WeakValueDict and threadsafety

[Duncan Booth]

Darren Dale <dsdale24 at gmail.com> wrote:

> I'm concerned that this is not actually thread-safe. When I no longer
> hold strong references to an instance of data, at some point the
> garbage collector will kick in and remove that entry from my registry.
> How can I ensure the garbage collection process does not modify the
> registry while I'm holding the lock?

You can't, but it shouldn't matter.

So long as you have a strong reference in 'data' that particular object 
will continue to exist. Other entries in 'registry' might disappear while 
you are holding your lock but that shouldn't matter to you.

What is concerning though is that you are using `id(data)` as the key and 
then presumably storing that separately as your `oid` value. If the 
lifetime of the value stored as `oid` exceeds the lifetime of the strong 
references to `data` then you might get a new data value created with the 
same id as some previous value.

In other words I think there's a problem here, but nothing to do with the 
lock.

-- 
Duncan Booth