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bpo-30802: strptime() directives %W and %U -- Make weekday optional and assume the first day of the week #11594

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bpo-30802: strptime() directives %W and %U -- Make weekday optional and assume the first day of the week #11594

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b12071f
bpo-30802: Relax strptime() reqs for %U and %W
uoqs Jan 17, 2019
f9e4c69
bpo-30802: Update documentation
uoqs Jan 17, 2019
6c9535b
bpo-30802: Add Misc/NEWS message
uoqs Jan 17, 2019
19dd804
bpo-30802: Update documentation
uoqs Nov 17, 2019
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7 changes: 4 additions & 3 deletions Doc/library/datetime.rst
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Expand Up @@ -2251,11 +2251,12 @@ Notes:

(7)
When used with the :meth:`strptime` method, ``%U`` and ``%W`` are only used
in calculations when the day of the week and the calendar year (``%Y``)
are specified.
in calculations when the calendar year (``%Y``) is specified. Optionally the
weekday can also be specified, but if it is omitted then the first day of
the week is assumed.

(8)
Similar to ``%U`` and ``%W``, ``%V`` is only used in calculations when the
``%V`` is only used in calculations when the
day of the week and the ISO year (``%G``) are specified in a
:meth:`strptime` format string. Also note that ``%G`` and ``%Y`` are not
interchangeable.
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10 changes: 6 additions & 4 deletions Lib/_strptime.py
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Expand Up @@ -512,12 +512,14 @@ def _strptime(data_string, format="%a %b %d %H:%M:%S %Y"):
year = 1900


# If we know the week of the year and what day of that week, we can figure
# out the Julian day of the year.
if julian is None and weekday is not None:
# If we know the year, the week, and the day of the week, we can figure out
# the Julian day of the year. If day of the week is not specified for the
# directives %U and %W we assume it to be the first day of the week.
if julian is None:
if week_of_year is not None:
week_starts_Mon = True if week_of_year_start == 0 else False
julian = _calc_julian_from_U_or_W(year, week_of_year, weekday,
day_of_week = week_of_year_start if weekday is None else weekday
julian = _calc_julian_from_U_or_W(year, week_of_year, day_of_week,
week_starts_Mon)
elif iso_year is not None and iso_week is not None:
year, julian = _calc_julian_from_V(iso_year, iso_week, weekday + 1)
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1 change: 1 addition & 0 deletions Misc/ACKS
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Expand Up @@ -177,6 +177,7 @@ Wouter Bolsterlee
Gawain Bolton
Forest Bond
Gregory Bond
Sergey Bondarchuk
Médéric Boquien
Matias Bordese
Jonas Borgström
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4 changes: 4 additions & 0 deletions Misc/NEWS.d/next/Library/2019-01-17-20-24-08.bpo-30802.d41fsC.rst
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@@ -0,0 +1,4 @@
:meth:`datetime.strptime` directives ``%U`` and ``%W`` no longer require a
weekday to be specified in the format string and will assume the first day
of the week if it is omitted (this is not the same as specifying the
weekday).