[issue15443] datetime module has no support for nanoseconds

[Marc-Andre Lemburg]

Marc-Andre Lemburg <mal at egenix.com> added the comment:

Marc-Andre Lemburg wrote:
> 
>> Alexander Belopolsky <alexander.belopolsky at gmail.com> added the comment:
>>
>> On Wed, Jul 25, 2012 at 4:17 AM, Marc-Andre Lemburg <report at bugs.python.org> wrote:
>>> ... full C double precision for the time part of a timestamp,
>>> which covers nanoseconds just fine.
>>
>> No, it does not:
>>
>>>>> import time
>>>>> t = time.time()
>>>>> t + 5e-9 == t
>> True
>>
>> In fact, C double precision is barely enough to cover microseconds:
>>
>>>>> t + 1e-6 == t
>> False
>>
>>>>> t + 1e-7 == t
>> True
> 
> I was referring to the use of a C double to store the time part
> in mxDateTime. mxDateTime uses the C double to store the number of
> seconds since midnight, so you don't run into the Unix ticks value
> range problem you showcased above.

There's enough room to even store 1/100th of a nanosecond, which may
be needed for some physics experiments :-)

False
>>> x == x + 1e-10
False
>>> x == x + 1e-11
False
>>> x == x + 1e-12
True

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue15443>
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