[Python-Dev] PEP 567 v2 (original) (raw)

Guido van Rossum guido at python.org
Wed Jan 3 00:42:17 EST 2018

On Tue, Jan 2, 2018 at 4:51 PM, Victor Stinner <victor.stinner at gmail.com> wrote:

Why ContextVar.reset(token) does nothing at the second call with the same token? What is the purpose of Token.used? I guess that there is an use case to justify this behaviour.

reset() should have a result: true if the variable was restored to its previous state, false if reset() did nothing because the token was already used. And/Or Token should have a read-only "used" property.

That depends again on the use case. The only real purpose for reset() is to be able to write a context manager that sets and restores a context variable (like in with decimal.localcontext()). Handling double resets is about as useful as specifying what happens if exit is called twice.

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