[Python-Dev] an alternative to embedding policy in PEP 418 (was: PEP 418: Add monotonic clock) (original) (raw)

Cameron Simpson cs at zip.com.au
Wed Apr 4 01:38:24 CEST 2012

On 03Apr2012 15:08, Ethan Furman <ethan at stoneleaf.us> wrote: | Cameron Simpson wrote: | > getclock already has two arguments - you can optionally hand it a clock | > list - that's used by monotonicclock() and hiresclock(). || def getclock(*flags, *, clocklist=None):

I presume that bare "*," is a typo. Both my python2 and python3 commands reject it.

[...] | wanted = 0 | for flag in flags: | wanted |= flag [...]

I could do this. I think I'm -0 on it, because it doesn't seem more expressive to my eye than the straight make-a-bitmask "|" form. Other opinions?

| Would need to make *flags change to the other *clock functions.

Yep.

| > The return of None is very deliberate. I want user specified fallback | > to be concise and easy. The example: | > clock = getclock(MONOTONIC|HIRES) or getclock(MONOTONIC) || Which would become: | clock = getclock(MONOTONIC, HIGHRES) or getclock(MONOTONIC) || +1 to returning None || > Exceptions are all very well when there is just one thing to do: parse | > this or fail, divide this by that or fail. If fact they're the very | > image of "do this one thing or FAIL". They are not such a good match for do | > this thing or that thing or this other thing.

Another thought that occurred in the shower was that get_clock() et al are inquiry functions, and returning None is very sensible there.

monotonic() et al are direct use functions, which should raise an exception if unavailable so that code like:

t0 = monotonic() ....... t1 = monotonic()

does not become littered with checks for special values like None.

I consider this additional reason to return None from get_clock().

Cheers,

Cameron Simpson <cs at zip.com.au> DoD#743 http://www.cskk.ezoshosting.com/cs/

DON'T DRINK SOAP! DILUTE DILUTE! OK! - on the label of Dr. Bronner's Castile Soap

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