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bpo-43407: Clarify comparisons of time.monotonic() et al results (GH-24757)

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Previous wording implied that only the result of call N and N+1 could be
meaningfully compared, whereas comparing call N and N+M is fine.
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Alex Willmer 2021-03-06 01:22:13 +00:00 • committed by GitHub
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2 changed files with 8 additions and 4 deletions
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8
Doc/library/time.rst
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@ -277,7 +277,7 @@ Functions
Return the value (in fractional seconds) of a monotonic clock, i.e. a clock Return the value (in fractional seconds) of a monotonic clock, i.e. a clock
that cannot go backwards. The clock is not affected by system clock updates. that cannot go backwards. The clock is not affected by system clock updates.
The reference point of the returned value is undefined, so that only the The reference point of the returned value is undefined, so that only the
difference between the results of consecutive calls is valid. difference between the results of two calls is valid.
Use :func:`monotonic_ns` to avoid the precision loss caused by the Use :func:`monotonic_ns` to avoid the precision loss caused by the
:class:`float` type. :class:`float` type.
@ -306,7 +306,7 @@ Functions
clock with the highest available resolution to measure a short duration. It clock with the highest available resolution to measure a short duration. It
does include time elapsed during sleep and is system-wide. The reference does include time elapsed during sleep and is system-wide. The reference
point of the returned value is undefined, so that only the difference between point of the returned value is undefined, so that only the difference between
the results of consecutive calls is valid. the results of two calls is valid.
Use :func:`perf_counter_ns` to avoid the precision loss caused by the Use :func:`perf_counter_ns` to avoid the precision loss caused by the
:class:`float` type. :class:`float` type.
@ -334,7 +334,7 @@ Functions
CPU time of the current process. It does not include time elapsed during CPU time of the current process. It does not include time elapsed during
sleep. It is process-wide by definition. The reference point of the sleep. It is process-wide by definition. The reference point of the
returned value is undefined, so that only the difference between the results returned value is undefined, so that only the difference between the results
of consecutive calls is valid. of two calls is valid.
Use :func:`process_time_ns` to avoid the precision loss caused by the Use :func:`process_time_ns` to avoid the precision loss caused by the
:class:`float` type. :class:`float` type.
@ -626,7 +626,7 @@ Functions
CPU time of the current thread. It does not include time elapsed during CPU time of the current thread. It does not include time elapsed during
sleep. It is thread-specific by definition. The reference point of the sleep. It is thread-specific by definition. The reference point of the
returned value is undefined, so that only the difference between the results returned value is undefined, so that only the difference between the results
of consecutive calls in the same thread is valid. of two calls in the same thread is valid.
Use :func:`thread_time_ns` to avoid the precision loss caused by the Use :func:`thread_time_ns` to avoid the precision loss caused by the
:class:`float` type. :class:`float` type.

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Misc/NEWS.d/next/Documentation/2021-03-04-22-53-03.bpo-43407.x570l5.rst Normal file
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@ -0,0 +1,4 @@
Clarified that a result from :func:`time.monotonic`,
:func:`time.perf_counter`, :func:`time.process_time`, or
:func:`time.thread_time` can be compared with the result from any following
call to the same function - not just the next immediate call.