[Python-Dev] PEP 550 v3 (original) (raw)

Yury Selivanov yselivanov.ml at gmail.com
Mon Aug 21 17:44:53 EDT 2017

On Mon, Aug 21, 2017 at 5:39 PM, Koos Zevenhoven <k7hoven at gmail.com> wrote: [..]

In the current version of the PEP, generators are initialized with an empty LogicalContext. When they are being iterated (started or resumed), their LogicalContext is pushed to the EC. When the iteration is stopped (or paused), they pop their LC from the EC.

Another quick one before I go: Do we really need to push and pop a LC on each next() call, even if it most likely will never be touched?

Yes, otherwise it will be hard to maintain the consistency of the stack.

There will be an optimization: if the LC is empty, we will push NULL to the stack, thus avoiding the cost of allocating an object.

I measured the overhead -- generators will become 0.5-1% slower in microbenchmarks, but only when they do pretty much nothing. If a generator contains more Python code than a bare "yield" expression, the overhead will be harder to detect.

Yury

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