Issue #10827: Changed the rules for 2-digit years. The time.asctime
function will now format any year when time.accept2dyear is false and will accept years >= 1000 otherwise. The year range accepted by time.mktime and time.strftime is still system dependent, but time.mktime will now accept full range supported by the OS. Conversion of 2-digit years to 4-digit is deprecated.
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@ -24,9 +24,9 @@ An explanation of some terminology and conventions is in order.
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.. index:: single: Year 2038
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* The functions in this module do not handle dates and times before the epoch or
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* The functions in this module may not handle dates and times before the epoch or
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far in the future. The cut-off point in the future is determined by the C
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library; for Unix, it is typically in 2038.
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library; for 32-bit systems, it is typically in 2038.
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.. index::
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single: Year 2000
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@ -34,20 +34,31 @@ An explanation of some terminology and conventions is in order.
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.. _time-y2kissues:
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* **Year 2000 (Y2K) issues**: Python depends on the platform's C library, which
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* **Year 2000 (Y2K) issues**: Python depends on the platform's C library, which
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generally doesn't have year 2000 issues, since all dates and times are
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represented internally as seconds since the epoch. Functions accepting a
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:class:`struct_time` (see below) generally require a 4-digit year. For backward
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compatibility, 2-digit years are supported if the module variable
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``accept2dyear`` is a non-zero integer; this variable is initialized to ``1``
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unless the environment variable :envvar:`PYTHONY2K` is set to a non-empty
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string, in which case it is initialized to ``0``. Thus, you can set
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:envvar:`PYTHONY2K` to a non-empty string in the environment to require 4-digit
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years for all year input. When 2-digit years are accepted, they are converted
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according to the POSIX or X/Open standard: values 69-99 are mapped to 1969-1999,
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and values 0--68 are mapped to 2000--2068. Values 100--1899 are always illegal.
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Note that this is new as of Python 1.5.2(a2); earlier versions, up to Python
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1.5.1 and 1.5.2a1, would add 1900 to year values below 1900.
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represented internally as seconds since the epoch. Function :func:`strptime`
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can parse 2-digit years when given ``%y`` format code. When 2-digit years are
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parsed, they are converted according to the POSIX and ISO C standards: values
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69--99 are mapped to 1969--1999, and values 0--68 are mapped to 2000--2068.
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For backward compatibility, years with less than 4 digits are treated
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specially by :func:`asctime`, :func:`mktime`, and :func:`strftime` functions
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that operate on a 9-tuple or :class:`struct_time` values. If year (the first
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value in the 9-tuple) is specified with less than 4 digits, its interpretation
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depends on the value of ``accept2dyear`` variable.
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If ``accept2dyear`` is true (default), a backward compatibility behavior is
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invoked as follows:
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- for 2-digit year, century is guessed according to POSIX rules for
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``%y`` strptime format. A deprecation warning is issued when century
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information is guessed in this way.
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- for 3-digit or negative year, a :exc:`ValueError` exception is raised.
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If ``accept2dyear`` is false (set by the program or as a result of a
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non-empty value assigned to ``PYTHONY2K`` environment variable) all year
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values are interpreted as given.
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.. index::
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single: UTC
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@ -3,6 +3,7 @@ import time
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import unittest
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import locale
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import sysconfig
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import warnings
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class TimeTestCase(unittest.TestCase):
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@ -19,10 +20,10 @@ class TimeTestCase(unittest.TestCase):
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time.clock()
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def test_conversions(self):
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self.assertTrue(time.ctime(self.t)
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== time.asctime(time.localtime(self.t)))
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self.assertTrue(int(time.mktime(time.localtime(self.t)))
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== int(self.t))
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self.assertEqual(time.ctime(self.t),
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time.asctime(time.localtime(self.t)))
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self.assertEqual(int(time.mktime(time.localtime(self.t))),
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int(self.t))
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def test_sleep(self):
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time.sleep(1.2)
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@ -44,7 +45,7 @@ class TimeTestCase(unittest.TestCase):
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# Check year [1900, max(int)]
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self.assertRaises(ValueError, func,
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(1899, 1, 1, 0, 0, 0, 0, 1, -1))
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(999, 1, 1, 0, 0, 0, 0, 1, -1))
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if time.accept2dyear:
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self.assertRaises(ValueError, func,
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(-1, 1, 1, 0, 0, 0, 0, 1, -1))
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@ -97,7 +98,8 @@ class TimeTestCase(unittest.TestCase):
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# No test for daylight savings since strftime() does not change output
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# based on its value.
