On 2015-05-02 22:06, Cecil Westerhof wrote:
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.
Python _does_ have a secondary mechanism for cleaning up such reference
cycles using mark-and-sweep:
https://docs.python.org/3/reference/datamodel.html
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