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datetime-RFC2822 roundtripping #37748Description
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GitHub fields:
assignee = 'https://github.com/abalkin'
closed_at = <Date 2012-08-23.04:10:12.456>
created_at = <Date 2003-01-09.18:24:53.000>
labels = ['easy', 'type-feature', 'library', 'expert-email']
title = 'datetime-RFC2822 roundtripping'
updated_at = <Date 2012-08-23.04:10:12.455>
user = 'https://github.com/doerwalter' bugs.python.org fields:
activity = <Date 2012-08-23.04:10:12.455>
actor = 'belopolsky'
assignee = 'belopolsky'
closed = True
closed_date = <Date 2012-08-23.04:10:12.456>
closer = 'belopolsky'
components = ['Library (Lib)', 'email']
creation = <Date 2003-01-09.18:24:53.000>
creator = 'doerwalter'
dependencies = ['5094']
files = ['8214', '21886', '22649', '26094', '26954', '26955']
hgrepos = []
issue_num = 665194
keywords = ['patch', 'easy']
message_count = 36.0
messages = ['53725', '53726', '53727', '53728', '53729', '53730', '53731', '53732', '53733', '81810', '107436', '135154', '135211', '135222', '135226', '135228', '140317', '140747', '140748', '161644', '163486', '163516', '163620', '168834', '168835', '168837', '168838', '168840', '168841', '168912', '168913', '168914', '168916', '168919', '168920', '168922']
nosy_count = 10.0
nosy_names = ['tim.peters', 'barry', 'akuchling', 'doerwalter', 'belopolsky', 'ajaksu2', 'eric.araujo', 'r.david.murray', 'Alexander.Belopolsky', 'python-dev']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue665194'
versions = ['Python 3.3'] Activitydoerwalter commented on Jan 9, 2003 ContributorAuthor More actions It would be good to have a simply way to convert
between datetime objects and RFC2822 style strings.
From string to datetime is easy with
datetime.datetime(*email.Utils.parsedate(m)[:7]) (but
this drops the timezone), but the other direction seems
impossible. email.Utils.formatdate takes a timestamp
argument, but AFAICT there's no way to get a timestamp
out of a datetime object.
Of course the best solution (ignoring backwards
compatibility) would be for parsedate und formatdate to
return/accept datetime objects or for datetime to have
the appropriate methods. tim-one commented on Jan 11, 2003 Logged In: YES
user_id=31435
You can get a timestamp like so:
>>> time.mktime(datetime.date(2002, 1, 1).timetuple())
1009861200.0
>>> The dates for which this works depends on the platform
mktime implementation, though.
BTW, this sounds a lot more like a new feature request
than a bug! doerwalter commented on Jan 11, 2003 ContributorAuthor More actions Logged In: YES
user_id=89016
OK, I'll mark this a feature request.
datetime has fromordinal() and toordinal(), it has
fromtimestamp(), so I'd say a totimestamp() method would be
a logical addition. tim-one commented on Jan 11, 2003 Logged In: YES
user_id=31435
Define what totimestamp() should do. The range of
timestamps supported by the *platform* C library (and so
indirectly by Python's time module) isn't defined by any
standard, and isn't easily discoverable either. It may or
may not work before 1970, may or may not after 2038.
datetime covers days far outside that range. Note that
even a double doesn't have enough bits of precision to
cover the full range of datetime values, either.
In contrast, ordinals are wholly under Python's control, so
we can promise surprise-free conversion in both directions.
All we can promise about timestamps is that if the platform
supports a timestamp for a time in datetime's range,
datetime can make sense of it. doerwalter commented on Jan 13, 2003 ContributorAuthor More actions Logged In: YES
user_id=89016
totimestamp() should be the inverse of fromtimestamp(), i.e.
foo.totimestamp() should be the same as
time.mktime(foo.timetuple()).
datetime.datetime.totimestamp() should raise OverflowError
iff time.mktime() raises OverflowError.
But as this may lose precision, I'd say it would be better,
if datetime supported RFC1123 conversion directly, i.e. two
methods frommime() and tomime(), that parse and format
strings like "Sun, 06 Nov 1994 08:49:37 GMT" (what
rfc822.parsedate() and rfc822.formatdate() do) brettcannon commented on May 23, 2003 Logged In: YES
user_id=357491
time.strptime doesn't solve your problem? doerwalter commented on May 26, 2003 ContributorAuthor More actions Logged In: YES
user_id=89016
time.strptime() is locale aware, but RFC1123 & RFC822
require english day and month names, so time.strptime()
can't be used as-is. (And of course time.strptime() only
works for formatting, not for parsing) akuchling commented on Dec 21, 2006 Moving to feature requests. doerwalter commented on Mar 7, 2007 ContributorAuthor More actions Here is a patch that implements to formatting part. It adds a method mimeformat() to the datetime class. The datetime object must have a tzinfo for this to work.
File Added: datetime-mimeformat.diff devdanzin commented on Feb 12, 2009 Patch includes tests, should be updated. abalkin commented on Aug 22, 2012
So since the other tests were passing before, presumably there
is some test that could be added to exercise the bug you were
fixing. Do you remember what that was?
Yes, the issue was the one that was mentioned in an XXX comment: in many places UTC offset was different at different historical times but standard C library and Python's time module provides a single constant for it. There are plenty of examples that can be found in Olson's database (Europe/Kiev comes to mind), but it is not easy to devise a test that will work cross-platform. Maybe we should just restrict the test to Linux/BSD family of OSes? bitdancer commented on Aug 23, 2012 I think restricting the test is fine. If we find a platform-specific bug on another platform we can add a test specific to that platform when we fix the bug.
Can you provide the test? I'm going to commit what I've got at this point to make sure I don't miss the RC. AlexanderBelopolsky commented on Aug 23, 2012 AlexanderBelopolskymannequin Please commit. I'll add the test.
On Wed, Aug 22, 2012 at 9:11 PM, R. David Murray <[email protected]> wrote:
R. David Murray added the comment:
I think restricting the test is fine. If we find a platform-specific bug on another platform we can add a test specific to that platform when we fix the bug.
Can you provide the test? I'm going to commit what I've got at this point to make sure I don't miss the RC.
----------
Python tracker <[email protected]>
<http://bugs.python.org/issue665194\>
python-dev commented on Aug 23, 2012 bitdancer commented on Aug 23, 2012 Leaving open until the test is committed. python-dev commented on Aug 23, 2012 python-dev commented on Aug 23, 2012 python-dev commented on Aug 23, 2012
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