blame] | 556 | A->F B->B C->C D->D E->E F->F G->G H->H I->I J->J K->B L->L M->M |
| 557 | merged E into F |
| 558 | A->F B->B C->C D->D E->F F->F G->G H->H I->I J->J K->B L->L M->M |
| 559 | merged D into C |
| 560 | A->F B->B C->C D->C E->F F->F G->G H->H I->I J->J K->B L->L M->M |
Raymond Hettinger | 28de64f | 2008-01-13 23:40:30 +0000 | [diff] [blame] | 561 | merged M into C |
Raymond Hettinger | c585eec | 2010-09-07 15:00:15 +0000 | [diff] [blame] | 562 | A->F B->B C->C D->C E->F F->F G->G H->H I->I J->J K->B L->L M->C |
| 563 | merged J into B |
| 564 | A->F B->B C->C D->C E->F F->F G->G H->H I->I J->B K->B L->L M->C |
| 565 | merged B into C |
| 566 | A->F B->C C->C D->C E->F F->F G->G H->H I->I J->C K->C L->L M->C |
| 567 | merged F into G |
| 568 | A->G B->C C->C D->C E->G F->G G->G H->H I->I J->C K->C L->L M->C |
| 569 | merged L into C |
| 570 | A->G B->C C->C D->C E->G F->G G->G H->H I->I J->C K->C L->C M->C |
| 571 | merged G into I |
| 572 | A->I B->C C->C D->C E->I F->I G->I H->H I->I J->C K->C L->C M->C |
| 573 | merged I into H |
| 574 | A->H B->C C->C D->C E->H F->H G->H H->H I->H J->C K->C L->C M->C |
| 575 | merged C into H |
| 576 | A->H B->H C->H D->H E->H F->H G->H H->H I->H J->H K->H L->H M->H |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 577 | |
Tim Peters | 6ba5f79 | 2001-06-23 20:45:43 +0000 | [diff] [blame] | 578 | """ |
Barry Warsaw | 04f357c | 2002-07-23 19:04:11 +0000 | [diff] [blame] | 579 | # Emacs turd ' |
Tim Peters | 6ba5f79 | 2001-06-23 20:45:43 +0000 | [diff] [blame] | 580 | |
Tim Peters | 0f9da0a | 2001-06-23 21:01:47 +0000 | [diff] [blame] | 581 | # Fun tests (for sufficiently warped notions of "fun"). |
| 582 | |
| 583 | fun_tests = """ |
| 584 | |
| 585 | Build up to a recursive Sieve of Eratosthenes generator. |
| 586 | |
| 587 | >>> def firstn(g, n): |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 588 | ... return [next(g) for i in range(n)] |
Tim Peters | 0f9da0a | 2001-06-23 21:01:47 +0000 | [diff] [blame] | 589 | |
| 590 | >>> def intsfrom(i): |
| 591 | ... while 1: |
| 592 | ... yield i |
| 593 | ... i += 1 |
| 594 | |
| 595 | >>> firstn(intsfrom(5), 7) |
| 596 | [5, 6, 7, 8, 9, 10, 11] |
| 597 | |
| 598 | >>> def exclude_multiples(n, ints): |
| 599 | ... for i in ints: |
| 600 | ... if i % n: |
| 601 | ... yield i |
| 602 | |
| 603 | >>> firstn(exclude_multiples(3, intsfrom(1)), 6) |
| 604 | [1, 2, 4, 5, 7, 8] |
| 605 | |
| 606 | >>> def sieve(ints): |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 607 | ... prime = next(ints) |
Tim Peters | 0f9da0a | 2001-06-23 21:01:47 +0000 | [diff] [blame] | 608 | ... yield prime |
| 609 | ... not_divisible_by_prime = exclude_multiples(prime, ints) |
| 610 | ... for p in sieve(not_divisible_by_prime): |
| 611 | ... yield p |
| 612 | |
| 613 | >>> primes = sieve(intsfrom(2)) |
| 614 | >>> firstn(primes, 20) |
| 615 | [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71] |
Tim Peters | b9e9ff1 | 2001-06-24 03:44:52 +0000 | [diff] [blame] | 616 | |
Tim Peters | f6ed074 | 2001-06-27 07:17:57 +0000 | [diff] [blame] | 617 | |
Tim Peters | b9e9ff1 | 2001-06-24 03:44:52 +0000 | [diff] [blame] | 618 | Another famous problem: generate all integers of the form |
| 619 | 2**i * 3**j * 5**k |
| 620 | in increasing order, where i,j,k >= 0. Trickier than it may look at first! |
| 621 | Try writing it without generators, and correctly, and without generating |
| 622 | 3 internal results for each result output. |
| 623 | |
| 624 | >>> def times(n, g): |
| 625 | ... for i in g: |
| 626 | ... yield n * i |
| 627 | >>> firstn(times(10, intsfrom(1)), 10) |
| 628 | [10, 20, 30, 40, 50, 60, 70, 80, 90, 100] |
| 629 | |
| 630 | >>> def merge(g, h): |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 631 | ... ng = next(g) |
| 632 | ... nh = next(h) |
Tim Peters | b9e9ff1 | 2001-06-24 03:44:52 +0000 | [diff] [blame] | 633 | ... while 1: |
| 634 | ... if ng < nh: |
| 635 | ... yield ng |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 636 | ... ng = next(g) |
Tim Peters | b9e9ff1 | 2001-06-24 03:44:52 +0000 | [diff] [blame] | 637 | ... elif ng > nh: |
| 638 | ... yield nh |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 639 | ... nh = next(h) |
Tim Peters | b9e9ff1 | 2001-06-24 03:44:52 +0000 | [diff] [blame] | 640 | ... else: |
| 641 | ... yield ng |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 642 | ... ng = next(g) |
| 643 | ... nh = next(h) |
Tim Peters | b9e9ff1 | 2001-06-24 03:44:52 +0000 | [diff] [blame] | 644 | |
Tim Peters | f6ed074 | 2001-06-27 07:17:57 +0000 | [diff] [blame] | 645 | The following works, but is doing a whale of a lot of redundant work -- |
| 646 | it's not clear how to get the internal uses of m235 to share a single |
| 647 | generator. Note that me_times2 (etc) each need to see every element in the |
| 648 | result sequence. So this is an example where lazy lists are more natural |
| 649 | (you can look at the head of a lazy list any number of times). |
Tim Peters | b9e9ff1 | 2001-06-24 03:44:52 +0000 | [diff] [blame] | 650 | |
| 651 | >>> def m235(): |
| 652 | ... yield 1 |
| 653 | ... me_times2 = times(2, m235()) |
| 654 | ... me_times3 = times(3, m235()) |
| 655 | ... me_times5 = times(5, m235()) |
| 656 | ... for i in merge(merge(me_times2, |
| 657 | ... me_times3), |
| 658 | ... me_times5): |
| 659 | ... yield i |
| 660 | |
Tim Peters | f6ed074 | 2001-06-27 07:17:57 +0000 | [diff] [blame] | 661 | Don't print "too many" of these -- the implementation above is extremely |
| 662 | inefficient: each call of m235() leads to 3 recursive calls, and in |
| 663 | turn each of those 3 more, and so on, and so on, until we've descended |
| 664 | enough levels to satisfy the print stmts. Very odd: when I printed 5 |
| 665 | lines of results below, this managed to screw up Win98's malloc in "the |
| 666 | usual" way, i.e. the heap grew over 4Mb so Win98 started fragmenting |
| 667 | address space, and it *looked* like a very slow leak. |
| 668 | |
Tim Peters | b9e9ff1 | 2001-06-24 03:44:52 +0000 | [diff] [blame] | 669 | >>> result = m235() |
Tim Peters | f6ed074 | 2001-06-27 07:17:57 +0000 | [diff] [blame] | 670 | >>> for i in range(3): |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 671 | ... print(firstn(result, 15)) |
Tim Peters | b9e9ff1 | 2001-06-24 03:44:52 +0000 | [diff] [blame] | 672 | [1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 16, 18, 20, 24] |
| 673 | [25, 27, 30, 32, 36, 40, 45, 48, 50, 54, 60, 64, 72, 75, 80] |
| 674 | [81, 90, 96, 100, 108, 120, 125, 128, 135, 144, 150, 160, 162, 180, 192] |
Tim Peters | ee30927 | 2001-06-24 05:47:06 +0000 | [diff] [blame] | 675 | |
| 676 | Heh. Here's one way to get a shared list, complete with an excruciating |
| 677 | namespace renaming trick. The *pretty* part is that the times() and merge() |
| 678 | functions can be reused as-is, because they only assume their stream |
| 679 | arguments are iterable -- a LazyList is the same as a generator to times(). |
| 680 | |
| 681 | >>> class LazyList: |
| 682 | ... def __init__(self, g): |
| 683 | ... self.sofar = [] |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 684 | ... self.fetch = g.__next__ |
Tim Peters | ee30927 | 2001-06-24 05:47:06 +0000 | [diff] [blame] | 685 | ... |
| 686 | ... def __getitem__(self, i): |
| 687 | ... sofar, fetch = self.sofar, self.fetch |
| 688 | ... while i >= len(sofar): |
| 689 | ... sofar.append(fetch()) |
| 690 | ... return sofar[i] |
| 691 | |
| 692 | >>> def m235(): |
| 693 | ... yield 1 |
Tim Peters | ea2e97a | 2001-06-24 07:10:02 +0000 | [diff] [blame] | 694 | ... # Gack: m235 below actually refers to a LazyList. |
Tim Peters | ee30927 | 2001-06-24 05:47:06 +0000 | [diff] [blame] | 695 | ... me_times2 = times(2, m235) |
| 696 | ... me_times3 = times(3, m235) |
| 697 | ... me_times5 = times(5, m235) |
| 698 | ... for i in merge(merge(me_times2, |
| 699 | ... me_times3), |
| 700 | ... me_times5): |
| 701 | ... yield i |
| 702 | |
Tim Peters | f6ed074 | 2001-06-27 07:17:57 +0000 | [diff] [blame] | 703 | Print as many of these as you like -- *this* implementation is memory- |
Neil Schemenauer | b20e9db | 2001-07-12 13:26:41 +0000 | [diff] [blame] | 704 | efficient. |
Tim Peters | f6ed074 | 2001-06-27 07:17:57 +0000 | [diff] [blame] | 705 | |
Tim Peters | ee30927 | 2001-06-24 05:47:06 +0000 | [diff] [blame] | 706 | >>> m235 = LazyList(m235()) |
| 707 | >>> for i in range(5): |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 708 | ... print([m235[j] for j in range(15*i, 15*(i+1))]) |
Tim Peters | ee30927 | 2001-06-24 05:47:06 +0000 | [diff] [blame] | 709 | [1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 16, 18, 20, 24] |
| 710 | [25, 27, 30, 32, 36, 40, 45, 48, 50, 54, 60, 64, 72, 75, 80] |
