[Python-ideas] More details in MemoryError (original) (raw)

MRAB python at mrabarnett.plus.com
Tue Jan 22 19:36:07 CET 2013

On 2013-01-22 13:04, Chris Angelico wrote:

On Tue, Jan 22, 2013 at 11:42 PM, Steven D'Aprano <steve at pearwood.info> wrote:

Something like this could be used to decide whether or not to flush unimportant in-memory caches, compact data structures, etc., or just give up and exit. That's a nice idea, but unless the requested allocation was fairly large, there's a good chance you don't have room to allocate anything more. That may make it a bit tricky to do a compaction operation. But if there's some sort of "automatically freeable memory" (simple example: exception-triggered stack unwinding results in a whole bunch of locals disappearing), and you can stay within that, then you might be able to recover. Would require some tightrope-walking in the exception handler, but ought to be possible. FYI, allocating memory specially for such cases is sometimes called a "memory parachute".

I wonder whether you could have a subclass of MemoryError called LowMemoryError.

If allocation fails and there's a parachute, it would free the parachute and raise LowMemoryError. That would gave you a chance to tidy up before quitting or even, perhaps, free enough stuff to make a new parachute and continue working.

If allocation fails and there's no parachute, it would raise MemoryError as at present.

With LowMemoryError as a subclass of MemoryError, existing code would still work the same.

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