[Python-Dev] PEP 550 v4 (original) (raw)

Yury Selivanov yselivanov.ml at gmail.com
Wed Sep 6 20:17:40 EDT 2017

On Wed, Sep 6, 2017 at 5:06 PM, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:

Nathaniel Smith wrote:

The implementation strategy changed radically between v1 and v2 because of considerations around generator (not coroutine) semantics. I'm not sure what more it can do to dispel these feelings :-). I can't say the changes have dispelled any feelings on my part. The implementation suggested in the PEP seems very complicated and messy. There are garbage collection issues, which it proposes using weak references to mitigate.

"messy" and "complicated" doesn't sound like a valuable feedback :(

There are no "garbage collection issues", sorry. The issue that we use weak references for is the same issue why threading.local() uses them:

def foo():
     var = ContextVar()
     var.set(1)

for _ in range(10**6): foo()

If 'var' is strongly referenced, we would have a bunch of them.

There is also apparently some issue with long chains building up and having to be periodically collapsed. None of this inspires confidence that we have the basic design right.

My approach wouldn't have any of those problems. The implementation would be a lot simpler.

Cool.

Yury

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