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Commit88c0937

Browse files
pgansslevstinner
authored andcommitted
bpo-36004: Add date.fromisocalendar (GH-11888)
This commit implements the first version of date.fromisocalendar, theinverse function for date.isocalendar.
1 parenta86e064 commit88c0937

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‎Doc/library/datetime.rst‎

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@@ -458,6 +458,13 @@ Other constructors, all class methods:
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..versionadded::3.7
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..classmethod::date.fromisocalendar(year, week, day)
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Return a:class:`date` corresponding to the ISO calendar date specified by
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year, week and day. This is the inverse of the function:meth:`date.isocalendar`.
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..versionadded::3.8
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Class attributes:
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@@ -854,6 +861,16 @@ Other constructors, all class methods:
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..versionadded::3.7
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..classmethod::datetime.fromisocalendar(year, week, day)
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Return a:class:`datetime` corresponding to the ISO calendar date specified
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by year, week and day. The non-date components of the datetime are populated
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with their normal default values. This is the inverse of the function
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:meth:`datetime.isocalendar`.
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..versionadded::3.8
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..classmethod::datetime.strptime(date_string, format)
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Return a:class:`.datetime` corresponding to *date_string*, parsed according to

‎Doc/whatsnew/3.8.rst‎

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@@ -244,6 +244,16 @@ where the DLL is stored (if a full or partial path is used to load the initial
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DLL) and paths added by:func:`~os.add_dll_directory`.
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datetime
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--------
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Added new alternate constructors:meth:`datetime.date.fromisocalendar` and
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:meth:`datetime.datetime.fromisocalendar`, which construct:class:`date` and
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:class:`datetime` objects respectively from ISO year, week number and weekday;
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these are the inverse of each class's ``isocalendar`` method.
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(Contributed by Paul Ganssle in:issue:`36004`.)
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gettext
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-------
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‎Lib/datetime.py‎

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@@ -884,6 +884,40 @@ def fromisoformat(cls, date_string):
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exceptException:
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raiseValueError(f'Invalid isoformat string:{date_string!r}')
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@classmethod
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deffromisocalendar(cls,year,week,day):
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"""Construct a date from the ISO year, week number and weekday.
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This is the inverse of the date.isocalendar() function"""
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# Year is bounded this way because 9999-12-31 is (9999, 52, 5)
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ifnotMINYEAR<=year<=MAXYEAR:
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raiseValueError(f"Year is out of range:{year}")
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ifnot0<week<53:
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out_of_range=True
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ifweek==53:
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# ISO years have 53 weeks in them on years starting with a
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# Thursday and leap years starting on a Wednesday
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first_weekday=_ymd2ord(year,1,1)%7
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if (first_weekday==4or (first_weekday==3and
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_is_leap(year))):
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out_of_range=False
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ifout_of_range:
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raiseValueError(f"Invalid week:{week}")
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ifnot0<day<8:
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raiseValueError(f"Invalid weekday:{day} (range is [1, 7])")
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# Now compute the offset from (Y, 1, 1) in days:
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day_offset= (week-1)*7+ (day-1)
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# Calculate the ordinal day for monday, week 1
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day_1=_isoweek1monday(year)
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ord_day=day_1+day_offset
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returncls(*_ord2ymd(ord_day))
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# Conversions to string
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@@ -2141,6 +2175,7 @@ def _isoweek1monday(year):
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week1monday+=7
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returnweek1monday
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classtimezone(tzinfo):
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__slots__='_offset','_name'
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‎Lib/test/datetimetester.py‎

