[Python-Dev] Deletion order when leaving a scope?
Josiah Carlson
jcarlson at uci.edu
Thu Jan 18 03:38:41 CET 2007
Larry Hastings <larry at hastings.org> wrote:
> I just ran a quickie experiment and determined: when leaving a scope,
> variables are deleted FIFO, aka in the same order they were created.
> This surprised me; I'd expected them to be deleted LIFO, aka last
> first. Why is it thus? Is this behavior an important feature or an
> irrelevant side-effect?
If you are talking about the locals in the scope of a function, it is an
artifact of how the locals array is created. That is to say, the locals
of a function are a flat array, and are decref'd in-order. That
ordering is the original assignment ordering in the function, which is
an artifact of how the compiler goes from local name -> FAST_LOCALS
index. I don't believe it is an "important feature", but to decref in
any other order would be silly and/or unintuitive.
- Josiah
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