On Thu, Oct 17, 2013 at 11:55 AM, Oscar Benjamin <oscar.j.benja...@gmail.com > wrote:
> On 17 October 2013 19:40, Xavier Morel <python-...@masklinn.net> wrote: > > I think there's already a significant split between context managers > > which handle the lifecycle of a local resource (file, transaction) and > > those which purport to locally alter global-ish state (cwd, > > decimal.localcontext, logging.captureWarnings, redirect_stdout). > > > > And the latter worries me (much more than the very localized behavior of > > suppress) because I don't see any way to implement them safely and > > correctly when mixing it with coroutines in today's Python (some of them > > aren't even thread-safe), all of that while I expect coroutines will see > > significantly more use in the very near future with yield from and > > tulip's promotion of coroutine-style async. > > I maybe misunderstanding how the coroutine-style async works but I > would have thought that it would be as simple as: don't use > global-state-restoring-context-managers around statements that yield > control (it would be simpler if there was a good term for describing > that kind of CM). That's simpler to implement and computationally > cheaper than e.g. the thread-local state used by the decimal module. > Context managers that actually save and restore *global* state are already not thread-safe, so concluding they are also not coroutine-safe (or task-safe?) seems a small step. I'd be more worried about context manager that use thread-local state -- there is no similar concept in Tulip. -- --Guido van Rossum (python.org/~guido)
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