timestamp() method for datetime objects

[catlee]

BPO	1457227
Nosy	@gvanrossum, @catlee
Files	datetime.patch: datetime.patch

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

Show more details

GitHub fields:

assignee = None
closed_at = <Date 2006-09-16.19:43:28.000>
created_at = <Date 2006-03-23.20:06:07.000>
labels = ['extension-modules']
title = 'timestamp() method for datetime objects'
updated_at = <Date 2006-09-16.19:43:28.000>
user = 'https://github.com/catlee'

bugs.python.org fields:

activity = <Date 2006-09-16.19:43:28.000>
actor = 'davidfraser'
assignee = 'none'
closed = True
closed_date = None
closer = None
components = ['Extension Modules']
creation = <Date 2006-03-23.20:06:07.000>
creator = 'catlee'
dependencies = []
files = ['7097']
hgrepos = []
issue_num = 1457227
keywords = ['patch']
message_count = 5.0
messages = ['49841', '49842', '49843', '49844', '49845']
nosy_count = 3.0
nosy_names = ['gvanrossum', 'davidfraser', 'catlee']
pr_nums = []
priority = 'normal'
resolution = 'rejected'
stage = None
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue1457227'
versions = []

[catlee]

This patch adds a timestamp() method to datetime
objects. It is equivalent to:
time.mktime(self.timetuple())

I pulled out the dstflag calculation code from
datetime_timetuple into a new function, get_dstflag, so
that datetime_timestamp can make use of the same code.

The patch also includes updates to the datetime
documentation, and a simple unit test.

[gvanrossum]

Logged In: YES
user_id=6380

I'm against this functionality.

It suggests an linkage between the "naive"
(timezone-unaware) time carried in the datetime object, and
the UTC space that posix timestamps represent. The entire
point of the datetime type (unless an explicit tzinfo is
passed) is that it doesn't know which timezone it represents.

When you call time.mktime(self.timetuple()), you as the
application make the determination that the timetuple (which
is still tz-unaware!) represents your current local time.
That's a fine decision for the app to make. But I don't
think users should be lured into believing there's an
equivalency inherent in the datetime type -- there isn't.

[catlee]

Logged In: YES
user_id=186532

The .fromtimestamp and .utcfromtimestamp class methods
already imply this linkage, don't they?

What if timestamp() only works if the datetime object isn't
"naive"?

[gvanrossum]

Logged In: YES
user_id=6380

Well, that they both exist implies that the linkage is
ambiguous...

I think it's just not worth the new API given that it's (as
you admit) just a shorthand for two other calls.

There's also the problem that the range for timestamps is
much smaller than the range of datetime -- this isn't a
problem for .[utc]fromtimestamp() but is a problem for the
reverse API.

[davidfraser]

Logged In: YES
user_id=221678

I know this is closed...
I think it would be helpful to either

1. add a description to the documentation of how to convert
   back, explaining the timezone story
2. add a timestamp() function that takes a timezone parameter