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Clarify what changed with respect to date ranges and two-digit years.

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Raymond Hettinger 2011-01-21 03:00:00 +00:00
parent 305bc9e0e8
commit f1dae31ea6
1 changed files with 22 additions and 15 deletions
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Doc/whatsnew/3.2.rst
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@ -489,8 +489,7 @@ Some smaller changes made to the core Python language are:
original object. original object.
>>> with memoryview(b'abcdefgh') as v: >>> with memoryview(b'abcdefgh') as v:
... print(v.tolist()) print(v.tolist())
...
[97, 98, 99, 100, 101, 102, 103, 104] [97, 98, 99, 100, 101, 102, 103, 104]
(Added by Antoine Pitrou; :issue:`9757`.) (Added by Antoine Pitrou; :issue:`9757`.)
@ -934,20 +933,28 @@ datetime and time
* The :meth:`datetime.date.strftime` method is no longer restricted to years * The :meth:`datetime.date.strftime` method is no longer restricted to years
after 1900. The new supported year range is from 1000 to 9999 inclusive. after 1900. The new supported year range is from 1000 to 9999 inclusive.
* The rules for two-digit years in time tuples have changed. Now, the * Whenever a two-digit year is used in a time tuple, the interpretation has been
:func:`time.asctime`, :func:`time.strftime` and :func:`time.mktime` governed by :attr:`time.accept2dyear`. The default is *True* which means that
functions will accept any two- or four-digit year when for a two-digit year, the century is guessed according to the POSIX rules
:attr:`time.accept2dyear` is true. Two-digit years are converted to governing the ``%y`` strptime format.
four-digits using the same heuristics as before, but a deprecation
warning will be issued whenever such conversion occurs.
* The :func:`time.asctime`, :func:`time.mktime`, and Starting with Py3.2, use of the century guessing heuristic will emit a
:func:`time.strftime` functions are no longer restricted to years :exc:`DeprecationWarning`. Instead, it is recommended that
after 1900. Now, when :attr:`time.accept2dyear` is false, the :attr:`time.accept2dyear` be set to *False* so that large date ranges
:func:`time.asctime` function will accept any year that fits in can be used without guesswork:
a C int, while :func:`time.mktime` and :func:`time.strftime`
functions will accept full range supported by the corresponding >>> time.accept2dyear = 1 # guess whether 11 means 11 or 2011
operating system functions. >>> time.asctime((11, 1, 1, 12, 34, 56, 4, 1, 0))
'Fri Jan 1 12:34:56 2011'
>>> time.accept2dyear = 0 # use the full range of allowable dates
>>> time.asctime((11, 1, 1, 12, 34, 56, 4, 1, 0))
'Fri Jan 1 12:34:56 11'
Several functions now have significantly expanded date ranges. When
:attr:`time.accept2dyear` is false, the :func:`time.asctime` function will
accept any year that fits in a C int, while the :func:`time.mktime` and
:func:`time.strftime` functions will accept the full range supported by the
corresponding operating system functions.
(Contributed by Alexander Belopolsky and Victor Stinner.) (Contributed by Alexander Belopolsky and Victor Stinner.)