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expected = "2000 01 01 00 00 00 1 001"
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result = time.strftime("%Y %m %d %H %M %S %w %j", (0,)*9)
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with support.check_warnings():
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result = time.strftime("%Y %m %d %H %M %S %w %j", (0,)*9)
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self.assertEqual(expected, result)
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def test_strptime(self):
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@ -141,14 +143,15 @@ class TimeTestCase(unittest.TestCase):
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self.assertEqual(time.ctime(t), 'Sun Sep 16 01:03:52 1973')
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t = time.mktime((2000, 1, 1, 0, 0, 0, 0, 0, -1))
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self.assertEqual(time.ctime(t), 'Sat Jan 1 00:00:00 2000')
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try:
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bigval = time.mktime((10000, 1, 10) + (0,)*6)
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except (ValueError, OverflowError):
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# If mktime fails, ctime will fail too. This may happen
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# on some platforms.
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pass
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else:
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self.assertEqual(time.ctime(bigval)[-5:], '10000')
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for year in [-100, 100, 1000, 2000, 10000]:
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try:
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testval = time.mktime((year, 1, 10) + (0,)*6)
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except (ValueError, OverflowError):
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# If mktime fails, ctime will fail too. This may happen
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# on some platforms.
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pass
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else:
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self.assertEqual(time.ctime(testval)[20:], str(year))
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@unittest.skipIf(not hasattr(time, "tzset"),
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"time module has no attribute tzset")
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@ -239,14 +242,14 @@ class TimeTestCase(unittest.TestCase):
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gt1 = time.gmtime(None)
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t0 = time.mktime(gt0)
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t1 = time.mktime(gt1)
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self.assertTrue(0 <= (t1-t0) < 0.2)
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self.assertAlmostEqual(t1, t0, delta=0.2)
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def test_localtime_without_arg(self):
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lt0 = time.localtime()
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lt1 = time.localtime(None)
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t0 = time.mktime(lt0)
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t1 = time.mktime(lt1)
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self.assertTrue(0 <= (t1-t0) < 0.2)
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self.assertAlmostEqual(t1, t0, delta=0.2)
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class TestLocale(unittest.TestCase):
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def setUp(self):
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@ -274,16 +277,18 @@ class TestAccept2Year(unittest.TestCase):
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time.accept2dyear = self.saved_accept2dyear
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def yearstr(self, y):
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return time.strftime('%Y', (y,) + (0,) * 8)
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# return time.strftime('%Y', (y,) + (0,) * 8)
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return time.asctime((y,) + (0,) * 8).split()[-1]
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def test_2dyear(self):
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self.assertEqual(self.yearstr(0), '2000')
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self.assertEqual(self.yearstr(69), '1969')
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self.assertEqual(self.yearstr(68), '2068')
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self.assertEqual(self.yearstr(99), '1999')
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with support.check_warnings():
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self.assertEqual(self.yearstr(0), '2000')
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self.assertEqual(self.yearstr(69), '1969')
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self.assertEqual(self.yearstr(68), '2068')
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self.assertEqual(self.yearstr(99), '1999')
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def test_invalid(self):
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self.assertRaises(ValueError, self.yearstr, 1899)
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self.assertRaises(ValueError, self.yearstr, 999)
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self.assertRaises(ValueError, self.yearstr, 100)
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self.assertRaises(ValueError, self.yearstr, -1)
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@ -293,10 +298,15 @@ class TestAccept2YearBool(TestAccept2Year):
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class TestDontAccept2Year(TestAccept2Year):
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accept2dyear = 0
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def test_2dyear(self):
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self.assertRaises(ValueError, self.yearstr, 0)
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self.assertRaises(ValueError, self.yearstr, 69)
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self.assertRaises(ValueError, self.yearstr, 68)
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self.assertRaises(ValueError, self.yearstr, 99)
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self.assertEqual(self.yearstr(0), '0')
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self.assertEqual(self.yearstr(69), '69')
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self.assertEqual(self.yearstr(68), '68')
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self.assertEqual(self.yearstr(99), '99')
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self.assertEqual(self.yearstr(999), '999')
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self.assertEqual(self.yearstr(9999), '9999')
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def test_invalid(self):
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pass
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class TestDontAccept2YearBool(TestDontAccept2Year):
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accept2dyear = False
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@ -36,6 +36,14 @@ Core and Builtins
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Library
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-------
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- Issue #10827: Changed the rules for 2-digit years. The time.asctime
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function will now format any year when ``time.accept2dyear`` is
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false and will accept years >= 1000 otherwise. The year range
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accepted by ``time.mktime`` and ``time.strftime`` is still system
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dependent, but ``time.mktime`` will now accept full range supported
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by the OS. Conversion of 2-digit years to 4-digit is deprecated.