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@@ -1795,6 +1795,82 @@ def test_fromisoformat_fails_typeerror(self):
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withself.assertRaises(TypeError):
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self.theclass.fromisoformat(bad_type)
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deftest_fromisocalendar(self):
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# For each test case, assert that fromisocalendar is the
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# inverse of the isocalendar function
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dates= [
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(2016,4,3),
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(2005,1,2),# (2004, 53, 7)
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(2008,12,30),# (2009, 1, 2)
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(2010,1,2),# (2009, 53, 6)
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(2009,12,31),# (2009, 53, 4)
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(1900,1,1),# Unusual non-leap year (year % 100 == 0)
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(1900,12,31),
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(2000,1,1),# Unusual leap year (year % 400 == 0)
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(2000,12,31),
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(2004,1,1),# Leap year
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(2004,12,31),
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(1,1,1),
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(9999,12,31),
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(MINYEAR,1,1),
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(MAXYEAR,12,31),
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]
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fordatecompsindates:
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withself.subTest(datecomps=datecomps):
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dobj=self.theclass(*datecomps)
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isocal=dobj.isocalendar()
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d_roundtrip=self.theclass.fromisocalendar(*isocal)
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self.assertEqual(dobj,d_roundtrip)
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deftest_fromisocalendar_value_errors(self):
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isocals= [
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(2019,0,1),
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(2019,-1,1),
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(2019,54,1),
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(2019,1,0),
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(2019,1,-1),
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(2019,1,8),
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(2019,53,1),
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(10000,1,1),
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(0,1,1),
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(9999999,1,1),
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(2<<32,1,1),
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(2019,2<<32,1),
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(2019,1,2<<32),
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]
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forisocalinisocals:
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withself.subTest(isocal=isocal):
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withself.assertRaises(ValueError):
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self.theclass.fromisocalendar(*isocal)
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deftest_fromisocalendar_type_errors(self):
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err_txformers= [
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str,
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float,
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lambdax:None,
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]
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# Take a valid base tuple and transform it to contain one argument
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# with the wrong type. Repeat this for each argument, e.g.
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# [("2019", 1, 1), (2019, "1", 1), (2019, 1, "1"), ...]
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isocals= []
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base= (2019,1,1)
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foriinrange(3):
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fortxformerinerr_txformers:
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err_val=list(base)
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err_val[i]=txformer(err_val[i])
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isocals.append(tuple(err_val))
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forisocalinisocals:
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withself.subTest(isocal=isocal):
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withself.assertRaises(TypeError):
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self.theclass.fromisocalendar(*isocal)
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#############################################################################
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# datetime tests
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@@ -0,0 +1,4 @@
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Added new alternate constructors:meth:`datetime.date.fromisocalendar` and
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:meth:`datetime.datetime.fromisocalendar`, which construct date objects from
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ISO year, week number and weekday; these are the inverse of each class's
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``isocalendar`` method. Patch by Paul Ganssle.

‎Modules/_datetimemodule.c‎

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@@ -3003,6 +3003,67 @@ date_fromisoformat(PyObject *cls, PyObject *dtstr)
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returnNULL;
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}
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staticPyObject*
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date_fromisocalendar(PyObject*cls,PyObject*args,PyObject*kw)
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{
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staticchar*keywords[]= {
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"year","week","day",NULL
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};
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intyear,week,day;
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if (PyArg_ParseTupleAndKeywords(args,kw,"iii:fromisocalendar",
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keywords,
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&year,&week,&day)==0) {
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if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
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PyErr_Format(PyExc_ValueError,
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"ISO calendar component out of range");
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}
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returnNULL;
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}
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// Year is bounded to 0 < year < 10000 because 9999-12-31 is (9999, 52, 5)
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if (year<MINYEAR||year>MAXYEAR) {
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PyErr_Format(PyExc_ValueError,"Year is out of range: %d",year);
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returnNULL;
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}
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if (week <=0||week >=53) {
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intout_of_range=1;
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if (week==53) {
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// ISO years have 53 weeks in it on years starting with a Thursday
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// and on leap years starting on Wednesday
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intfirst_weekday=weekday(year,1,1);
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if (first_weekday==3|| (first_weekday==2&&is_leap(year))) {
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out_of_range=0;
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}
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}
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if (out_of_range) {
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PyErr_Format(PyExc_ValueError,"Invalid week: %d",week);
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returnNULL;
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}
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}
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if (day <=0||day >=8) {
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PyErr_Format(PyExc_ValueError,"Invalid day: %d (range is [1, 7])",
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day);
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returnNULL;
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}
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// Convert (Y, W, D) to (Y, M, D) in-place
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intday_1=iso_week1_monday(year);
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intmonth=week;
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intday_offset= (month-1)*7+day-1;
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ord_to_ymd(day_1+day_offset,&year,&month,&day);
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returnnew_date_subclass_ex(year,month,day,cls);
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}
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/*
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* Date arithmetic.
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*/
@@ -3296,6 +3357,12 @@ static PyMethodDef date_methods[] = {
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METH_CLASS,
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PyDoc_STR("str -> Construct a date from the output of date.isoformat()")},
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{"fromisocalendar", (PyCFunction)(void(*)(void))date_fromisocalendar,
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METH_VARARGS |METH_KEYWORDS |METH_CLASS,
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PyDoc_STR("int, int, int -> Construct a date from the ISO year, week "
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"number and weekday.\n\n"
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"This is the inverse of the date.isocalendar() function")},
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{"today", (PyCFunction)date_today,METH_NOARGS |METH_CLASS,
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PyDoc_STR("Current date or datetime: same as "
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"self.__class__.fromtimestamp(time.time()).")},

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