[Python-checkins] r45410 - python/trunk/Lib/test/test_generators.py

[tim.peters]

Author: tim.peters
Date: Sat Apr 15 03:48:57 2006
New Revision: 45410

Modified:
   python/trunk/Lib/test/test_generators.py
Log:
Changed comments to make sense now that the LazyList-based
examples no longer require any explicit closing to avoid
leaking.

That the tee-based examples still do is (I think) still a
mystery.  Part of the mystery is that gc.garbage remains
empty:  if it were the case that some generator in a trash
cycle said it needed finalization, suppressing collection
of that cycle, that generator _would_ show up in gc.garbage.

So this is acting more like, e.g., some tp_traverse slot
isn't visiting all the pointers it should (in which case
the skipped pointer(s) would act like an external root,
silently suppressing collection of everything reachable
from it(them)).


Modified: python/trunk/Lib/test/test_generators.py
==============================================================================
--- python/trunk/Lib/test/test_generators.py	(original)
+++ python/trunk/Lib/test/test_generators.py	Sat Apr 15 03:48:57 2006
@@ -700,11 +700,12 @@
 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
+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 the same kind of reference cycle as the m235()
-implementation above, and again we have to explicitly close the innermost
-generator to clean up the cycle.
+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.
 
 Ye olde Fibonacci generator, tee style.
 
@@ -730,6 +731,7 @@
 [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 = """