[Python-Dev] Deletion order when leaving a scope? (original) (raw)

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.

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