| 711 | [81, 90, 96, 100, 108, 120, 125, 128, 135, 144, 150, 160, 162, 180, 192] |
| 712 | [200, 216, 225, 240, 243, 250, 256, 270, 288, 300, 320, 324, 360, 375, 384] |
| 713 | [400, 405, 432, 450, 480, 486, 500, 512, 540, 576, 600, 625, 640, 648, 675] |
Tim Peters | f6ed074 | 2001-06-27 07:17:57 +0000 | [diff] [blame] | 714 | |
Tim Peters | f6ed074 | 2001-06-27 07:17:57 +0000 | [diff] [blame] | 715 | Ye olde Fibonacci generator, LazyList style. |
| 716 | |
| 717 | >>> def fibgen(a, b): |
| 718 | ... |
| 719 | ... def sum(g, h): |
| 720 | ... while 1: |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 721 | ... yield next(g) + next(h) |
Tim Peters | f6ed074 | 2001-06-27 07:17:57 +0000 | [diff] [blame] | 722 | ... |
| 723 | ... def tail(g): |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 724 | ... next(g) # throw first away |
Tim Peters | f6ed074 | 2001-06-27 07:17:57 +0000 | [diff] [blame] | 725 | ... for x in g: |
| 726 | ... yield x |
| 727 | ... |
| 728 | ... yield a |
| 729 | ... yield b |
| 730 | ... for s in sum(iter(fib), |
| 731 | ... tail(iter(fib))): |
| 732 | ... yield s |
| 733 | |
| 734 | >>> fib = LazyList(fibgen(1, 2)) |
| 735 | >>> firstn(iter(fib), 17) |
| 736 | [1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584] |
Georg Brandl | 52715f6 | 2005-08-24 09:02:29 +0000 | [diff] [blame] | 737 | |
| 738 | |
| 739 | Running after your tail with itertools.tee (new in version 2.4) |
| 740 | |
| 741 | The algorithms "m235" (Hamming) and Fibonacci presented above are both |
| 742 | examples of a whole family of FP (functional programming) algorithms |
| 743 | where a function produces and returns a list while the production algorithm |
| 744 | suppose the list as already produced by recursively calling itself. |
| 745 | For these algorithms to work, they must: |
| 746 | |
| 747 | - produce at least a first element without presupposing the existence of |
| 748 | the rest of the list |
| 749 | - produce their elements in a lazy manner |
| 750 | |
| 751 | To work efficiently, the beginning of the list must not be recomputed over |
| 752 | and over again. This is ensured in most FP languages as a built-in feature. |
| 753 | In python, we have to explicitly maintain a list of already computed results |
| 754 | and abandon genuine recursivity. |
| 755 | |
| 756 | This is what had been attempted above with the LazyList class. One problem |
| 757 | with that class is that it keeps a list of all of the generated results and |
| 758 | therefore continually grows. This partially defeats the goal of the generator |
| 759 | concept, viz. produce the results only as needed instead of producing them |
| 760 | all and thereby wasting memory. |
| 761 | |
| 762 | Thanks to itertools.tee, it is now clear "how to get the internal uses of |
| 763 | m235 to share a single generator". |
| 764 | |
| 765 | >>> from itertools import tee |
| 766 | >>> def m235(): |
| 767 | ... def _m235(): |
| 768 | ... yield 1 |
| 769 | ... for n in merge(times(2, m2), |
| 770 | ... merge(times(3, m3), |
| 771 | ... times(5, m5))): |
| 772 | ... yield n |
Thomas Wouters | 49fd7fa | 2006-04-21 10:40:58 +0000 | [diff] [blame] | 773 | ... m1 = _m235() |
| 774 | ... m2, m3, m5, mRes = tee(m1, 4) |
Georg Brandl | 52715f6 | 2005-08-24 09:02:29 +0000 | [diff] [blame] | 775 | ... return mRes |
| 776 | |
| 777 | >>> it = m235() |
| 778 | >>> for i in range(5): |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 779 | ... print(firstn(it, 15)) |
Georg Brandl | 52715f6 | 2005-08-24 09:02:29 +0000 | [diff] [blame] | 780 | [1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 16, 18, 20, 24] |
| 781 | [25, 27, 30, 32, 36, 40, 45, 48, 50, 54, 60, 64, 72, 75, 80] |
| 782 | [81, 90, 96, 100, 108, 120, 125, 128, 135, 144, 150, 160, 162, 180, 192] |
| 783 | [200, 216, 225, 240, 243, 250, 256, 270, 288, 300, 320, 324, 360, 375, 384] |
| 784 | [400, 405, 432, 450, 480, 486, 500, 512, 540, 576, 600, 625, 640, 648, 675] |
| 785 | |
| 786 | The "tee" function does just what we want. It internally keeps a generated |
| 787 | result for as long as it has not been "consumed" from all of the duplicated |
| 788 | iterators, whereupon it is deleted. You can therefore print the hamming |
| 789 | sequence during hours without increasing memory usage, or very little. |
| 790 | |
Thomas Wouters | 49fd7fa | 2006-04-21 10:40:58 +0000 | [diff] [blame] | 791 | The beauty of it is that recursive running-after-their-tail FP algorithms |
Georg Brandl | 52715f6 | 2005-08-24 09:02:29 +0000 | [diff] [blame] | 792 | are quite straightforwardly expressed with this Python idiom. |
| 793 | |
Georg Brandl | 52715f6 | 2005-08-24 09:02:29 +0000 | [diff] [blame] | 794 | Ye olde Fibonacci generator, tee style. |
| 795 | |
| 796 | >>> def fib(): |
Tim Peters | 9e34c04 | 2005-08-26 15:20:46 +0000 | [diff] [blame] | 797 | ... |
Georg Brandl | 52715f6 | 2005-08-24 09:02:29 +0000 | [diff] [blame] | 798 | ... def _isum(g, h): |
| 799 | ... while 1: |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 800 | ... yield next(g) + next(h) |
Tim Peters | 9e34c04 | 2005-08-26 15:20:46 +0000 | [diff] [blame] | 801 | ... |
Georg Brandl | 52715f6 | 2005-08-24 09:02:29 +0000 | [diff] [blame] | 802 | ... def _fib(): |
| 803 | ... yield 1 |
| 804 | ... yield 2 |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 805 | ... next(fibTail) # throw first away |
Georg Brandl | 52715f6 | 2005-08-24 09:02:29 +0000 | [diff] [blame] | 806 | ... for res in _isum(fibHead, fibTail): |
| 807 | ... yield res |
Tim Peters | 9e34c04 | 2005-08-26 15:20:46 +0000 | [diff] [blame] | 808 | ... |
Thomas Wouters | 49fd7fa | 2006-04-21 10:40:58 +0000 | [diff] [blame] | 809 | ... realfib = _fib() |
| 810 | ... fibHead, fibTail, fibRes = tee(realfib, 3) |
Georg Brandl | 52715f6 | 2005-08-24 09:02:29 +0000 | [diff] [blame] | 811 | ... return fibRes |
| 812 | |
| 813 | >>> firstn(fib(), 17) |
| 814 | [1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584] |
| 815 | |
Tim Peters | 0f9da0a | 2001-06-23 21:01:47 +0000 | [diff] [blame] | 816 | """ |
| 817 | |
Tim Peters | b6c3cea | 2001-06-26 03:36:28 +0000 | [diff] [blame] | 818 | # syntax_tests mostly provokes SyntaxErrors. Also fiddling with #if 0 |
| 819 | # hackery. |
Tim Peters | ee30927 | 2001-06-24 05:47:06 +0000 | [diff] [blame] | 820 | |
Tim Peters | ea2e97a | 2001-06-24 07:10:02 +0000 | [diff] [blame] | 821 | syntax_tests = """ |
| 822 | |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 823 | These are fine: |
Tim Peters | ea2e97a | 2001-06-24 07:10:02 +0000 | [diff] [blame] | 824 | |
| 825 | >>> def f(): |
| 826 | ... yield 1 |
| 827 | ... return |
| 828 | |
Tim Peters | aef8cfa | 2004-08-27 15:12:49 +0000 | [diff] [blame] | 829 | >>> def f(): |
Tim Peters | ea2e97a | 2001-06-24 07:10:02 +0000 | [diff] [blame] | 830 | ... try: |
| 831 | ... yield 1 |
| 832 | ... finally: |
| 833 | ... pass |
Tim Peters | ea2e97a | 2001-06-24 07:10:02 +0000 | [diff] [blame] | 834 | |
Tim Peters | aef8cfa | 2004-08-27 15:12:49 +0000 | [diff] [blame] | 835 | >>> def f(): |
Tim Peters | ea2e97a | 2001-06-24 07:10:02 +0000 | [diff] [blame] | 836 | ... try: |
| 837 | ... try: |
Tim Peters | 3caca23 | 2001-12-06 06:23:26 +0000 | [diff] [blame] | 838 | ... 1//0 |
Tim Peters | ea2e97a | 2001-06-24 07:10:02 +0000 | [diff] [blame] | 839 | ... except ZeroDivisionError: |
Tim Peters | 536cf99 | 2005-12-25 23:18:31 +0000 | [diff] [blame] | 840 | ... yield 666 |
Tim Peters | ea2e97a | 2001-06-24 07:10:02 +0000 | [diff] [blame] | 841 | ... except: |
| 842 | ... pass |
| 843 | ... finally: |
| 844 | ... pass |
Tim Peters | ea2e97a | 2001-06-24 07:10:02 +0000 | [diff] [blame] | 845 | |
| 846 | >>> def f(): |
| 847 | ... try: |
| 848 | ... try: |
| 849 | ... yield 12 |
Tim Peters | 3caca23 | 2001-12-06 06:23:26 +0000 | [diff] [blame] | 850 | ... 1//0 |
Tim Peters | ea2e97a | 2001-06-24 07:10:02 +0000 | [diff] [blame] | 851 | ... except ZeroDivisionError: |
| 852 | ... yield 666 |
| 853 | ... except: |
| 854 | ... try: |
| 855 | ... x = 12 |
| 856 | ... finally: |
| 857 | ... yield 12 |
| 858 | ... except: |
| 859 | ... return |
| 860 | >>> list(f()) |
| 861 | [12, 666] |
Tim Peters | b6c3cea | 2001-06-26 03:36:28 +0000 | [diff] [blame] | 862 | |
| 863 | >>> def f(): |
Tim Peters | 08a898f | 2001-06-28 01:52:22 +0000 | [diff] [blame] | 864 | ... yield |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 865 | >>> type(f()) |
Martin v. Löwis | 250ad61 | 2008-04-07 05:43:42 +0000 | [diff] [blame] | 866 | <class 'generator'> |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 867 | |
Tim Peters | 08a898f | 2001-06-28 01:52:22 +0000 | [diff] [blame] | 868 | |
| 869 | >>> def f(): |
| 870 | ... if 0: |
| 871 | ... yield |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 872 | >>> type(f()) |