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- Issue #7858: Raise an error properly when os.utime() fails under Windows
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on an existing file.
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@ -312,34 +312,42 @@ gettmarg(PyObject *args, struct tm *p)
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&p->tm_wday, &p->tm_yday, &p->tm_isdst))
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return 0;
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/* XXX: Why 1900? If the goal is to interpret 2-digit years as those in
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* 20th / 21st century according to the POSIX standard, we can just treat
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* 0 <= y < 100 as special. Year 100 is probably too ambiguous and should
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* be rejected, but years 101 through 1899 can be passed through.
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/* If year is specified with less than 4 digits, its interpretation
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* depends on the accept2dyear value.
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*
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* If accept2dyear is true (default), a backward compatibility behavior is
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* invoked as follows:
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*
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* - for 2-digit year, century is guessed according to POSIX rules for
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* %y strptime format: 21st century for y < 69, 20th century
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* otherwise. A deprecation warning is issued when century
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* information is guessed in this way.
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*
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* - for 3-digit or negative year, a ValueError exception is raised.
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*
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* If accept2dyear is false (set by the program or as a result of a
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* non-empty value assigned to PYTHONY2K environment variable) all year
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* values are interpreted as given.
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*/
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if (y < 1900) {
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if (y < 1000) {
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PyObject *accept = PyDict_GetItemString(moddict,
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"accept2dyear");
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int acceptval = accept != NULL && PyObject_IsTrue(accept);
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if (acceptval == -1)
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return 0;
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if (acceptval) {
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if (69 <= y && y <= 99)
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y += 1900;
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else if (0 <= y && y <= 68)
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if (0 <= y && y < 69)
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y += 2000;
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else if (69 <= y && y < 100)
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y += 1900;
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else {
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PyErr_SetString(PyExc_ValueError,
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"year out of range");
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return 0;
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}
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}
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/* XXX: When accept2dyear is false, we don't have to reject y < 1900.
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* Consider removing the following else-clause. */
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else {
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PyErr_SetString(PyExc_ValueError,
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"year out of range");
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return 0;
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if (PyErr_WarnEx(PyExc_DeprecationWarning,
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"Century info guessed for a 2-digit year.", 1) != 0)
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return 0;
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}
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}
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p->tm_year = y - 1900;
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else if (!gettmarg(tup, &buf) || !checktm(&buf))
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return NULL;
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/* XXX: Reportedly, some systems have issues formating dates prior to year
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* 1900. These systems should be identified and this check should be
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* moved to appropriate system specific section below. */
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if (buf.tm_year < 0) {
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PyErr_Format(PyExc_ValueError, "year=%d is before 1900; "
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"the strftime() method requires year >= 1900",
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buf.tm_year + 1900);
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}
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/* Normalize tm_isdst just in case someone foolishly implements %Z
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based on the assumption that tm_isdst falls within the range of
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[-1, 1] */
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