[Python-3000] PEP: Eliminate del (original) (raw)

Jim Jewett jimjjewett at gmail.com
Tue May 1 17:43:33 CEST 2007

On 5/1/07, Raymond Hettinger <python at rcn.com> wrote:

The alternative is to code the automatic finalization steps using weakref callbacks. For those used to using del, it takes a little while to learn the idiom but essentially the technique is hold a proxy or ref with a callback to a boundmethod for finalization: self.resource = resource = CreateResource() self.callbacks.append(proxy(resource, resource.closedown)) In this manner, all of the object's resources can be freed automatically when the object is collected. Note, that the callbacks only bind the resource object and not client object, so the client object can already have been collected and the teardown code can be run without risk of resurrecting the client (with a possibly invalid state).

That alternative is pretty ugly, and I think we found some cases where it required major rewriting. (I don't have them handy, but may end up searching for them again, if need be.)

A smaller change would be to add close (which covers most use cases), or even to give del the close semantics.

The key distinction is that close says to go ahead and break the cycle in an arbitrary location, rather than immortalizing it.

-jJ

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