Martin v. Löwis | 250ad61 | 2008-04-07 05:43:42 +0000 | [diff] [blame] | 873 | <class 'generator'> |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 874 | |
Tim Peters | 08a898f | 2001-06-28 01:52:22 +0000 | [diff] [blame] | 875 | |
| 876 | >>> def f(): |
Tim Peters | b6c3cea | 2001-06-26 03:36:28 +0000 | [diff] [blame] | 877 | ... if 0: |
| 878 | ... yield 1 |
| 879 | >>> type(f()) |
Martin v. Löwis | 250ad61 | 2008-04-07 05:43:42 +0000 | [diff] [blame] | 880 | <class 'generator'> |
Tim Peters | b6c3cea | 2001-06-26 03:36:28 +0000 | [diff] [blame] | 881 | |
| 882 | >>> def f(): |
| 883 | ... if "": |
| 884 | ... yield None |
| 885 | >>> type(f()) |
Martin v. Löwis | 250ad61 | 2008-04-07 05:43:42 +0000 | [diff] [blame] | 886 | <class 'generator'> |
Tim Peters | b6c3cea | 2001-06-26 03:36:28 +0000 | [diff] [blame] | 887 | |
| 888 | >>> def f(): |
| 889 | ... return |
| 890 | ... try: |
| 891 | ... if x==4: |
| 892 | ... pass |
| 893 | ... elif 0: |
| 894 | ... try: |
Tim Peters | 3caca23 | 2001-12-06 06:23:26 +0000 | [diff] [blame] | 895 | ... 1//0 |
Tim Peters | b6c3cea | 2001-06-26 03:36:28 +0000 | [diff] [blame] | 896 | ... except SyntaxError: |
| 897 | ... pass |
| 898 | ... else: |
| 899 | ... if 0: |
| 900 | ... while 12: |
| 901 | ... x += 1 |
| 902 | ... yield 2 # don't blink |
| 903 | ... f(a, b, c, d, e) |
| 904 | ... else: |
| 905 | ... pass |
| 906 | ... except: |
| 907 | ... x = 1 |
| 908 | ... return |
| 909 | >>> type(f()) |
Martin v. Löwis | 250ad61 | 2008-04-07 05:43:42 +0000 | [diff] [blame] | 910 | <class 'generator'> |
Tim Peters | b6c3cea | 2001-06-26 03:36:28 +0000 | [diff] [blame] | 911 | |
| 912 | >>> def f(): |
| 913 | ... if 0: |
| 914 | ... def g(): |
| 915 | ... yield 1 |
| 916 | ... |
| 917 | >>> type(f()) |
Martin v. Löwis | 250ad61 | 2008-04-07 05:43:42 +0000 | [diff] [blame] | 918 | <class 'NoneType'> |
Tim Peters | b6c3cea | 2001-06-26 03:36:28 +0000 | [diff] [blame] | 919 | |
| 920 | >>> def f(): |
| 921 | ... if 0: |
| 922 | ... class C: |
| 923 | ... def __init__(self): |
| 924 | ... yield 1 |
| 925 | ... def f(self): |
| 926 | ... yield 2 |
| 927 | >>> type(f()) |
Martin v. Löwis | 250ad61 | 2008-04-07 05:43:42 +0000 | [diff] [blame] | 928 | <class 'NoneType'> |
Tim Peters | 08a898f | 2001-06-28 01:52:22 +0000 | [diff] [blame] | 929 | |
| 930 | >>> def f(): |
| 931 | ... if 0: |
| 932 | ... return |
| 933 | ... if 0: |
| 934 | ... yield 2 |
| 935 | >>> type(f()) |
Martin v. Löwis | 250ad61 | 2008-04-07 05:43:42 +0000 | [diff] [blame] | 936 | <class 'generator'> |
Tim Peters | 08a898f | 2001-06-28 01:52:22 +0000 | [diff] [blame] | 937 | |
Guido van Rossum | c5fe5eb | 2002-06-12 03:45:21 +0000 | [diff] [blame] | 938 | This one caused a crash (see SF bug 567538): |
| 939 | |
| 940 | >>> def f(): |
| 941 | ... for i in range(3): |
| 942 | ... try: |
| 943 | ... continue |
| 944 | ... finally: |
| 945 | ... yield i |
Tim Peters | c411dba | 2002-07-16 21:35:23 +0000 | [diff] [blame] | 946 | ... |
Guido van Rossum | c5fe5eb | 2002-06-12 03:45:21 +0000 | [diff] [blame] | 947 | >>> g = f() |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 948 | >>> print(next(g)) |
Guido van Rossum | c5fe5eb | 2002-06-12 03:45:21 +0000 | [diff] [blame] | 949 | 0 |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 950 | >>> print(next(g)) |
Guido van Rossum | c5fe5eb | 2002-06-12 03:45:21 +0000 | [diff] [blame] | 951 | 1 |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 952 | >>> print(next(g)) |
Guido van Rossum | c5fe5eb | 2002-06-12 03:45:21 +0000 | [diff] [blame] | 953 | 2 |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 954 | >>> print(next(g)) |
Guido van Rossum | c5fe5eb | 2002-06-12 03:45:21 +0000 | [diff] [blame] | 955 | Traceback (most recent call last): |
| 956 | StopIteration |
Christian Heimes | af98da1 | 2008-01-27 15:18:18 +0000 | [diff] [blame] | 957 | |
| 958 | |
| 959 | Test the gi_code attribute |
| 960 | |
| 961 | >>> def f(): |
| 962 | ... yield 5 |
| 963 | ... |
| 964 | >>> g = f() |
| 965 | >>> g.gi_code is f.__code__ |
| 966 | True |
| 967 | >>> next(g) |
| 968 | 5 |
| 969 | >>> next(g) |
| 970 | Traceback (most recent call last): |
| 971 | StopIteration |
| 972 | >>> g.gi_code is f.__code__ |
| 973 | True |
| 974 | |
Alexandre Vassalotti | e9f305f | 2008-05-16 04:39:54 +0000 | [diff] [blame] | 975 | |
| 976 | Test the __name__ attribute and the repr() |
| 977 | |
| 978 | >>> def f(): |
| 979 | ... yield 5 |
| 980 | ... |
| 981 | >>> g = f() |
| 982 | >>> g.__name__ |
| 983 | 'f' |
| 984 | >>> repr(g) # doctest: +ELLIPSIS |
Alexandre Vassalotti | bee3253 | 2008-05-16 18:15:12 +0000 | [diff] [blame] | 985 | '<generator object f at ...>' |
Benjamin Peterson | 371ccfb | 2008-12-27 19:03:36 +0000 | [diff] [blame] | 986 | |
| 987 | Lambdas shouldn't have their usual return behavior. |
| 988 | |
| 989 | >>> x = lambda: (yield 1) |
| 990 | >>> list(x()) |
| 991 | [1] |
| 992 | |
| 993 | >>> x = lambda: ((yield 1), (yield 2)) |
| 994 | >>> list(x()) |
| 995 | [1, 2] |
Tim Peters | ea2e97a | 2001-06-24 07:10:02 +0000 | [diff] [blame] | 996 | """ |
| 997 | |
Tim Peters | be4f0a7 | 2001-06-29 02:41:16 +0000 | [diff] [blame] | 998 | # conjoin is a simple backtracking generator, named in honor of Icon's |
| 999 | # "conjunction" control structure. Pass a list of no-argument functions |
| 1000 | # that return iterable objects. Easiest to explain by example: assume the |
| 1001 | # function list [x, y, z] is passed. Then conjoin acts like: |
| 1002 | # |
| 1003 | # def g(): |
| 1004 | # values = [None] * 3 |
| 1005 | # for values[0] in x(): |
| 1006 | # for values[1] in y(): |
| 1007 | # for values[2] in z(): |
| 1008 | # yield values |
| 1009 | # |
| 1010 | # So some 3-lists of values *may* be generated, each time we successfully |
| 1011 | # get into the innermost loop. If an iterator fails (is exhausted) before |
| 1012 | # then, it "backtracks" to get the next value from the nearest enclosing |
| 1013 | # iterator (the one "to the left"), and starts all over again at the next |
| 1014 | # slot (pumps a fresh iterator). Of course this is most useful when the |
| 1015 | # iterators have side-effects, so that which values *can* be generated at |
| 1016 | # each slot depend on the values iterated at previous slots. |
| 1017 | |
Benjamin Peterson | 78565b2 | 2009-06-28 19:19:51 +0000 | [diff] [blame] | 1018 | def simple_conjoin(gs): |
Tim Peters | be4f0a7 | 2001-06-29 02:41:16 +0000 | [diff] [blame] | 1019 | |
| 1020 | values = [None] * len(gs) |
| 1021 | |
Benjamin Peterson | 78565b2 | 2009-06-28 19:19:51 +0000 | [diff] [blame] | 1022 | def gen(i): |
Tim Peters | be4f0a7 | 2001-06-29 02:41:16 +0000 | [diff] [blame] | 1023 | if i >= len(gs): |
| 1024 | yield values |
| 1025 | else: |
| 1026 | for values[i] in gs[i](): |
| 1027 | for x in gen(i+1): |
| 1028 | yield x |
| 1029 | |
| 1030 | for x in gen(0): |
| 1031 | yield x |
| 1032 | |
Tim Peters | c468fd2 | 2001-06-30 07:29:44 +0000 | [diff] [blame] | 1033 | # That works fine, but recursing a level and checking i against len(gs) for |
| 1034 | # each item produced is inefficient. By doing manual loop unrolling across |
| 1035 | # generator boundaries, it's possible to eliminate most of that overhead. |
| 1036 | # This isn't worth the bother *in general* for generators, but conjoin() is |
| 1037 | # a core building block for some CPU-intensive generator applications. |
| 1038 | |
| 1039 | def conjoin(gs): |
| 1040 | |
| 1041 | n = len(gs) |
| 1042 | values = [None] * n |
| 1043 | |
| 1044 | # Do one loop nest at time recursively, until the # of loop nests |
| 1045 | # remaining is divisible by 3. |
| 1046 | |
Benjamin Peterson | 78565b2 | 2009-06-28 19:19:51 +0000 | [diff] [blame] | 1047 | def gen(i): |
Tim Peters | c468fd2 | 2001-06-30 07:29:44 +0000 | [diff] [blame] | 1048 | if i >= n: |
| 1049 | yield values |
| 1050 | |
| 1051 | elif (n-i) % 3: |
| 1052 | ip1 = i+1 |
| 1053 | for values[i] in gs[i](): |
| 1054 | for x in gen(ip1): |
| 1055 | yield x |
| 1056 | |
| 1057 | else: |
| 1058 | for x in _gen3(i): |
| 1059 | yield x |
| 1060 | |
| 1061 | # Do three loop nests at a time, recursing only if at least three more |
| 1062 | # remain. Don't call directly: this is an internal optimization for |
| 1063 | # gen's use. |
| 1064 | |
Benjamin Peterson | 78565b2 | 2009-06-28 19:19:51 +0000 | [diff] [blame] | 1065 | def _gen3(i): |
Tim Peters | c468fd2 | 2001-06-30 07:29:44 +0000 | [diff] [blame] | 1066 | assert i < n and (n-i) % 3 == 0 |
| 1067 | ip1, ip2, ip3 = i+1, i+2, i+3 |
| 1068 | g, g1, g2 = gs[i : ip3] |
| 1069 | |
| 1070 | if ip3 >= n: |
| 1071 | # These are the last three, so we can yield values directly. |
| 1072 | for values[i] in g(): |
| 1073 | for values[ip1] in g1(): |
| 1074 | for values[ip2] in g2(): |
| 1075 | yield values |
