[Python-Dev] Issue 2736: datetimes and Unix timestamps (original) (raw)

Guido van Rossum guido at python.org
Tue Jun 5 20:19:53 CEST 2012

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)

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