[issue10278] add time.wallclock() method

[STINNER Victor]

STINNER Victor <victor.stinner at haypocalc.com> added the comment:

I closed maybe this issue too quickly. My commit doesn't solve the initial issue: Python doesn't provide a portable "wallclock" function.

wallclock.patch should be updated to use:

 - time.clock() on Windows (use QueryPerformanceCounter)
 - or time.clock_gettime(CLOCK_MONOTONIC_RAW) if available
 - or time.clock_gettime(CLOCK_MONOTONIC) if available
 - or time.time() (which is usually gettimeofday())

Pseudo-code:

wallclock = None
if hasattr(time, 'clock_gettime') and hasattr(time, 'CLOCK_MONOTONIC_RAW'):
  # I understood that CLOCK_MONOTONIC_RAW is more reliable
  # than CLOCK_MONOTONIC, because CLOCK_MONOTONIC may be adjusted
  # by NTP. I don't know if it's correct.
  def wallclock():
    return time.clock_gettime(CLOCK_MONOTONIC_RAW)

elif hasattr(time, 'clock_gettime') and hasattr(time, 'CLOCK_MONOTONIC'):
  def wallclock():
    return time.clock_gettime(CLOCK_MONOTONIC)

elif os.name == 'nt':
  # define a new function to be able to set its docstring
  def wallclock():
    return time.clock()

else:
  def wallclock():
     return time.time()
if wallclock is not None:
   wallclock.__doc__ = 'monotonic time'
else:
   del wallclock

wallclock() doc should also explain that time.time() may be adjusted by NTP or manually by the administrator.

--

By the way, it would be nice to expose the precision of time.clock(): it's 1/divisor or 1/CLOCKS_PER_SEC on Windows, 1/CLOCKS_PER_SEC on UNIX.

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resolution: fixed -> 
status: closed -> open

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue10278>
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