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PEP 418: Cleanup after reintroduction of fallback=True

This commit is contained in:
Victor Stinner 2012-03-31 02:00:43 +02:00
parent 53fa07dcc6
commit 72a7239f0e
1 changed files with 16 additions and 20 deletions
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36
pep-0418.txt
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@ -82,10 +82,14 @@ Clock that cannot go backward, its rate is as steady as possible. Its rate may
be adjusted by NTP. The reference point of the returned value is undefined so be adjusted by NTP. The reference point of the returned value is undefined so
only the difference of consecutive calls is valid. only the difference of consecutive calls is valid.
It is not available on all platforms and may raise an OSError. It is not By default, it falls back to the system clock if no monotonic clock is
available on GNU/Hurd for example. available or if the monotonic clock failed, and so it cannot fail. If fallback
is False, it raises OSError if the monotonic clock failed and
NotImplementedError if the platform does not provide a monotonic clock (ex:
GNU/Hurd).
The monotonic clock may stop while the system is suspended. The elapsed time may or may not include time the system spends in sleep or
hibernation, it depends on the operating system.
Pseudo-code [#pseudo]_: :: Pseudo-code [#pseudo]_: ::
@ -151,6 +155,12 @@ Pseudo-code [#pseudo]_: ::
monotonic.clocks.append(time.CLOCK_HIGHRES) monotonic.clocks.append(time.CLOCK_HIGHRES)
monotonic.clocks.append(time.CLOCK_MONOTONIC) monotonic.clocks.append(time.CLOCK_MONOTONIC)
else:
def monotonic(fallback=True):
if not fallback:
raise NotImplementedError("you platform does not provide any monotonic clock")
return time.time()
On Windows, QueryPerformanceCounter() is not used even if it has a better On Windows, QueryPerformanceCounter() is not used even if it has a better
resolution than GetTickCount(). It is not reliable and has too much issues. resolution than GetTickCount(). It is not reliable and has too much issues.
@ -204,7 +214,7 @@ CLOCK_MONOTONIC_RAW 1 ns (*) No Stopp
gethrtime 1 ns (*) No Not stopped gethrtime 1 ns (*) No Not stopped
CLOCK_HIGHRES 1 ns (*) No ? CLOCK_HIGHRES 1 ns (*) No ?
CLOCK_MONOTONIC 1 ns (*) Yes on Linux Stopped on Linux CLOCK_MONOTONIC 1 ns (*) Yes on Linux Stopped on Linux
mach_absolute_time() 1 ns ? No ? mach_absolute_time() 1 ns (*) No ?
QueryPerformanceCounter() \- 0.3 ns - 5 ns No Accuracy issue QueryPerformanceCounter() \- 0.3 ns - 5 ns No Accuracy issue
GetTickCount[64]() 1 ms 1 ms - 15 ms No Include suspend time GetTickCount[64]() 1 ms 1 ms - 15 ms No Include suspend time
timeGetTime() 1 ms 1 ms - 15 ms No ? timeGetTime() 1 ms 1 ms - 15 ms No ?
@ -564,8 +574,8 @@ Read also the `time(7) manual page
Alternatives: API design Alternatives: API design
======================== ========================
time.highres() function name Name of the "monotonic or fallback" function name
---------------------------- -------------------------------------------------
Other names were proposed: Other names were proposed:
@ -578,20 +588,6 @@ Other names were proposed:
chances with a best-effect clock." chances with a best-effect clock."
* time.wallclock() * time.wallclock()
One function with a flag: time.monotonic(strict=False)
------------------------------------------------------
* time.monotonic(strict=False) falls back to the system clock if no monotonic
clock is available or if the monotonic clock failed.
* time.monotonic(strict=True) raises OSError if monotonic clock fails and
NotImplementedError if the system does not provide a monotonic clock
"A keyword argument that gets passed as a constant in the caller is usually
poor API."
Raising NotImplementedError for a function is something uncommon in Python and
should be avoided.
One function, no flag One function, no flag
--------------------- ---------------------