Question about garbage collection

[Thomas Passin]

On 1/15/2024 9:47 PM, Akkana Peck via Python-list wrote:
> I wrote:
>>> Also be warned that some modules (particularly if they're based on libraries not written in Python) might not garbage collect, so you may need to use other methods of cleaning up after those objects.
> 
> Chris Angelico writes:
>> Got any examples of that?
> 
> The big one for me was gdk-pixbuf, part of GTK. When you do something like gtk.gdk.pixbuf_new_from_file(), there's a Python object that gets created, but there's also the underlying C code that allocates memory for the pixbuf. When the object went out of scope, the Python object was automatically garbage collected, but the pixbuf data leaked.

This kind of thing can happen with PyQt, also.  There are ways to 
minimize it but I don't know if you can ever be sure all Qt C++ objects 
will get deleted. It depends on the type of object and the circumstances.

> Calling gc.collect() caused the pixbuf data to be garbage collected too.
> 
> There used to be a post explaining this on the pygtk mailing list: the link was
> http://www.daa.com.au/pipermail/pygtk/2003-December/006499.html
> but that page is gone now and I can't seem to find any other archives of that list (it's not on archive.org either). And this was from GTK2; I never checked whether the extra gc.collect() is still necessary in GTK3, but I figure leaving it in doesn't hurt anything. I use pixbufs in a tiled map application, so there are a lot of small pixbufs being repeatedly read and then deallocated.
> 
>          ...Akkana