Here's another thing to consider re: completeness of language implementation: do we want to support weak referenced (weakref module)?

On one hand, it's niche feature used rarely enough. On the other hand, it's something which would pretty much help low-memory usage: ability to cache some object in memory, but safely and transparently free it if there's memory pressure.

But efficient implementation of weakrefs is expensive - each object need to grow to contain pointer to its associated weakref. Taking into account that weakrefs are rare, less runtime-efficient, but much more memory-efficient impl of having a separate mapping from obj to its weakref can be used.

Thoughts/comments are welcome.