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gh-80010: Expand fromisoformat to include most of ISO-8601 (#92177)
This expands `fromisoformat` to cover most of the common uses of ISO 8601. We may expand the scope more in the future.
This commit is contained in:
Paul Ganssle
GitHub
parent
ada8b6d1b1
commit
1303f8c927
6 changed files with 778 additions and 178 deletions
252
Lib/datetime.py
252
Lib/datetime.py
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@ -262,58 +262,150 @@ def _wrap_strftime(object, format, timetuple):
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return _time.strftime(newformat, timetuple)
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# Helpers for parsing the result of isoformat()
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def _is_ascii_digit(c):
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return c in "0123456789"
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def _find_isoformat_datetime_separator(dtstr):
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# See the comment in _datetimemodule.c:_find_isoformat_datetime_separator
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len_dtstr = len(dtstr)
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if len_dtstr == 7:
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return 7
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assert len_dtstr > 7
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date_separator = "-"
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week_indicator = "W"
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if dtstr[4] == date_separator:
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if dtstr[5] == week_indicator:
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if len_dtstr < 8:
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raise ValueError("Invalid ISO string")
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if len_dtstr > 8 and dtstr[8] == date_separator:
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if len_dtstr == 9:
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raise ValueError("Invalid ISO string")
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if len_dtstr > 10 and _is_ascii_digit(dtstr[10]):
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# This is as far as we need to resolve the ambiguity for
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# the moment - if we have YYYY-Www-##, the separator is
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# either a hyphen at 8 or a number at 10.
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#
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# We'll assume it's a hyphen at 8 because it's way more
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# likely that someone will use a hyphen as a separator than
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# a number, but at this point it's really best effort
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# because this is an extension of the spec anyway.
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# TODO(pganssle): Document this
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return 8
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return 10
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else:
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# YYYY-Www (8)
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return 8
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else:
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# YYYY-MM-DD (10)
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return 10
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else:
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if dtstr[4] == week_indicator:
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# YYYYWww (7) or YYYYWwwd (8)
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idx = 7
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while idx < len_dtstr:
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if not _is_ascii_digit(dtstr[idx]):
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break
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idx += 1
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if idx < 9:
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return idx
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if idx % 2 == 0:
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# If the index of the last number is even, it's YYYYWwwd
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return 7
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else:
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return 8
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else:
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# YYYYMMDD (8)
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return 8
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def _parse_isoformat_date(dtstr):
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# It is assumed that this function will only be called with a
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# string of length exactly 10, and (though this is not used) ASCII-only
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# It is assumed that this is an ASCII-only string of lengths 7, 8 or 10,
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# see the comment on Modules/_datetimemodule.c:_find_isoformat_datetime_separator
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assert len(dtstr) in (7, 8, 10)
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year = int(dtstr[0:4])
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if dtstr[4] != '-':
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raise ValueError('Invalid date separator: %s' % dtstr[4])
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has_sep = dtstr[4] == '-'
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month = int(dtstr[5:7])
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pos = 4 + has_sep
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if dtstr[pos:pos + 1] == "W":
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# YYYY-?Www-?D?
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pos += 1
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weekno = int(dtstr[pos:pos + 2])
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pos += 2
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if dtstr[7] != '-':
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raise ValueError('Invalid date separator')
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dayno = 1
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if len(dtstr) > pos:
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if (dtstr[pos:pos + 1] == '-') != has_sep:
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raise ValueError("Inconsistent use of dash separator")
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day = int(dtstr[8:10])
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pos += has_sep
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dayno = int(dtstr[pos:pos + 1])
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return list(_isoweek_to_gregorian(year, weekno, dayno))
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else:
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month = int(dtstr[pos:pos + 2])
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pos += 2
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if (dtstr[pos:pos + 1] == "-") != has_sep:
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raise ValueError("Inconsistent use of dash separator")
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pos += has_sep
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day = int(dtstr[pos:pos + 2])
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return [year, month, day]
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_FRACTION_CORRECTION = [100000, 10000, 1000, 100, 10]
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return [year, month, day]
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def _parse_hh_mm_ss_ff(tstr):
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# Parses things of the form HH[:MM[:SS[.fff[fff]]]]
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# Parses things of the form HH[:?MM[:?SS[{.,}fff[fff]]]]
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len_str = len(tstr)
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time_comps = [0, 0, 0, 0]
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pos = 0
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for comp in range(0, 3):
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if (len_str - pos) < 2:
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raise ValueError('Incomplete time component')
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raise ValueError("Incomplete time component")
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time_comps[comp] = int(tstr[pos:pos+2])
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pos += 2
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next_char = tstr[pos:pos+1]
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if comp == 0:
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has_sep = next_char == ':'
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if not next_char or comp >= 2:
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break
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if next_char != ':':
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raise ValueError('Invalid time separator: %c' % next_char)
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if has_sep and next_char != ':':
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raise ValueError("Invalid time separator: %c" % next_char)
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pos += 1
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pos += has_sep
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if pos < len_str:
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if tstr[pos] != '.':
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raise ValueError('Invalid microsecond component')
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if tstr[pos] not in '.,':
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raise ValueError("Invalid microsecond component")
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else:
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pos += 1
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len_remainder = len_str - pos
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if len_remainder not in (3, 6):
