That's probably a tricky question, since CPython is also essentially the spec. PyPy talks a bit about this: http://doc.pypy.org/en/latest/cpython_differences.ht

That's probably a tricky question, since CPython is also essentially the spec. PyPy talks a bit about this: http://doc.pypy.org/en/latest/cpython_differences.html#differences-related-to-garbage-collection-strategies http://doc.pypy.org/en/latest/cpython_differences.html#diffe... That's true, since Python has reflection it can't easily optimize that case, whereas that's a powerful benefit of having a linear type system for tracking ownership like Swift or Rust. But early freeing (which Rust has and Python does not) is slightly different from deterministic freeing (which both have) is slightly different from guaranteed freeing (which CPython has and Rust does not).