[Python-Dev] Issue 2736: datetimes and Unix timestamps

[Guido van Rossum]

On Tue, Jun 5, 2012 at 11:14 AM, Alexander Belopolsky
<alexander.belopolsky at gmail.com> wrote:
> On Tue, Jun 5, 2012 at 1:41 PM, Guido van Rossum <guido at python.org> wrote:
>> What do they want to set the dst flag for?
>
> To shift the responsibility to deal with the DST ambiguity to the
> user.   This is what POSIX mktime with varying degree of success.
>
>> I think I am advocating for the former but without the dst flag.
>
> The cost of dst flag is low and most users will ignore it anyways, but
> by providing it we will at least acknowledge the issue.  I don't care
> much one way or another.

Me neither, TBH. Although if we ever get that "local time" tzinfo
object, we may regret it. So I propose to launch without it and see if
people object. There simply isn't a way to roundtrip for times that
fall in the DST->std transition, and I doubt that many users will want
to think about it (they'd have to store an extra bit with all their
datetime objects -- it would be better to get them to use tzinfo
objects instead...).

> The remaining issue is the return type.  Most of the use cases that
> have been brought up cast the timestamp to int as soon as it is
> computed.   I recall a recent discussion about high-presision
> timestamps, but don't recall the conclusion.  I guess we should offer
> timestamp() returning float and let those who care about range or
> precision write their own solution.

Python uses floats pretty much everywhere for posix timestamps. So let
it return a float.

-- 
--Guido van Rossum (python.org/~guido)