| 1076 | |
| 1077 | else: |
| 1078 | # At least 6 loop nests remain; peel off 3 and recurse for the |
| 1079 | # rest. |
| 1080 | for values[i] in g(): |
| 1081 | for values[ip1] in g1(): |
| 1082 | for values[ip2] in g2(): |
| 1083 | for x in _gen3(ip3): |
| 1084 | yield x |
| 1085 | |
| 1086 | for x in gen(0): |
| 1087 | yield x |
| 1088 | |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1089 | # And one more approach: For backtracking apps like the Knight's Tour |
| 1090 | # solver below, the number of backtracking levels can be enormous (one |
| 1091 | # level per square, for the Knight's Tour, so that e.g. a 100x100 board |
| 1092 | # needs 10,000 levels). In such cases Python is likely to run out of |
| 1093 | # stack space due to recursion. So here's a recursion-free version of |
| 1094 | # conjoin too. |
| 1095 | # NOTE WELL: This allows large problems to be solved with only trivial |
| 1096 | # demands on stack space. Without explicitly resumable generators, this is |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1097 | # much harder to achieve. OTOH, this is much slower (up to a factor of 2) |
| 1098 | # than the fancy unrolled recursive conjoin. |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1099 | |
| 1100 | def flat_conjoin(gs): # rename to conjoin to run tests with this instead |
| 1101 | n = len(gs) |
| 1102 | values = [None] * n |
| 1103 | iters = [None] * n |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1104 | _StopIteration = StopIteration # make local because caught a *lot* |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1105 | i = 0 |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1106 | while 1: |
| 1107 | # Descend. |
| 1108 | try: |
| 1109 | while i < n: |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 1110 | it = iters[i] = gs[i]().__next__ |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1111 | values[i] = it() |
| 1112 | i += 1 |
| 1113 | except _StopIteration: |
| 1114 | pass |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1115 | else: |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1116 | assert i == n |
| 1117 | yield values |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1118 | |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1119 | # Backtrack until an older iterator can be resumed. |
| 1120 | i -= 1 |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1121 | while i >= 0: |
| 1122 | try: |
| 1123 | values[i] = iters[i]() |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1124 | # Success! Start fresh at next level. |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1125 | i += 1 |
| 1126 | break |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1127 | except _StopIteration: |
| 1128 | # Continue backtracking. |
| 1129 | i -= 1 |
| 1130 | else: |
| 1131 | assert i < 0 |
| 1132 | break |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1133 | |
Tim Peters | be4f0a7 | 2001-06-29 02:41:16 +0000 | [diff] [blame] | 1134 | # A conjoin-based N-Queens solver. |
| 1135 | |
| 1136 | class Queens: |
| 1137 | def __init__(self, n): |
| 1138 | self.n = n |
| 1139 | rangen = range(n) |
| 1140 | |
| 1141 | # Assign a unique int to each column and diagonal. |
| 1142 | # columns: n of those, range(n). |
| 1143 | # NW-SE diagonals: 2n-1 of these, i-j unique and invariant along |
| 1144 | # each, smallest i-j is 0-(n-1) = 1-n, so add n-1 to shift to 0- |
| 1145 | # based. |
| 1146 | # NE-SW diagonals: 2n-1 of these, i+j unique and invariant along |
| 1147 | # each, smallest i+j is 0, largest is 2n-2. |
| 1148 | |
| 1149 | # For each square, compute a bit vector of the columns and |
| 1150 | # diagonals it covers, and for each row compute a function that |
| 1151 | # generates the possiblities for the columns in that row. |
| 1152 | self.rowgenerators = [] |
| 1153 | for i in rangen: |
Guido van Rossum | e2a383d | 2007-01-15 16:59:06 +0000 | [diff] [blame] | 1154 | rowuses = [(1 << j) | # column ordinal |
| 1155 | (1 << (n + i-j + n-1)) | # NW-SE ordinal |
| 1156 | (1 << (n + 2*n-1 + i+j)) # NE-SW ordinal |
Tim Peters | be4f0a7 | 2001-06-29 02:41:16 +0000 | [diff] [blame] | 1157 | for j in rangen] |
| 1158 | |
| 1159 | def rowgen(rowuses=rowuses): |
| 1160 | for j in rangen: |
| 1161 | uses = rowuses[j] |
Tim Peters | c468fd2 | 2001-06-30 07:29:44 +0000 | [diff] [blame] | 1162 | if uses & self.used == 0: |
| 1163 | self.used |= uses |
| 1164 | yield j |
| 1165 | self.used &= ~uses |
Tim Peters | be4f0a7 | 2001-06-29 02:41:16 +0000 | [diff] [blame] | 1166 | |
| 1167 | self.rowgenerators.append(rowgen) |
| 1168 | |
| 1169 | # Generate solutions. |
| 1170 | def solve(self): |
| 1171 | self.used = 0 |
| 1172 | for row2col in conjoin(self.rowgenerators): |
| 1173 | yield row2col |
| 1174 | |
| 1175 | def printsolution(self, row2col): |
| 1176 | n = self.n |
| 1177 | assert n == len(row2col) |
| 1178 | sep = "+" + "-+" * n |
Guido van Rossum | be19ed7 | 2007-02-09 05:37:30 +0000 | [diff] [blame] | 1179 | print(sep) |
Tim Peters | be4f0a7 | 2001-06-29 02:41:16 +0000 | [diff] [blame] | 1180 | for i in range(n): |
| 1181 | squares = [" " for j in range(n)] |
| 1182 | squares[row2col[i]] = "Q" |
Guido van Rossum | be19ed7 | 2007-02-09 05:37:30 +0000 | [diff] [blame] | 1183 | print("|" + "|".join(squares) + "|") |
| 1184 | print(sep) |
Tim Peters | be4f0a7 | 2001-06-29 02:41:16 +0000 | [diff] [blame] | 1185 | |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1186 | # A conjoin-based Knight's Tour solver. This is pretty sophisticated |
| 1187 | # (e.g., when used with flat_conjoin above, and passing hard=1 to the |
| 1188 | # constructor, a 200x200 Knight's Tour was found quickly -- note that we're |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1189 | # creating 10s of thousands of generators then!), and is lengthy. |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1190 | |
| 1191 | class Knights: |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1192 | def __init__(self, m, n, hard=0): |
| 1193 | self.m, self.n = m, n |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1194 | |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1195 | # solve() will set up succs[i] to be a list of square #i's |
| 1196 | # successors. |
| 1197 | succs = self.succs = [] |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1198 | |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1199 | # Remove i0 from each of its successor's successor lists, i.e. |
| 1200 | # successors can't go back to i0 again. Return 0 if we can |
| 1201 | # detect this makes a solution impossible, else return 1. |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1202 | |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1203 | def remove_from_successors(i0, len=len): |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1204 | # If we remove all exits from a free square, we're dead: |
| 1205 | # even if we move to it next, we can't leave it again. |
| 1206 | # If we create a square with one exit, we must visit it next; |
| 1207 | # else somebody else will have to visit it, and since there's |
| 1208 | # only one adjacent, there won't be a way to leave it again. |
| 1209 | # Finelly, if we create more than one free square with a |
| 1210 | # single exit, we can only move to one of them next, leaving |
| 1211 | # the other one a dead end. |
| 1212 | ne0 = ne1 = 0 |
| 1213 | for i in succs[i0]: |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1214 | s = succs[i] |
| 1215 | s.remove(i0) |
| 1216 | e = len(s) |
| 1217 | if e == 0: |
| 1218 | ne0 += 1 |
| 1219 | elif e == 1: |
| 1220 | ne1 += 1 |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1221 | return ne0 == 0 and ne1 < 2 |
| 1222 | |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1223 | # Put i0 back in each of its successor's successor lists. |
| 1224 | |
| 1225 | def add_to_successors(i0): |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1226 | for i in succs[i0]: |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1227 | succs[i].append(i0) |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1228 | |
| 1229 | # Generate the first move. |
| 1230 | def first(): |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1231 | if m < 1 or n < 1: |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1232 | return |
| 1233 | |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1234 | # Since we're looking for a cycle, it doesn't matter where we |
| 1235 | # start. Starting in a corner makes the 2nd move easy. |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1236 | corner = self.coords2index(0, 0) |
| 1237 | remove_from_successors(corner) |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1238 | self.lastij = corner |
