(Originally posted at http://bugs.python.org/issue25428)
Proposal: Functions in `datetime` which take a `tzinfo` object should
allow, as an alternative, a numerical argument, which would be
interpreted as the number of hours. There are time zones with
half-hour offsets, so floats should be allowed.
Current: To create a `datetime` object with a particular time zone offset,
from datetime import datetime, timezone, timedelta
mytime = datetime(2015, 10, 16, 9, 13, 0,
tzinfo=timezone(timedelta(hours=-7)))
That's two extra imports and two extra objects created.
Suggested way:
mytime = datetime(2015, 10, 16, 9, 13, 0, tzinfo=-7)
# mytime.tzinfo == -7
# or: mytime.tzinfo == timezone(timedelta(-7))
Alternatively, introduce a new keyword parameter to explictily indicate hours:
mytime = datetime(2015, 10, 16, 9, 13, 0, tzhours=-7)
# mytime.tzinfo == timezone(timedelta(-7))
Rationale:
For time zones, hours are the normal unit of time. At least, I think
about time zones in hours, and I don't know who would think about them
in minutes.
Imagine you have about a year of experience dabbling in Python, and
you're trying to do a relatively simple task, like reading PDT times
and converting them to local time. You would go to the datetime docs,
and see that you need to pass in a tzinfo object. You look up
`tzinfo`:
"""tzinfo is an abstract base class, meaning that this class should
not be instantiated directly. You need to derive a concrete subclass,
and (at least) supply implementations of the standard tzinfo methods
needed by the datetime methods you use."""
Well, great. If you want to convert times, you'll have to subclass an
abstract base class (if you know what that means), and implement five
methods. You'd probably have to read the whole docs for this ABC, too.
(The docs for `tzinfo` are nine pages long on my screen.)
If you're not frightened off by the first two sentences, you'll see
that there's the concrete subclass `datetime.timezone`. We're two
levels down, now. Going there, you'll see that you need to pass in a
`datetime.timedelta` object. Three levels. You need to learn three
classes to specify an hour offset: `tzinfo`, `timezone`, and
`timedelta`.
Time zones are something that many non-programmers understand, and the
rules are pretty simple (except for DST). Ideally, it should be simple
to do simple things.
PS: There seems to be an unnecessary naming inconsistency with
`.astimezone`, `fromtimestamp`, and `now` taking a `tz` kwarg rather
than a `tzinfo` kwarg.
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