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bpo-36004: Add date.fromisocalendar (GH-11888)

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This commit implements the first version of date.fromisocalendar, the
inverse function for date.isocalendar.
This commit is contained in:
Paul Ganssle 2019-04-29 09:22:03 -04:00 • committed by Victor Stinner
parent a86e06433a
commit 88c0937056
6 changed files with 209 additions and 0 deletions
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67
Modules/_datetimemodule.c
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@ -3003,6 +3003,67 @@ invalid_string_error:
return NULL;
}
static PyObject *
date_fromisocalendar(PyObject *cls, PyObject *args, PyObject *kw)
{
static char *keywords[] = {
"year", "week", "day", NULL
};
int year, week, day;
if (PyArg_ParseTupleAndKeywords(args, kw, "iii:fromisocalendar",
keywords,
&year, &week, &day) == 0) {
if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
PyErr_Format(PyExc_ValueError,
"ISO calendar component out of range");
}
return NULL;
}
// Year is bounded to 0 < year < 10000 because 9999-12-31 is (9999, 52, 5)
if (year < MINYEAR || year > MAXYEAR) {
PyErr_Format(PyExc_ValueError, "Year is out of range: %d", year);
return NULL;
}
if (week <= 0 || week >= 53) {
int out_of_range = 1;
if (week == 53) {
// ISO years have 53 weeks in it on years starting with a Thursday
// and on leap years starting on Wednesday
int first_weekday = weekday(year, 1, 1);
if (first_weekday == 3 || (first_weekday == 2 && is_leap(year))) {
out_of_range = 0;
}
}
if (out_of_range) {
PyErr_Format(PyExc_ValueError, "Invalid week: %d", week);
return NULL;
}
}
if (day <= 0 || day >= 8) {
PyErr_Format(PyExc_ValueError, "Invalid day: %d (range is [1, 7])",
day);
return NULL;
}
// Convert (Y, W, D) to (Y, M, D) in-place
int day_1 = iso_week1_monday(year);
int month = week;
int day_offset = (month - 1)*7 + day - 1;
ord_to_ymd(day_1 + day_offset, &year, &month, &day);
return new_date_subclass_ex(year, month, day, cls);
}
/*
* Date arithmetic.
*/
@ -3296,6 +3357,12 @@ static PyMethodDef date_methods[] = {
METH_CLASS,
PyDoc_STR("str -> Construct a date from the output of date.isoformat()")},
{"fromisocalendar", (PyCFunction)(void(*)(void))date_fromisocalendar,
METH_VARARGS | METH_KEYWORDS | METH_CLASS,
PyDoc_STR("int, int, int -> Construct a date from the ISO year, week "
"number and weekday.\n\n"
"This is the inverse of the date.isocalendar() function")},
{"today", (PyCFunction)date_today, METH_NOARGS | METH_CLASS,
PyDoc_STR("Current date or datetime: same as "
"self.__class__.fromtimestamp(time.time()).")},