| 1239 | yield corner |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1240 | add_to_successors(corner) |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1241 | |
| 1242 | # Generate the second moves. |
| 1243 | def second(): |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1244 | corner = self.coords2index(0, 0) |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1245 | assert self.lastij == corner # i.e., we started in the corner |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1246 | if m < 3 or n < 3: |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1247 | return |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1248 | assert len(succs[corner]) == 2 |
| 1249 | assert self.coords2index(1, 2) in succs[corner] |
| 1250 | assert self.coords2index(2, 1) in succs[corner] |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1251 | # Only two choices. Whichever we pick, the other must be the |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1252 | # square picked on move m*n, as it's the only way to get back |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1253 | # to (0, 0). Save its index in self.final so that moves before |
| 1254 | # the last know it must be kept free. |
| 1255 | for i, j in (1, 2), (2, 1): |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1256 | this = self.coords2index(i, j) |
| 1257 | final = self.coords2index(3-i, 3-j) |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1258 | self.final = final |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1259 | |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1260 | remove_from_successors(this) |
| 1261 | succs[final].append(corner) |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1262 | self.lastij = this |
| 1263 | yield this |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1264 | succs[final].remove(corner) |
| 1265 | add_to_successors(this) |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1266 | |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1267 | # Generate moves 3 thru m*n-1. |
| 1268 | def advance(len=len): |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1269 | # If some successor has only one exit, must take it. |
| 1270 | # Else favor successors with fewer exits. |
| 1271 | candidates = [] |
| 1272 | for i in succs[self.lastij]: |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1273 | e = len(succs[i]) |
| 1274 | assert e > 0, "else remove_from_successors() pruning flawed" |
| 1275 | if e == 1: |
| 1276 | candidates = [(e, i)] |
| 1277 | break |
| 1278 | candidates.append((e, i)) |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1279 | else: |
| 1280 | candidates.sort() |
| 1281 | |
| 1282 | for e, i in candidates: |
| 1283 | if i != self.final: |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1284 | if remove_from_successors(i): |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1285 | self.lastij = i |
| 1286 | yield i |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1287 | add_to_successors(i) |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1288 | |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1289 | # Generate moves 3 thru m*n-1. Alternative version using a |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1290 | # stronger (but more expensive) heuristic to order successors. |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1291 | # Since the # of backtracking levels is m*n, a poor move early on |
| 1292 | # can take eons to undo. Smallest square board for which this |
| 1293 | # matters a lot is 52x52. |
| 1294 | def advance_hard(vmid=(m-1)/2.0, hmid=(n-1)/2.0, len=len): |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1295 | # If some successor has only one exit, must take it. |
| 1296 | # Else favor successors with fewer exits. |
| 1297 | # Break ties via max distance from board centerpoint (favor |
| 1298 | # corners and edges whenever possible). |
| 1299 | candidates = [] |
| 1300 | for i in succs[self.lastij]: |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1301 | e = len(succs[i]) |
| 1302 | assert e > 0, "else remove_from_successors() pruning flawed" |
| 1303 | if e == 1: |
| 1304 | candidates = [(e, 0, i)] |
| 1305 | break |
| 1306 | i1, j1 = self.index2coords(i) |
| 1307 | d = (i1 - vmid)**2 + (j1 - hmid)**2 |
| 1308 | candidates.append((e, -d, i)) |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1309 | else: |
| 1310 | candidates.sort() |
| 1311 | |
| 1312 | for e, d, i in candidates: |
| 1313 | if i != self.final: |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1314 | if remove_from_successors(i): |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1315 | self.lastij = i |
| 1316 | yield i |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1317 | add_to_successors(i) |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1318 | |
| 1319 | # Generate the last move. |
| 1320 | def last(): |
| 1321 | assert self.final in succs[self.lastij] |
| 1322 | yield self.final |
| 1323 | |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1324 | if m*n < 4: |
| 1325 | self.squaregenerators = [first] |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1326 | else: |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1327 | self.squaregenerators = [first, second] + \ |
| 1328 | [hard and advance_hard or advance] * (m*n - 3) + \ |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1329 | [last] |
| 1330 | |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1331 | def coords2index(self, i, j): |
| 1332 | assert 0 <= i < self.m |
| 1333 | assert 0 <= j < self.n |
| 1334 | return i * self.n + j |
| 1335 | |
| 1336 | def index2coords(self, index): |
| 1337 | assert 0 <= index < self.m * self.n |
| 1338 | return divmod(index, self.n) |
| 1339 | |
| 1340 | def _init_board(self): |
| 1341 | succs = self.succs |
| 1342 | del succs[:] |
| 1343 | m, n = self.m, self.n |
| 1344 | c2i = self.coords2index |
| 1345 | |
| 1346 | offsets = [( 1, 2), ( 2, 1), ( 2, -1), ( 1, -2), |
| 1347 | (-1, -2), (-2, -1), (-2, 1), (-1, 2)] |
| 1348 | rangen = range(n) |
| 1349 | for i in range(m): |
| 1350 | for j in rangen: |
| 1351 | s = [c2i(i+io, j+jo) for io, jo in offsets |
| 1352 | if 0 <= i+io < m and |
| 1353 | 0 <= j+jo < n] |
| 1354 | succs.append(s) |
| 1355 | |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1356 | # Generate solutions. |
| 1357 | def solve(self): |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1358 | self._init_board() |
| 1359 | for x in conjoin(self.squaregenerators): |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1360 | yield x |
| 1361 | |
| 1362 | def printsolution(self, x): |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1363 | m, n = self.m, self.n |
| 1364 | assert len(x) == m*n |
| 1365 | w = len(str(m*n)) |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1366 | format = "%" + str(w) + "d" |
| 1367 | |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1368 | squares = [[None] * n for i in range(m)] |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1369 | k = 1 |
| 1370 | for i in x: |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1371 | i1, j1 = self.index2coords(i) |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1372 | squares[i1][j1] = format % k |
| 1373 | k += 1 |
| 1374 | |
| 1375 | sep = "+" + ("-" * w + "+") * n |
Guido van Rossum | be19ed7 | 2007-02-09 05:37:30 +0000 | [diff] [blame] | 1376 | print(sep) |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1377 | for i in range(m): |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1378 | row = squares[i] |
Guido van Rossum | be19ed7 | 2007-02-09 05:37:30 +0000 | [diff] [blame] | 1379 | print("|" + "|".join(row) + "|") |
| 1380 | print(sep) |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1381 | |
Tim Peters | be4f0a7 | 2001-06-29 02:41:16 +0000 | [diff] [blame] | 1382 | conjoin_tests = """ |
| 1383 | |
| 1384 | Generate the 3-bit binary numbers in order. This illustrates dumbest- |
| 1385 | possible use of conjoin, just to generate the full cross-product. |
| 1386 | |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1387 | >>> for c in conjoin([lambda: iter((0, 1))] * 3): |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 1388 | ... print(c) |
Tim Peters | be4f0a7 | 2001-06-29 02:41:16 +0000 | [diff] [blame] | 1389 | [0, 0, 0] |
| 1390 | [0, 0, 1] |
| 1391 | [0, 1, 0] |
| 1392 | [0, 1, 1] |
| 1393 | [1, 0, 0] |
| 1394 | [1, 0, 1] |
| 1395 | [1, 1, 0] |
| 1396 | [1, 1, 1] |
| 1397 | |
Tim Peters | c468fd2 | 2001-06-30 07:29:44 +0000 | [diff] [blame] | 1398 | For efficiency in typical backtracking apps, conjoin() yields the same list |
| 1399 | object each time. So if you want to save away a full account of its |
| 1400 | generated sequence, you need to copy its results. |
| 1401 | |
| 1402 | >>> def gencopy(iterator): |
