[Python-Dev] Tweak to PEP 523 for storing a tuple in co_extra (original) (raw)

Brett Cannon brett at python.org
Sat Sep 3 20:20:47 EDT 2016

On Sat, 3 Sep 2016 at 16:55 Yury Selivanov <yselivanov.ml at gmail.com> wrote:

On 2016-09-03 4:13 PM, Chris Angelico wrote: > On Sun, Sep 4, 2016 at 8:03 AM, Yury Selivanov <yselivanov.ml at gmail.com> wrote: >> On 2016-09-03 12:27 PM, Brett Cannon wrote: >>> Below is the coextra section of PEP 523 with the update saying that >>> users are expected to put a tuple in the field for easier simultaneous use >>> of the field. >>> >>> Since the coextra discussions do not affect CPython itself I'm planning >>> on landing the changes stemming from the PEP probably on Monday. >> >> Tuples are immutable. If you have multiple coextra users then they will >> have to either mutate tuple (which isn't always possible, for instance, you >> can't increase size), or to replace it with another tuple. > Replace it, but only as they register themselves with a particular > function. Imagine a profiler doing something vaguely like this: "Replacing" makes it error prone to cache the pointer even for small periods of time. Defining coextra using Python C API forces us to acquire the GIL etc (aside from other performance penalties). Although we probably would recommend to use the GIL anyways, I'm not sure tuple really simplifies anything here. > > class FunctionStats: > def init(self): > self.info = [whatever, whatever, blah blah] > > def profile(func): > """Decorator to mark a function for profiling""" > func.code.coextra += (FunctionStats(),) > return func > > Tuple immutability impacts the initialization only. After that, you > just iterate over it. I wasn't aware we wanted to expose coextra to Python land.

We are most definitely not exposing the field to Python code. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.python.org/pipermail/python-dev/attachments/20160904/bab95736/attachment-0001.html>

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