From d2d521eafdea651de075f987ca80bece033b9b40 Mon Sep 17 00:00:00 2001 From: R David Murray Date: Fri, 25 May 2012 23:22:59 -0400 Subject: #665194: Add a localtime function to email.utils. Without this function people would be tempted to use the other date functions in email.utils to compute an aware localtime, and those functions are not as good for that purpose as this code. The code is Alexander Belopolsy's from his proposed patch for issue 9527, with a fix (and additional tests) by Brian K. Jones. --- Doc/library/email.util.rst | 18 ++++++++-- Lib/email/utils.py | 53 ++++++++++++++++++++++++++++ Lib/test/test_email/test_utils.py | 73 +++++++++++++++++++++++++++++++++++++++ Misc/ACKS | 1 + Misc/NEWS | 3 ++ 5 files changed, 146 insertions(+), 2 deletions(-) diff --git a/Doc/library/email.util.rst b/Doc/library/email.util.rst index 2f9ef89..1383104 100644 --- a/Doc/library/email.util.rst +++ b/Doc/library/email.util.rst @@ -93,8 +93,6 @@ There are several useful utilities provided in the :mod:`email.utils` module: corresponding a :class:`~datetime.timezone` :class:`~datetime.tzinfo`. .. versionadded:: 3.3 - - .. function:: mktime_tz(tuple) Turn a 10-tuple as returned by :func:`parsedate_tz` into a UTC timestamp. It @@ -140,6 +138,22 @@ There are several useful utilities provided in the :mod:`email.utils` module: .. versionadded:: 3.3 +.. function:: localtime(dt=None) + + Return local time as an aware datetime object. If called without + arguments, return current time. Otherwise *dt* argument should be a + :class:`~datetime.datetime` instance, and it is converted to the local time + zone according to the system time zone database. If *dt* is naive (that + is, ``dt.tzinfo`` is ``None``), it is assumed to be in local time. In this + case, a positive or zero value for *isdst* causes ``localtime`` to presume + initially that summer time (for example, Daylight Saving Time) is or is not + (respectively) in effect for the specified time. A negative value for + *isdst* causes the ``localtime`` to attempt to divine whether summer time + is in effect for the specified time. + + .. versionadded:: 3.3 + + .. function:: make_msgid(idstring=None, domain=None) Returns a string suitable for an :rfc:`2822`\ -compliant diff --git a/Lib/email/utils.py b/Lib/email/utils.py index b7e1bb9..39f7903 100644 --- a/Lib/email/utils.py +++ b/Lib/email/utils.py @@ -363,3 +363,56 @@ def collapse_rfc2231_value(value, errors='replace', except LookupError: # charset is not a known codec. return unquote(text) + + +# +# datetime doesn't provide a localtime function yet, so provide one. Code +# adapted from the patch in issue 9527. This may not be perfect, but it is +# better than not having it. +# + +def localtime(dt=None, isdst=-1): + """Return local time as an aware datetime object. + + If called without arguments, return current time. Otherwise *dt* + argument should be a datetime instance, and it is converted to the + local time zone according to the system time zone database. If *dt* is + naive (that is, dt.tzinfo is None), it is assumed to be in local time. + In this case, a positive or zero value for *isdst* causes localtime to + presume initially that summer time (for example, Daylight Saving Time) + is or is not (respectively) in effect for the specified time. A + negative value for *isdst* causes the localtime() function to attempt + to divine whether summer time is in effect for the specified time. + + """ + if dt is None: + seconds = time.time() + else: + if dt.tzinfo is None: + # A naive datetime is given. Convert to a (localtime) + # timetuple and pass to system mktime together with + # the isdst hint. System mktime will return seconds + # sysce epoch. + tm = dt.timetuple()[:-1] + (isdst,) + seconds = time.mktime(tm) + else: + # An aware datetime is given. Use aware datetime + # arithmetics to find seconds since epoch. + delta = dt - datetime.datetime(1970, 1, 1, + tzinfo=datetime.timezone.utc) + seconds = delta.total_seconds() + tm = time.localtime(seconds) + + # XXX: The following logic may not work correctly if UTC + # offset has changed since time provided in dt. This will be + # corrected in C implementation for platforms that support + # tm_gmtoff. + if time.daylight and tm.tm_isdst: + offset = time.altzone + tzname = time.tzname[1] + else: + offset = time.timezone + tzname = time.tzname[0] + + tz = datetime.timezone(datetime.timedelta(seconds=-offset), tzname) + return datetime.datetime.fromtimestamp(seconds, tz) diff --git a/Lib/test/test_email/test_utils.py b/Lib/test/test_email/test_utils.py index e003a64..d9c4d70 100644 --- a/Lib/test/test_email/test_utils.py +++ b/Lib/test/test_email/test_utils.py @@ -1,5 +1,7 @@ import datetime from email import utils +import test.support +import time import unittest class DateTimeTests(unittest.TestCase): @@ -43,3 +45,74 @@ class DateTimeTests(unittest.TestCase): self.assertEqual( utils.parsedate_to_datetime(self.datestring + ' -0000'), self.naive_dt) + + +class LocaltimeTests(unittest.TestCase): + + def test_localtime_is_tz_aware_daylight_true(self): + test.support.patch(self, time, 'daylight', True) + t = utils.localtime() + self.assertIsNot(t.tzinfo, None) + + def test_localtime_is_tz_aware_daylight_false(self): + test.support.patch(self, time, 'daylight', False) + t = utils.localtime() + self.assertIsNot(t.tzinfo, None) + + def test_localtime_daylight_true_dst_false(self): + test.support.patch(self, time, 'daylight', True) + t0 = datetime.datetime(2012, 3, 12, 1, 1) + t1 = utils.localtime(t0, isdst=-1) + t2 = utils.localtime(t1) + self.assertEqual(t1, t2) + + def test_localtime_daylight_false_dst_false(self): + test.support.patch(self, time, 'daylight', False) + t0 = datetime.datetime(2012, 3, 12, 1, 1) + t1 = utils.localtime(t0, isdst=-1) + t2 = utils.localtime(t1) + self.assertEqual(t1, t2) + + def test_localtime_daylight_true_dst_true(self): + test.support.patch(self, time, 'daylight', True) + t0 = datetime.datetime(2012, 3, 12, 1, 1) + t1 = utils.localtime(t0, isdst=1) + t2 = utils.localtime(t1) + self.assertEqual(t1, t2) + + def test_localtime_daylight_false_dst_true(self): + test.support.patch(self, time, 'daylight', False) + t0 = datetime.datetime(2012, 3, 12, 1, 1) + t1 = utils.localtime(t0, isdst=1) + t2 = utils.localtime(t1) + self.assertEqual(t1, t2) + + def test_localtime_epoch_utc_daylight_true(self): + test.support.patch(self, time, 'daylight', True) + t0 = datetime.datetime(1970, 1, 1, tzinfo = datetime.timezone.utc) + t1 = utils.localtime(t0) + self.assertEqual(t0, t1) + + def test_localtime_epoch_utc_daylight_false(self): + test.support.patch(self, time, 'daylight', False) + t0 = datetime.datetime(1970, 1, 1, tzinfo = datetime.timezone.utc) + t1 = utils.localtime(t0) + self.assertEqual(t0, t1) + + def test_localtime_epoch_notz_daylight_true(self): + test.support.patch(self, time, 'daylight', True) + t0 = datetime.datetime(1970, 1, 1) + t1 = utils.localtime(t0) + t2 = utils.localtime(t0.replace(tzinfo=None)) + self.assertEqual(t1, t2) + + def test_localtime_epoch_notz_daylight_false(self): + test.support.patch(self, time, 'daylight', False) + t0 = datetime.datetime(1970, 1, 1) + t1 = utils.localtime(t0) + t2 = utils.localtime(t0.replace(tzinfo=None)) + self.assertEqual(t1, t2) + + +if __name__ == '__main__': + unittest.main() diff --git a/Misc/ACKS b/Misc/ACKS index 265cb17..16f55ea 100644 --- a/Misc/ACKS +++ b/Misc/ACKS @@ -506,6 +506,7 @@ Simon Johnston Matt Joiner Thomas Jollans Nicolas Joly +Brian K. Jones Evan Jones Jeremy Jones Richard Jones diff --git a/Misc/NEWS b/Misc/NEWS index 369b1a5..4f20446 100644 --- a/Misc/NEWS +++ b/Misc/NEWS @@ -46,6 +46,9 @@ Core and Builtins Library ------- +- Issue #665194: Added a localtime function to email.utils to provide an + aware local datetime for use in setting Date headers. + - Issue #12586: Added new provisional policies that implement convenient unicode support for email headers. See What's New for details. -- cgit v0.12