[Python-Dev] iso8601 parsing

Chris Barker chris.barker at noaa.gov
Wed Oct 25 19:45:32 EDT 2017

On Wed, Oct 25, 2017 at 4:22 PM, Alexander Belopolsky <
alexander.belopolsky at gmail.com> wrote:

> > times. The only difference is that instead of calling the type directly,
> > you call the appropriate classmethod.
> >
> > What am I missing?
> Nothing. The only annoyance is that the data processing code typically
> needs to know the type anyway, so the classmethod is one more variable
> to keep track of.

I don't think anyone is arguing that is is hard to do either way, or that
hard to use either way.

I think it comes down to a trade-off between:

Having an API for datetime that is like the datetime for number types:

 int(str(an_int)) == an_int


 datetime(str(a_datetime)) == a_datetime

Alexander strongly supports that.

Or an API that is perhaps more like the rest of the datetime api, which has
a number of alternate constructors:




And has:


So a


would make a lot of sense.

I would note that the number types don't have all those alternate
constructors Also, the number types mostly have a single parameter (except
int has an optional base parameter). So I'm not sure the parallel is that

Would it be horrible if we did both?

After all, right now, datetime has:

In [16]: dt.isoformat()
Out[16]: '2017-10-25T16:30:48.744489'

In [18]: dt.__str__()
Out[18]: '2017-10-25 16:30:48.744489'

which do almost the same thing (I understand the "T" is option in iso 8601)

However, maybe they are different when you add a time zone?

ISO 8601 support offsets, but not time zones -- presumably the __str__
supports the full datetime tzinfo somehow. Which may be why .isoformat()

Though I don't think that means you couldn't have the __init__ parse proper
ISO strings, in addition to the full datetime __str__ results.



Christopher Barker, Ph.D.

Emergency Response Division
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Chris.Barker at noaa.gov
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