Python: how to “kill” a class instance/object?

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Question :

Python: how to “kill” a class instance/object?

I want a Roach class to “die” when it reaches a certain amount of “hunger”, but I don’t know how to delete the instance. I may be making a mistake with my terminology, but what I mean to say is that I have a ton of “roaches” on the window and I want specific ones to disappear entirely.

I would show you the code, but it’s quite long. I have the Roach class being appended into a Mastermind classes roach population list.

Answer #1:

In general:

  • Each binding variable -> object increases internal object’s reference counter
  • there are several usual ways to decrease reference (dereference object -> variable binding):

    1. exiting block of code where variable was declared (used for the first time)
    2. destructing object will release references of all attributes/method variable -> object references
    3. calling del variable will also delete reference in the current context
  • after all references to one object are removed (counter==0) it becomes good candidate for garbage collection, but it is not guaranteed that it will be processed (reference here):

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. See the documentation
of the gc module for information on controlling the collection of
cyclic garbage. Other implementations act differently and CPython may
change. Do not depend on immediate finalization of objects when they
become unreachable (ex: always close files).

Answered By: Robert Lujo

Answer #2:

You cannot force a Python object to be deleted; it will be deleted when nothing references it (or when it’s in a cycle only referred to be the items in the cycle). You will have to tell your “Mastermind” to erase its reference.

del somemastermind.roaches[n]

Answer #3:

for i,roach in enumerate(roachpopulation_list)
        if roach.hunger == 100
            del roachpopulation_list[i]
            break

Remove the instance by deleting it from your population list (containing all the roach instances.

If your Roaches are Sprites created in Pygame, then a simple command of .kill would remove the instance.

Answered By: Beatrix Kidco

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