MemoryError hook in Python?

Question

Is there a way to globally trap MemoryError exceptions so that a library can clear out caches instead of letting a MemoryError be seen by user code?

I\'m developing

Answer 1

This is not a good way of handling memory management. By the time you see MemoryError, you're already in a critical state where the kernel is probably close to killing processes to free up memory, and on many systems you'll never see it because it'll go to swap or just OOM-kill your process rather than fail allocations.

The only recoverable case you're likely to see MemoryError is after trying to make a very large allocation that doesn't fit in available address space, only common on 32-bit systems.

If you want to have a cache that frees memory as needed for other allocations, it needs to not interface with errors, but with the allocator itself. This way, when you need to release memory for an allocation you'll know how much contiguous memory is needed, or else you'll be guessing blindly. It also means you can track memory allocations as they happen, so you can keep memory usage at a specific level, rather than letting it grow unfettered and then trying to recover when it gets too high.

I'd strongly suggest that for most applications this sort of caching behavior is overcomplicated, though--you're usually better off just using a set amount of memory for cache.