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Python 3.3 has 4 new functions to set the access and modification time of a file (only os.utime() was already present in Python 3.2). New functions taking timestamp with a nanonsecond resolution use a tuple of int because the float type doesn't support nanosecond resolution. Thanks to the PEP 410, we can simplify the API to use a simple number (int, float or Decimal) instead of a tuple of 2 integers.
Current API:
- futimes(fd[, (atime, mtime)]): 1 argument for timestamps
- lutimes(path[, (atime, mtime)]): 1 argument for timestamps
- utime(path[, (atime, mtime)]): 1 argument for timestamps
- futimens(fd[, (atime_sec, atime_nsec), (mtime_sec, mtime_nsec)]): 2 arguments for timestamps
- utimensat(dirfd, path[, atime=(atime_sec, atime_nsec), mtime=(mtime_sec, mtime_nsec), flags=0]): 2 arguments for timestamps
I propose to:
- support Decimal type in all functions: avoid conversion to float to not lose precision
- remove os.futimens(): os.futimes() does already use futimens() if the function is present (and Decimal can be used to get nanosecond resolution)
- change os.utimensat() API to: os.utimensat(dirfd, path[, (atime, mtime), flags=0])

New changeset d297f9b10c64 by Victor Stinner in branch 'default':
Issue #13964: Write tests for new os.*utime*() functions
http://hg.python.org/cpython/rev/d297f9b10c64 

> Current API:
Oh, I forgot:
- futimesat(dirfd, path[, (atime, mtime)])
This API looks fine.

New changeset c6e9c4d18b36 by Victor Stinner in branch 'default':
Issue #13964: Test also os.futimesat()
http://hg.python.org/cpython/rev/c6e9c4d18b36 

I suggest to support the following functions:
futimes(fd, (atime, mtime), flags=0)
utimes(path, (atime, mtime), flags=0)
utimesat(dirfd, path, (atime, mtime), flags=0)
And deprecate other functions already present in 3.2.
flags argument of utimes*() would specify e.g. if symlinks should be dereferenced, so lutime*() wouldn't be needed.

New changeset 478fb4869c99 by Victor Stinner in branch 'default':
Issue #13964: Split os.*utime*() subsecond tests into multiple tests to help
http://hg.python.org/cpython/rev/478fb4869c99 

New changeset 58bd6a58365d by Victor Stinner in branch 'default':
Issue #13964: Skip os.*utime*() tests if os.stat() doesn't support timestamp
http://hg.python.org/cpython/rev/58bd6a58365d 

> New changeset 478fb4869c99 by Victor Stinner in branch 'default':
> Issue #13964: Split os.*utime*() subsecond tests into multiple tests...
Oops, I also commited my change on extract_time() by mistake. But it is not completly a mistake: it was the goal of my patch serie :-)
This commit changes two things on extract_time().
 - always use nanoseconds: if we need microseconds, divide by 1000
 - use (long)(fmod()*1e9) to get nanoseconds instead of the previous code, I'm not sure that this change is correct

signal.sigtimedwait() API should also be changed from:
 sigtimedwait(sigset, (timeout_sec, timeout_nsec))
to:
 sigtimedwait(sigset, timeout)
where timeout can be an int, float or decimal.Decimal. The function was introduced in Python 3.3, so its API can be changed.

Updated version of my suggestion:
os.futime(fd, (atime, mtime))
os.utime(path, (atime, mtime), flags=0)
os.utimeat(dirfd, path, (atime, mtime), flags=0)
atime and mtime could be int, float, decimal.Decimal or None.
All other os.*utime*() functions were introduced in 3.3, so they would be removed.
flags argument of os.utime() and os.utimeat() could be 0 or os.SYMLINK_NOFOLLOW.

Here is a first step: add _PyTime_ObjectToTimespec() to pytime.h and use it for signal.sigtimedwait().
signal.sigtimedwait(sigwait, (timeout_sec, timeout_nsec)) becomes signal.sigtimedwait(sigwait, timeout).
I chose pytime.h instead of timefuncs.h because I plan to use _PyTime_ObjectToTimespec() in the posix module. I don't want to have a copy of this function in each module: timefuncs.h requires to compile the module with _time.c.

New changeset 67d9595a833c by Victor Stinner in branch 'default':
Issue #13964: signal.sigtimedwait() timeout is now a float instead of a tuple
http://hg.python.org/cpython/rev/67d9595a833c 

I created the issue #14180 to prepare a refactoring before changing os.*utime*() functions.

Um, doesn't the rejection of PEP 410 mean this should be discontinued?

> Um, doesn't the rejection of PEP 410 mean this should be discontinued?
There is an issue in shutil.copystat() on copying the timestamp: in this specific use case, we need nanosecond resolution.
Guido proposes (in a private mail thread) to add st_atime_ns, st_mtime_ns, st_ctime_ns fields to os.stat() and make os.*utime*() functions accept a (sec, nsec) tuple. It would still be possible to pass a number or seconds as an int or float.
I plan to implement this request.

utime.patch: ugly draft to add support of (sec, nsec) tuple to os.*utime*() functions.

After Guido rejected 410 and said "let's just do nanoseconds, take it to the bug tracker" I created issue #14127. Your having changed this issue to be the same thing means that at least one of 'em is redundant. Could you engage on that issue, or close it, or something?

I just asked Guido in person, and he says he never intended to suggest accepting a (sec, nsec) tuple. os.*utime* may accept atime and mtime as either float seconds-since-the-epoch, or int nanoseconds-since-the-epoch when passed in using the ns= named parameter.

This issue is a duplicate of #14127.