arrow-py
Support for 9 fractional second digits (ns)
Firstly, 9 fractional second digits is approved in ISO8610(RFC3339).
... one or more digits representing a decimal fraction of a second
as it put (https://www.w3.org/TR/NOTE-datetime).
A 9 fractional second digits ISO8610 datetime can be generated in a Linux/Unix environment(not OS X) as this way:
$ date --rfc-3339=ns
2016-06-23 16:40:27.329428631+08:00
I'm using Arrow 0.7.0, with python 2.7.11, on both OS X(10.11.5) and Ubuntu 14.04.
As for Arrow implementation in my environments:
>>> import arrow
>>> s1='2016-06-23 16:40:27.329428631+08:00'
>>> arrow.get(s1)
Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/lib/python2.7/site-packages/arrow/arrow.py", line 286, in __repr__ return '<{0} [{1}]>'.format(self.__class__.__name__, self.__str__()) File "/usr/lib/python2.7/site-packages/arrow/arrow.py", line 289, in __str__ return self._datetime.isoformat() ValueError: tzinfo.utcoffset() returned 1440; must be in -1439 .. 1439
But works fine in case of 6 fractional second digits:
>>> import arrow
>>> s2='2016-06-23 16:40:27.329428+08:00'
>>> arrow.get(s2)
<Arrow [2016-06-24T16:40:27.329428+08:00]>
Lastly, I have a quick look in parse.py, the reason of the above seems to be Arrow never support a 9 fractional second digits datetime string, and only support up to 6 digits (the _FORMAT_RE in https://github.com/crsmithdev/arrow/blob/master/arrow/parser.py line 17).
Update: I have noticed that datetime itself do not support 9 fractional second digits either (https://docs.python.org/2/library/datetime.html#datetime.datetime.microsecond ):
datetime.microsecond In range(1000000).
Confirmed, but not having it in datetime itself makes fixing it more involved.
This is the current situation. Arrow will now parse this timestamp but truncate it to 6 fractional seconds.
Python 2.7.12 (default, Nov 12 2018, 14:36:49)
[GCC 5.4.0 20160609] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import arrow
>>> s1='2016-06-23 16:40:27.329428631+08:00'
>>> arrow.get(s1)
<Arrow [2016-06-23T16:40:27.329429+08:00]>
Addressing https://github.com/crsmithdev/arrow/issues/636 should help with rounding large subseconds, but like people have said previously, without official ns support from datetime, the change to support ns will be more involved.
