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

[Cecil Westerhof]

Op Saturday 2 May 2015 22:17 CEST schreef Tim Chase:

> [dangit, had Control down when I hit <enter> and it sent
> prematurely]
>
> On 2015-05-02 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