Inner workings of this Python feature: Can a Python data structure reference itself?

Sat May 2 17:06:38 EDT 2015

Op Saturday 2 May 2015 22:17 CEST schreef Tim Chase:
> [dangit, had Control down when I hit <enter> and it sent
> prematurely]
>> On 2015年05月02日 13:02, vasudevram wrote:
>> http://jugad2.blogspot.in/2015/05/can-python-data-structure-reference.html
>>>> https://docs.python.org/2/reference/datamodel.html
>>>> and saw this excerpt:
>>>> [ CPython implementation detail: CPython currently uses a
>> reference-counting scheme with (optional) delayed
>> detection of cyclically linked garbage, which collects
>> most objects as soon as they become unreachable, but is
>> not guaranteed to collect garbage containing circular
>> references. ]
>>>> Not sure whether it is relevant to the topic at hand,
>> since, on the one hand, it uses the words "cyclically
>> linked", but on the other, it says "garbage collection".
>> The gotcha happens in a case where you do something like this:
>> lst = []
> lst.append(lst) # create a cycle
> del lst
>> This creates a cycle, then makes it unreachable, but the list is
> still referenced by itself, so the reference count never drops to
> zero (where it would get GC'd), and thus that item lingers around in
> memory.

Maybe look at Java? If my memory is correct, the JVM gc reclaims those
kind of things also.
-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof