On 08/09/2012 21:06, Thomas Rachel wrote:
Am 19.08.2012 00:14 schrieb MRAB:
Can someone who is more familiar with the cycle detector and cycle
breaker, help prove or disprove the above?
In simple terms, when you create an immutable object it can contain
only references to pre-existing objects, but in order to create a cycle
you need to make an object refer to another which is created later, so
it's not possible to create a cycle out of immutable objects.
Yes, but if I add a list in-between, I can create a refcycle:
a = []
b = (a,)
a.append(b)
So b is a tuple consisting of one list which in turn contains b.
It is not a direct cycle, but an indirect one.
Or would that be detected via the list?
The quote was:
'''
...The tuple type does not implement a tp_clear function, because it’s
possible to prove that no reference cycle can be composed entirely of
tuples.
'''
Note: "composed entirely of tuples".
Or, in general, composed entirely of immutables.
Lists are not immutable, therefore the proof does not apply.
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