diff options
Diffstat (limited to 'Lib/test/test_generators.py')
| -rw-r--r-- | Lib/test/test_generators.py | 23 | 
1 files changed, 6 insertions, 17 deletions
diff --git a/Lib/test/test_generators.py b/Lib/test/test_generators.py index 4b2ed8f..9f83343 100644 --- a/Lib/test/test_generators.py +++ b/Lib/test/test_generators.py @@ -668,10 +668,7 @@ concept, viz. produce the results only as needed instead of producing them  all and thereby wasting memory.  Thanks to itertools.tee, it is now clear "how to get the internal uses of -m235 to share a single generator". Unfortunately, using generators this way -creates a reference-cycle that the garbage collector (currently) can't clean -up, so we have to explicitly break the cycle (by calling the inner -generator's close() method) +m235 to share a single generator".  >>> from itertools import tee  >>> def m235(): @@ -683,9 +680,9 @@ generator's close() method)  ...             yield n  ...     m1 = _m235()  ...     m2, m3, m5, mRes = tee(m1, 4) -...     return m1.close, mRes +...     return mRes ->>> closer, it = m235() +>>> it = m235()  >>> for i in range(5):  ...     print firstn(it, 15)  [1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 16, 18, 20, 24] @@ -693,7 +690,6 @@ generator's close() method)  [81, 90, 96, 100, 108, 120, 125, 128, 135, 144, 150, 160, 162, 180, 192]  [200, 216, 225, 240, 243, 250, 256, 270, 288, 300, 320, 324, 360, 375, 384]  [400, 405, 432, 450, 480, 486, 500, 512, 540, 576, 600, 625, 640, 648, 675] ->>> closer()  The "tee" function does just what we want. It internally keeps a generated  result for as long as it has not been "consumed" from all of the duplicated @@ -701,11 +697,7 @@ iterators, whereupon it is deleted. You can therefore print the hamming  sequence during hours without increasing memory usage, or very little.  The beauty of it is that recursive running-after-their-tail FP algorithms -are quite straightforwardly expressed with this Python idiom. The problem is -that this creates an uncollectable reference cycle, and we have to explicitly -close the innermost generator to clean up the cycle. -XXX As of 14-Apr-2006, Tim doubts that anyone understands _why_ some cycle -XXX is uncollectable here. +are quite straightforwardly expressed with this Python idiom.  Ye olde Fibonacci generator, tee style. @@ -724,14 +716,11 @@ Ye olde Fibonacci generator, tee style.  ...  ...     realfib = _fib()  ...     fibHead, fibTail, fibRes = tee(realfib, 3) -...     return realfib.close, fibRes +...     return fibRes ->>> closer, fibber = fib() ->>> firstn(fibber, 17) +>>> firstn(fib(), 17)  [1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584] ->>> closer() -XXX Again the tee-based approach leaks without an explicit close().  """  leak_test1 = """  | 