| 1403 | ... for x in iterator: |
| 1404 | ... yield x[:] |
| 1405 | |
| 1406 | >>> for n in range(10): |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1407 | ... all = list(gencopy(conjoin([lambda: iter((0, 1))] * n))) |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 1408 | ... print(n, len(all), all[0] == [0] * n, all[-1] == [1] * n) |
Guido van Rossum | 77f6a65 | 2002-04-03 22:41:51 +0000 | [diff] [blame] | 1409 | 0 1 True True |
| 1410 | 1 2 True True |
| 1411 | 2 4 True True |
| 1412 | 3 8 True True |
| 1413 | 4 16 True True |
| 1414 | 5 32 True True |
| 1415 | 6 64 True True |
| 1416 | 7 128 True True |
| 1417 | 8 256 True True |
| 1418 | 9 512 True True |
Tim Peters | c468fd2 | 2001-06-30 07:29:44 +0000 | [diff] [blame] | 1419 | |
Tim Peters | be4f0a7 | 2001-06-29 02:41:16 +0000 | [diff] [blame] | 1420 | And run an 8-queens solver. |
| 1421 | |
| 1422 | >>> q = Queens(8) |
| 1423 | >>> LIMIT = 2 |
| 1424 | >>> count = 0 |
| 1425 | >>> for row2col in q.solve(): |
| 1426 | ... count += 1 |
| 1427 | ... if count <= LIMIT: |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 1428 | ... print("Solution", count) |
Tim Peters | be4f0a7 | 2001-06-29 02:41:16 +0000 | [diff] [blame] | 1429 | ... q.printsolution(row2col) |
| 1430 | Solution 1 |
| 1431 | +-+-+-+-+-+-+-+-+ |
| 1432 | |Q| | | | | | | | |
| 1433 | +-+-+-+-+-+-+-+-+ |
| 1434 | | | | | |Q| | | | |
| 1435 | +-+-+-+-+-+-+-+-+ |
| 1436 | | | | | | | | |Q| |
| 1437 | +-+-+-+-+-+-+-+-+ |
| 1438 | | | | | | |Q| | | |
| 1439 | +-+-+-+-+-+-+-+-+ |
| 1440 | | | |Q| | | | | | |
| 1441 | +-+-+-+-+-+-+-+-+ |
| 1442 | | | | | | | |Q| | |
| 1443 | +-+-+-+-+-+-+-+-+ |
| 1444 | | |Q| | | | | | | |
| 1445 | +-+-+-+-+-+-+-+-+ |
| 1446 | | | | |Q| | | | | |
| 1447 | +-+-+-+-+-+-+-+-+ |
| 1448 | Solution 2 |
| 1449 | +-+-+-+-+-+-+-+-+ |
| 1450 | |Q| | | | | | | | |
| 1451 | +-+-+-+-+-+-+-+-+ |
| 1452 | | | | | | |Q| | | |
| 1453 | +-+-+-+-+-+-+-+-+ |
| 1454 | | | | | | | | |Q| |
| 1455 | +-+-+-+-+-+-+-+-+ |
| 1456 | | | |Q| | | | | | |
| 1457 | +-+-+-+-+-+-+-+-+ |
| 1458 | | | | | | | |Q| | |
| 1459 | +-+-+-+-+-+-+-+-+ |
| 1460 | | | | |Q| | | | | |
| 1461 | +-+-+-+-+-+-+-+-+ |
| 1462 | | |Q| | | | | | | |
| 1463 | +-+-+-+-+-+-+-+-+ |
| 1464 | | | | | |Q| | | | |
| 1465 | +-+-+-+-+-+-+-+-+ |
| 1466 | |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 1467 | >>> print(count, "solutions in all.") |
Tim Peters | be4f0a7 | 2001-06-29 02:41:16 +0000 | [diff] [blame] | 1468 | 92 solutions in all. |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1469 | |
| 1470 | And run a Knight's Tour on a 10x10 board. Note that there are about |
| 1471 | 20,000 solutions even on a 6x6 board, so don't dare run this to exhaustion. |
| 1472 | |
Tim Peters | 9a8c8e2 | 2001-07-13 09:12:12 +0000 | [diff] [blame] | 1473 | >>> k = Knights(10, 10) |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1474 | >>> LIMIT = 2 |
| 1475 | >>> count = 0 |
| 1476 | >>> for x in k.solve(): |
| 1477 | ... count += 1 |
| 1478 | ... if count <= LIMIT: |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 1479 | ... print("Solution", count) |
unknown | 3156956 | 2001-07-04 22:11:22 +0000 | [diff] [blame] | 1480 | ... k.printsolution(x) |
| 1481 | ... else: |
| 1482 | ... break |
| 1483 | Solution 1 |
| 1484 | +---+---+---+---+---+---+---+---+---+---+ |
| 1485 | | 1| 58| 27| 34| 3| 40| 29| 10| 5| 8| |
| 1486 | +---+---+---+---+---+---+---+---+---+---+ |
| 1487 | | 26| 35| 2| 57| 28| 33| 4| 7| 30| 11| |
| 1488 | +---+---+---+---+---+---+---+---+---+---+ |
| 1489 | | 59|100| 73| 36| 41| 56| 39| 32| 9| 6| |
| 1490 | +---+---+---+---+---+---+---+---+---+---+ |
| 1491 | | 74| 25| 60| 55| 72| 37| 42| 49| 12| 31| |
| 1492 | +---+---+---+---+---+---+---+---+---+---+ |
| 1493 | | 61| 86| 99| 76| 63| 52| 47| 38| 43| 50| |
| 1494 | +---+---+---+---+---+---+---+---+---+---+ |
| 1495 | | 24| 75| 62| 85| 54| 71| 64| 51| 48| 13| |
| 1496 | +---+---+---+---+---+---+---+---+---+---+ |
| 1497 | | 87| 98| 91| 80| 77| 84| 53| 46| 65| 44| |
| 1498 | +---+---+---+---+---+---+---+---+---+---+ |
| 1499 | | 90| 23| 88| 95| 70| 79| 68| 83| 14| 17| |
| 1500 | +---+---+---+---+---+---+---+---+---+---+ |
| 1501 | | 97| 92| 21| 78| 81| 94| 19| 16| 45| 66| |
| 1502 | +---+---+---+---+---+---+---+---+---+---+ |
| 1503 | | 22| 89| 96| 93| 20| 69| 82| 67| 18| 15| |
| 1504 | +---+---+---+---+---+---+---+---+---+---+ |
| 1505 | Solution 2 |
| 1506 | +---+---+---+---+---+---+---+---+---+---+ |
| 1507 | | 1| 58| 27| 34| 3| 40| 29| 10| 5| 8| |
| 1508 | +---+---+---+---+---+---+---+---+---+---+ |
| 1509 | | 26| 35| 2| 57| 28| 33| 4| 7| 30| 11| |
| 1510 | +---+---+---+---+---+---+---+---+---+---+ |
| 1511 | | 59|100| 73| 36| 41| 56| 39| 32| 9| 6| |
| 1512 | +---+---+---+---+---+---+---+---+---+---+ |
| 1513 | | 74| 25| 60| 55| 72| 37| 42| 49| 12| 31| |
| 1514 | +---+---+---+---+---+---+---+---+---+---+ |
| 1515 | | 61| 86| 99| 76| 63| 52| 47| 38| 43| 50| |
| 1516 | +---+---+---+---+---+---+---+---+---+---+ |
| 1517 | | 24| 75| 62| 85| 54| 71| 64| 51| 48| 13| |
| 1518 | +---+---+---+---+---+---+---+---+---+---+ |
| 1519 | | 87| 98| 89| 80| 77| 84| 53| 46| 65| 44| |
| 1520 | +---+---+---+---+---+---+---+---+---+---+ |
| 1521 | | 90| 23| 92| 95| 70| 79| 68| 83| 14| 17| |
| 1522 | +---+---+---+---+---+---+---+---+---+---+ |
| 1523 | | 97| 88| 21| 78| 81| 94| 19| 16| 45| 66| |
| 1524 | +---+---+---+---+---+---+---+---+---+---+ |
| 1525 | | 22| 91| 96| 93| 20| 69| 82| 67| 18| 15| |
| 1526 | +---+---+---+---+---+---+---+---+---+---+ |
Tim Peters | be4f0a7 | 2001-06-29 02:41:16 +0000 | [diff] [blame] | 1527 | """ |
| 1528 | |
Fred Drake | 56d1266 | 2002-08-09 18:37:10 +0000 | [diff] [blame] | 1529 | weakref_tests = """\ |
| 1530 | Generators are weakly referencable: |
| 1531 | |
| 1532 | >>> import weakref |
| 1533 | >>> def gen(): |
| 1534 | ... yield 'foo!' |
| 1535 | ... |
| 1536 | >>> wr = weakref.ref(gen) |
| 1537 | >>> wr() is gen |
| 1538 | True |
| 1539 | >>> p = weakref.proxy(gen) |
| 1540 | |
| 1541 | Generator-iterators are weakly referencable as well: |
| 1542 | |
| 1543 | >>> gi = gen() |
| 1544 | >>> wr = weakref.ref(gi) |
| 1545 | >>> wr() is gi |
| 1546 | True |
| 1547 | >>> p = weakref.proxy(gi) |
| 1548 | >>> list(p) |
| 1549 | ['foo!'] |
| 1550 | |
| 1551 | """ |
| 1552 | |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1553 | coroutine_tests = """\ |
| 1554 | Sending a value into a started generator: |
| 1555 | |
| 1556 | >>> def f(): |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 1557 | ... print((yield 1)) |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1558 | ... yield 2 |
| 1559 | >>> g = f() |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 1560 | >>> next(g) |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1561 | 1 |
| 1562 | >>> g.send(42) |
| 1563 | 42 |
| 1564 | 2 |
| 1565 | |
| 1566 | Sending a value into a new generator produces a TypeError: |
| 1567 | |
| 1568 | >>> f().send("foo") |
| 1569 | Traceback (most recent call last): |
| 1570 | ... |
| 1571 | TypeError: can't send non-None value to a just-started generator |
| 1572 | |
| 1573 | |
| 1574 | Yield by itself yields None: |
| 1575 | |
| 1576 | >>> def f(): yield |
| 1577 | >>> list(f()) |
| 1578 | [None] |
| 1579 | |
| 1580 | |
| 1581 | |
| 1582 | An obscene abuse of a yield expression within a generator expression: |
| 1583 | |
| 1584 | >>> list((yield 21) for i in range(4)) |
| 1585 | [21, None, 21, None, 21, None, 21, None] |
| 1586 | |
| 1587 | And a more sane, but still weird usage: |
| 1588 | |
| 1589 | >>> def f(): list(i for i in [(yield 26)]) |
| 1590 | >>> type(f()) |
Martin v. Löwis | 250ad61 | 2008-04-07 05:43:42 +0000 | [diff] [blame] | 1591 | <class 'generator'> |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1592 | |
| 1593 | |
Thomas Wouters | 0e3f591 | 2006-08-11 14:57:12 +0000 | [diff] [blame] | 1594 | A yield expression with augmented assignment. |
| 1595 | |
| 1596 | >>> def coroutine(seq): |
| 1597 | ... count = 0 |
| 1598 | ... while count < 200: |
| 1599 | ... count += yield |
| 1600 | ... seq.append(count) |
| 1601 | >>> seq = [] |
| 1602 | >>> c = coroutine(seq) |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 1603 | >>> next(c) |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 1604 | >>> print(seq) |
Thomas Wouters | 0e3f591 | 2006-08-11 14:57:12 +0000 | [diff] [blame] | 1605 | [] |
| 1606 | >>> c.send(10) |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 1607 | >>> print(seq) |
Thomas Wouters | 0e3f591 | 2006-08-11 14:57:12 +0000 | [diff] [blame] | 1608 | [10] |
| 1609 | >>> c.send(10) |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 1610 | >>> print(seq) |
Thomas Wouters | 0e3f591 | 2006-08-11 14:57:12 +0000 | [diff] [blame] | 1611 | [10, 20] |
