Change in behaviour Python 3.7 > 3.8

[Frank Millman]

On 2020-02-07 1:06 PM, Barry Scott wrote:
> 
> 
>> On 7 Feb 2020, at 05:27, Frank Millman <frank at chagford.com> wrote:
>>
>> @Barry
>> I agree that __del__() is rarely useful, but I have not come up with an alternative to achieve what I want to do. My app is a long-running server, and creates many objects on-the-fly depending on user input. They should be short-lived, and be removed when they go out of scope, but I can concerned that I may leave a dangling reference somewhere that keeps one of them alive, resulting in a memory leak over time. Creating a _del__() method and displaying a message to say 'I am being deleted' has proved effective, and has in fact highlighted a few cases where there was a real problem.
> 
> I have faced the same problem with leaking of objects.
> 
> What I did was use the python gc to find all the objects.
> 
> First I call gc.collect() to clean up all the objects what can be deleted.
> Then I call gc.get_objects() to get a list of all the objects the gc is tracking.
> I process that list into a collections.Counter() with counts of each type of object
> that I call a snapshot.
> 
> By creating the snapshots at interesting times in the services life I can diff the
> snapshots and see how the object usage changes over time.
> 
> The software I work on has an admin HTTP interface used internally that I use to request
> snapshots white the service is running.
> 

This is really useful. I will experiment with this and try to 
incorporate it into my project.

Thanks very much.

Frank