| 1612 | >>> c.send(10) |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 1613 | >>> print(seq) |
Thomas Wouters | 0e3f591 | 2006-08-11 14:57:12 +0000 | [diff] [blame] | 1614 | [10, 20, 30] |
| 1615 | |
| 1616 | |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1617 | Check some syntax errors for yield expressions: |
| 1618 | |
| 1619 | >>> f=lambda: (yield 1),(yield 2) |
| 1620 | Traceback (most recent call last): |
| 1621 | ... |
Guido van Rossum | 33d2689 | 2007-08-05 15:29:28 +0000 | [diff] [blame] | 1622 | SyntaxError: 'yield' outside function |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1623 | |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1624 | >>> def f(): x = yield = y |
| 1625 | Traceback (most recent call last): |
| 1626 | ... |
Guido van Rossum | 33d2689 | 2007-08-05 15:29:28 +0000 | [diff] [blame] | 1627 | SyntaxError: assignment to yield expression not possible |
Thomas Wouters | 0e3f591 | 2006-08-11 14:57:12 +0000 | [diff] [blame] | 1628 | |
| 1629 | >>> def f(): (yield bar) = y |
| 1630 | Traceback (most recent call last): |
| 1631 | ... |
Guido van Rossum | 33d2689 | 2007-08-05 15:29:28 +0000 | [diff] [blame] | 1632 | SyntaxError: can't assign to yield expression |
Thomas Wouters | 0e3f591 | 2006-08-11 14:57:12 +0000 | [diff] [blame] | 1633 | |
| 1634 | >>> def f(): (yield bar) += y |
| 1635 | Traceback (most recent call last): |
| 1636 | ... |
Benjamin Peterson | 87c8d87 | 2009-06-11 22:54:11 +0000 | [diff] [blame] | 1637 | SyntaxError: can't assign to yield expression |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1638 | |
| 1639 | |
| 1640 | Now check some throw() conditions: |
| 1641 | |
| 1642 | >>> def f(): |
| 1643 | ... while True: |
| 1644 | ... try: |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 1645 | ... print((yield)) |
Guido van Rossum | b940e11 | 2007-01-10 16:19:56 +0000 | [diff] [blame] | 1646 | ... except ValueError as v: |
Guido van Rossum | c420b2f | 2007-02-09 22:09:01 +0000 | [diff] [blame] | 1647 | ... print("caught ValueError (%s)" % (v)) |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1648 | >>> import sys |
| 1649 | >>> g = f() |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 1650 | >>> next(g) |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1651 | |
| 1652 | >>> g.throw(ValueError) # type only |
| 1653 | caught ValueError () |
| 1654 | |
| 1655 | >>> g.throw(ValueError("xyz")) # value only |
| 1656 | caught ValueError (xyz) |
| 1657 | |
| 1658 | >>> g.throw(ValueError, ValueError(1)) # value+matching type |
| 1659 | caught ValueError (1) |
| 1660 | |
| 1661 | >>> g.throw(ValueError, TypeError(1)) # mismatched type, rewrapped |
| 1662 | caught ValueError (1) |
| 1663 | |
Thomas Wouters | 49fd7fa | 2006-04-21 10:40:58 +0000 | [diff] [blame] | 1664 | >>> g.throw(ValueError, ValueError(1), None) # explicit None traceback |
| 1665 | caught ValueError (1) |
| 1666 | |
Tim Peters | e9fe7e0 | 2005-08-07 03:04:58 +0000 | [diff] [blame] | 1667 | >>> g.throw(ValueError(1), "foo") # bad args |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1668 | Traceback (most recent call last): |
| 1669 | ... |
| 1670 | TypeError: instance exception may not have a separate value |
| 1671 | |
Tim Peters | e9fe7e0 | 2005-08-07 03:04:58 +0000 | [diff] [blame] | 1672 | >>> g.throw(ValueError, "foo", 23) # bad args |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1673 | Traceback (most recent call last): |
| 1674 | ... |
| 1675 | TypeError: throw() third argument must be a traceback object |
| 1676 | |
Guido van Rossum | bf12cdb | 2006-08-17 20:24:18 +0000 | [diff] [blame] | 1677 | >>> g.throw("abc") |
| 1678 | Traceback (most recent call last): |
| 1679 | ... |
| 1680 | TypeError: exceptions must be classes or instances deriving from BaseException, not str |
| 1681 | |
| 1682 | >>> g.throw(0) |
| 1683 | Traceback (most recent call last): |
| 1684 | ... |
| 1685 | TypeError: exceptions must be classes or instances deriving from BaseException, not int |
| 1686 | |
| 1687 | >>> g.throw(list) |
| 1688 | Traceback (most recent call last): |
| 1689 | ... |
| 1690 | TypeError: exceptions must be classes or instances deriving from BaseException, not type |
| 1691 | |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1692 | >>> def throw(g,exc): |
| 1693 | ... try: |
| 1694 | ... raise exc |
| 1695 | ... except: |
| 1696 | ... g.throw(*sys.exc_info()) |
Tim Peters | e9fe7e0 | 2005-08-07 03:04:58 +0000 | [diff] [blame] | 1697 | >>> throw(g,ValueError) # do it with traceback included |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1698 | caught ValueError () |
| 1699 | |
| 1700 | >>> g.send(1) |
| 1701 | 1 |
| 1702 | |
Tim Peters | e9fe7e0 | 2005-08-07 03:04:58 +0000 | [diff] [blame] | 1703 | >>> throw(g,TypeError) # terminate the generator |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1704 | Traceback (most recent call last): |
| 1705 | ... |
| 1706 | TypeError |
| 1707 | |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 1708 | >>> print(g.gi_frame) |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1709 | None |
| 1710 | |
| 1711 | >>> g.send(2) |
| 1712 | Traceback (most recent call last): |
| 1713 | ... |
| 1714 | StopIteration |
| 1715 | |
Tim Peters | e9fe7e0 | 2005-08-07 03:04:58 +0000 | [diff] [blame] | 1716 | >>> g.throw(ValueError,6) # throw on closed generator |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1717 | Traceback (most recent call last): |
| 1718 | ... |
| 1719 | ValueError: 6 |
| 1720 | |
Tim Peters | e9fe7e0 | 2005-08-07 03:04:58 +0000 | [diff] [blame] | 1721 | >>> f().throw(ValueError,7) # throw on just-opened generator |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1722 | Traceback (most recent call last): |
| 1723 | ... |
| 1724 | ValueError: 7 |
| 1725 | |
Antoine Pitrou | 551ba20 | 2011-10-18 16:40:50 +0200 | [diff] [blame] | 1726 | Plain "raise" inside a generator should preserve the traceback (#13188). |
| 1727 | The traceback should have 3 levels: |
| 1728 | - g.throw() |
| 1729 | - f() |
| 1730 | - 1/0 |
| 1731 | |
| 1732 | >>> def f(): |
| 1733 | ... try: |
| 1734 | ... yield |
| 1735 | ... except: |
| 1736 | ... raise |
| 1737 | >>> g = f() |
| 1738 | >>> try: |
| 1739 | ... 1/0 |
| 1740 | ... except ZeroDivisionError as v: |
| 1741 | ... try: |
| 1742 | ... g.throw(v) |
| 1743 | ... except Exception as w: |
| 1744 | ... tb = w.__traceback__ |
| 1745 | >>> levels = 0 |
| 1746 | >>> while tb: |
| 1747 | ... levels += 1 |
| 1748 | ... tb = tb.tb_next |
| 1749 | >>> levels |
| 1750 | 3 |
| 1751 | |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1752 | Now let's try closing a generator: |
| 1753 | |
| 1754 | >>> def f(): |
| 1755 | ... try: yield |
| 1756 | ... except GeneratorExit: |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 1757 | ... print("exiting") |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1758 | |
| 1759 | >>> g = f() |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 1760 | >>> next(g) |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1761 | >>> g.close() |
| 1762 | exiting |
| 1763 | >>> g.close() # should be no-op now |
| 1764 | |
| 1765 | >>> f().close() # close on just-opened generator should be fine |
| 1766 | |
Tim Peters | e9fe7e0 | 2005-08-07 03:04:58 +0000 | [diff] [blame] | 1767 | >>> def f(): yield # an even simpler generator |
| 1768 | >>> f().close() # close before opening |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1769 | >>> g = f() |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 1770 | >>> next(g) |
Tim Peters | e9fe7e0 | 2005-08-07 03:04:58 +0000 | [diff] [blame] | 1771 | >>> g.close() # close normally |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1772 | |
| 1773 | And finalization: |
| 1774 | |
| 1775 | >>> def f(): |
| 1776 | ... try: yield |
| 1777 | ... finally: |
Guido van Rossum | 7131f84 | 2007-02-09 20:13:25 +0000 | [diff] [blame] | 1778 | ... print("exiting") |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1779 | |
| 1780 | >>> g = f() |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 1781 | >>> next(g) |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1782 | >>> del g |
| 1783 | exiting |
| 1784 | |
| 1785 | |
Christian Heimes | cbf3b5c | 2007-12-03 21:02:03 +0000 | [diff] [blame] | 1786 | GeneratorExit is not caught by except Exception: |
| 1787 | |
| 1788 | >>> def f(): |
| 1789 | ... try: yield |
| 1790 | ... except Exception: |
| 1791 | ... print('except') |
| 1792 | ... finally: |
| 1793 | ... print('finally') |
| 1794 | |
| 1795 | >>> g = f() |
| 1796 | >>> next(g) |
| 1797 | >>> del g |
| 1798 | finally |
| 1799 | |
| 1800 | |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1801 | Now let's try some ill-behaved generators: |
| 1802 | |
| 1803 | >>> def f(): |
| 1804 | ... try: yield |
| 1805 | ... except GeneratorExit: |
| 1806 | ... yield "foo!" |
| 1807 | >>> g = f() |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 1808 | >>> next(g) |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1809 | >>> g.close() |
| 1810 | Traceback (most recent call last): |
| 1811 | ... |
| 1812 | RuntimeError: generator ignored GeneratorExit |
| 1813 | >>> g.close() |
| 1814 | |
| 1815 | |
| 1816 | Our ill-behaved code should be invoked during GC: |
| 1817 | |
Guido van Rossum | 34d1928 | 2007-08-09 01:03:29 +0000 | [diff] [blame] | 1818 | >>> import sys, io |
| 1819 | >>> old, sys.stderr = sys.stderr, io.StringIO() |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1820 | >>> g = f() |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 1821 | >>> next(g) |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1822 | >>> del g |
Andrew Svetlov | 76bcff2 | 2012-11-03 15:56:05 +0200 | [diff] [blame] | 1823 | >>> "RuntimeError: generator ignored GeneratorExit" in sys.stderr.getvalue() |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1824 | True |
| 1825 | >>> sys.stderr = old |
| 1826 | |
| 1827 | |
| 1828 | And errors thrown during closing should propagate: |
| 1829 | |
| 1830 | >>> def f(): |
| 1831 | ... try: yield |
| 1832 | ... except GeneratorExit: |
| 1833 | ... raise TypeError("fie!") |
| 1834 | >>> g = f() |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 1835 | >>> next(g) |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1836 | >>> g.close() |
| 1837 | Traceback (most recent call last): |
| 1838 | ... |
| 1839 | TypeError: fie! |
| 1840 | |
| 1841 | |
| 1842 | Ensure that various yield expression constructs make their |
| 1843 | enclosing function a generator: |
| 1844 | |
| 1845 | >>> def f(): x += yield |
| 1846 | >>> type(f()) |
Martin v. Löwis | 250ad61 | 2008-04-07 05:43:42 +0000 | [diff] [blame] | 1847 | <class 'generator'> |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1848 | |
| 1849 | >>> def f(): x = yield |
| 1850 | >>> type(f()) |
Martin v. Löwis | 250ad61 | 2008-04-07 05:43:42 +0000 | [diff] [blame] | 1851 | <class 'generator'> |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1852 | |
| 1853 | >>> def f(): lambda x=(yield): 1 |
| 1854 | >>> type(f()) |
Martin v. Löwis | 250ad61 | 2008-04-07 05:43:42 +0000 | [diff] [blame] | 1855 | <class 'generator'> |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1856 | |
| 1857 | >>> def f(): x=(i for i in (yield) if (yield)) |
| 1858 | >>> type(f()) |
Martin v. Löwis | 250ad61 | 2008-04-07 05:43:42 +0000 | [diff] [blame] | 1859 | <class 'generator'> |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1860 | |
| 1861 | >>> def f(d): d[(yield "a")] = d[(yield "b")] = 27 |
| 1862 | >>> data = [1,2] |
| 1863 | >>> g = f(data) |
| 1864 | >>> type(g) |
Martin v. Löwis | 250ad61 | 2008-04-07 05:43:42 +0000 | [diff] [blame] | 1865 | <class 'generator'> |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1866 | >>> g.send(None) |
| 1867 | 'a' |
| 1868 | >>> data |
| 1869 | [1, 2] |
| 1870 | >>> g.send(0) |
| 1871 | 'b' |
| 1872 | >>> data |
| 1873 | [27, 2] |
| 1874 | >>> try: g.send(1) |
| 1875 | ... except StopIteration: pass |
| 1876 | >>> data |
| 1877 | [27, 27] |
| 1878 | |
| 1879 | """ |
| 1880 | |
Thomas Wouters | 49fd7fa | 2006-04-21 10:40:58 +0000 | [diff] [blame] | 1881 | refleaks_tests = """ |
| 1882 | Prior to adding cycle-GC support to itertools.tee, this code would leak |
| 1883 | references. We add it to the standard suite so the routine refleak-tests |
| 1884 | would trigger if it starts being uncleanable again. |
| 1885 | |
| 1886 | >>> import itertools |
| 1887 | >>> def leak(): |
| 1888 | ... class gen: |
| 1889 | ... def __iter__(self): |
| 1890 | ... return self |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 1891 | ... def __next__(self): |
Thomas Wouters | 49fd7fa | 2006-04-21 10:40:58 +0000 | [diff] [blame] | 1892 | ... return self.item |
| 1893 | ... g = gen() |
| 1894 | ... head, tail = itertools.tee(g) |
| 1895 | ... g.item = head |
| 1896 | ... return head |
| 1897 | >>> it = leak() |
| 1898 | |
| 1899 | Make sure to also test the involvement of the tee-internal teedataobject, |
| 1900 | which stores returned items. |
| 1901 | |
Georg Brandl | a18af4e | 2007-04-21 15:47:16 +0000 | [diff] [blame] | 1902 | >>> item = next(it) |
Thomas Wouters | 49fd7fa | 2006-04-21 10:40:58 +0000 | [diff] [blame] | 1903 | |
| 1904 | |
| 1905 | |
| 1906 | This test leaked at one point due to generator finalization/destruction. |
| 1907 | It was copied from Lib/test/leakers/test_generator_cycle.py before the file |
| 1908 | was removed. |
| 1909 | |
| 1910 | >>> def leak(): |
| 1911 | ... def gen(): |
| 1912 | ... while True: |
| 1913 | ... yield g |
| 1914 | ... g = gen() |
| 1915 | |
| 1916 | >>> leak() |
| 1917 | |
| 1918 | |
| 1919 | |
| 1920 | This test isn't really generator related, but rather exception-in-cleanup |
| 1921 | related. The coroutine tests (above) just happen to cause an exception in |
| 1922 | the generator's __del__ (tp_del) method. We can also test for this |
| 1923 | explicitly, without generators. We do have to redirect stderr to avoid |
| 1924 | printing warnings and to doublecheck that we actually tested what we wanted |
| 1925 | to test. |
| 1926 | |
Guido van Rossum | 34d1928 | 2007-08-09 01:03:29 +0000 | [diff] [blame] | 1927 | >>> import sys, io |
Thomas Wouters | 49fd7fa | 2006-04-21 10:40:58 +0000 | [diff] [blame] | 1928 | >>> old = sys.stderr |
| 1929 | >>> try: |
Guido van Rossum | 34d1928 | 2007-08-09 01:03:29 +0000 | [diff] [blame] | 1930 | ... sys.stderr = io.StringIO() |
Thomas Wouters | 49fd7fa | 2006-04-21 10:40:58 +0000 | [diff] [blame] | 1931 | ... class Leaker: |
| 1932 | ... def __del__(self): |
Andrew Svetlov | 76bcff2 | 2012-11-03 15:56:05 +0200 | [diff] [blame] | 1933 | ... def invoke(message): |
| 1934 | ... raise RuntimeError(message) |
| 1935 | ... invoke("test") |
Thomas Wouters | 49fd7fa | 2006-04-21 10:40:58 +0000 | [diff] [blame] | 1936 | ... |
| 1937 | ... l = Leaker() |
| 1938 | ... del l |
| 1939 | ... err = sys.stderr.getvalue().strip() |
Andrew Svetlov | 76bcff2 | 2012-11-03 15:56:05 +0200 | [diff] [blame] | 1940 | ... "Exception ignored in" in err |
| 1941 | ... "RuntimeError: test" in err |
| 1942 | ... "Traceback" in err |
| 1943 | ... "in invoke" in err |
Thomas Wouters | 49fd7fa | 2006-04-21 10:40:58 +0000 | [diff] [blame] | 1944 | ... finally: |
| 1945 | ... sys.stderr = old |
| 1946 | True |
| 1947 | True |
Andrew Svetlov | 76bcff2 | 2012-11-03 15:56:05 +0200 | [diff] [blame] | 1948 | True |
| 1949 | True |
Thomas Wouters | 49fd7fa | 2006-04-21 10:40:58 +0000 | [diff] [blame] | 1950 | |
| 1951 | |
| 1952 | These refleak tests should perhaps be in a testfile of their own, |
| 1953 | test_generators just happened to be the test that drew these out. |
| 1954 | |
| 1955 | """ |
| 1956 | |
Tim Peters | f6ed074 | 2001-06-27 07:17:57 +0000 | [diff] [blame] | 1957 | __test__ = {"tut": tutorial_tests, |
| 1958 | "pep": pep_tests, |
| 1959 | "email": email_tests, |
| 1960 | "fun": fun_tests, |
Tim Peters | be4f0a7 | 2001-06-29 02:41:16 +0000 | [diff] [blame] | 1961 | "syntax": syntax_tests, |
Fred Drake | 56d1266 | 2002-08-09 18:37:10 +0000 | [diff] [blame] | 1962 | "conjoin": conjoin_tests, |
| 1963 | "weakref": weakref_tests, |
Phillip J. Eby | 0d6615f | 2005-08-02 00:46:46 +0000 | [diff] [blame] | 1964 | "coroutine": coroutine_tests, |
Thomas Wouters | 49fd7fa | 2006-04-21 10:40:58 +0000 | [diff] [blame] | 1965 | "refleaks": refleaks_tests, |
Fred Drake | 56d1266 | 2002-08-09 18:37:10 +0000 | [diff] [blame] | 1966 | } |
Tim Peters | 1def351 | 2001-06-23 20:27:04 +0000 | [diff] [blame] | 1967 | |
| 1968 | # Magic test name that regrtest.py invokes *after* importing this module. |
| 1969 | # This worms around a bootstrap problem. |
| 1970 | # Note that doctest and regrtest both look in sys.argv for a "-v" argument, |
| 1971 | # so this works as expected in both ways of running regrtest. |
Tim Peters | a0a6222 | 2001-09-09 06:12:01 +0000 | [diff] [blame] | 1972 | def test_main(verbose=None): |
Benjamin Peterson | ee8712c | 2008-05-20 21:35:26 +0000 | [diff] [blame] | 1973 | from test import support, test_generators |
Antoine Pitrou | 796564c | 2013-07-30 19:59:21 +0200 | [diff] [blame] | 1974 | support.run_unittest(__name__) |
Benjamin Peterson | ee8712c | 2008-05-20 21:35:26 +0000 | [diff] [blame] | 1975 | support.run_doctest(test_generators, verbose) |
Tim Peters | 1def351 | 2001-06-23 20:27:04 +0000 | [diff] [blame] | 1976 | |
| 1977 | # This part isn't needed for regrtest, but for running the test directly. |
| 1978 | if __name__ == "__main__": |
Tim Peters | a0a6222 | 2001-09-09 06:12:01 +0000 | [diff] [blame] | 1979 | test_main(1) |