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raise ValueError('Invalid microsecond component')
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time_comps[3] = int(tstr[pos:])
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if len_remainder == 3:
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time_comps[3] *= 1000
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if len_remainder >= 6:
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to_parse = 6
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else:
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to_parse = len_remainder
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time_comps[3] = int(tstr[pos:(pos+to_parse)])
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if to_parse < 6:
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time_comps[3] *= _FRACTION_CORRECTION[to_parse-1]
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if (len_remainder > to_parse
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and not all(map(_is_ascii_digit, tstr[(pos+to_parse):]))):
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raise ValueError("Non-digit values in unparsed fraction")
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return time_comps
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@ -321,27 +413,34 @@ def _parse_isoformat_time(tstr):
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# Format supported is HH[:MM[:SS[.fff[fff]]]][+HH:MM[:SS[.ffffff]]]
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len_str = len(tstr)
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if len_str < 2:
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raise ValueError('Isoformat time too short')
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raise ValueError("Isoformat time too short")
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# This is equivalent to re.search('[+-]', tstr), but faster
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tz_pos = (tstr.find('-') + 1 or tstr.find('+') + 1)
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# This is equivalent to re.search('[+-Z]', tstr), but faster
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tz_pos = (tstr.find('-') + 1 or tstr.find('+') + 1 or tstr.find('Z') + 1)
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timestr = tstr[:tz_pos-1] if tz_pos > 0 else tstr
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time_comps = _parse_hh_mm_ss_ff(timestr)
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tzi = None
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if tz_pos > 0:
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if tz_pos == len_str and tstr[-1] == 'Z':
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tzi = timezone.utc
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elif tz_pos > 0:
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tzstr = tstr[tz_pos:]
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# Valid time zone strings are:
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# HH len: 2
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# HHMM len: 4
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# HH:MM len: 5
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# HHMMSS len: 6
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# HHMMSS.f+ len: 7+
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# HH:MM:SS len: 8
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# HH:MM:SS.ffffff len: 15
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# HH:MM:SS.f+ len: 10+
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if len(tzstr) not in (5, 8, 15):
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raise ValueError('Malformed time zone string')
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if len(tzstr) in (0, 1, 3):
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raise ValueError("Malformed time zone string")
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tz_comps = _parse_hh_mm_ss_ff(tzstr)
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if all(x == 0 for x in tz_comps):
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tzi = timezone.utc
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else:
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@ -356,6 +455,38 @@ def _parse_isoformat_time(tstr):
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return time_comps
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# tuple[int, int, int] -> tuple[int, int, int] version of date.fromisocalendar
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def _isoweek_to_gregorian(year, week, day):
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# Year is bounded this way because 9999-12-31 is (9999, 52, 5)
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if not MINYEAR <= year <= MAXYEAR:
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raise ValueError(f"Year is out of range: {year}")
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if not 0 < week < 53:
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out_of_range = True
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if week == 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 == 4 or (first_weekday == 3 and
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_is_leap(year))):
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out_of_range = False
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if out_of_range:
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raise ValueError(f"Invalid week: {week}")
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if not 0 < day < 8:
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raise ValueError(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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return _ord2ymd(ord_day)
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# Just raise TypeError if the arg isn't None or a string.
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def _check_tzname(name):
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@ -847,12 +978,14 @@ class date:
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@classmethod
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def fromisoformat(cls, date_string):
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"""Construct a date from the output of date.isoformat()."""
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"""Construct a date from a string in ISO 8601 format."""
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if not isinstance(date_string, str):
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raise TypeError('fromisoformat: argument must be str')
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if len(date_string) not in (7, 8, 10):
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raise ValueError(f'Invalid isoformat string: {date_string!r}')
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try:
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assert len(date_string) == 10
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return cls(*_parse_isoformat_date(date_string))
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except Exception:
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raise ValueError(f'Invalid isoformat string: {date_string!r}')
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@ -862,35 +995,7 @@ class date:
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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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if not MINYEAR <= year <= MAXYEAR:
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raise ValueError(f"Year is out of range: {year}")
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if not 0 < week < 53:
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out_of_range = True
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if week == 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 == 4 or (first_weekday == 3 and
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_is_leap(year))):
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out_of_range = False
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if out_of_range:
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raise ValueError(f"Invalid week: {week}")
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if not 0 < day < 8:
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raise ValueError(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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return cls(*_ord2ymd(ord_day))
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return cls(*_isoweek_to_gregorian(year, week, day))
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# Conversions to string
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@ -1427,10 +1532,15 @@ class time:
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@classmethod
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def fromisoformat(cls, time_string):
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"""Construct a time from the output of isoformat()."""
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"""Construct a time from a string in one of the ISO 8601 formats."""
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if not isinstance(time_string, str):
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raise TypeError('fromisoformat: argument must be str')
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# The spec actually requires that time-only ISO 8601 strings start with
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# T, but the extended format allows this to be omitted as long as there
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# is no ambiguity with date strings.
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time_string = time_string.removeprefix('T')
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try:
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return cls(*_parse_isoformat_time(time_string))
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except Exception:
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@ -1711,24 +1821,30 @@ class datetime(date):
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@classmethod
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def fromisoformat(cls, date_string):
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"""Construct a datetime from the output of datetime.isoformat()."""
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"""Construct a datetime from a string in one of the ISO 8601 formats."""
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if not isinstance(date_string, str):
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raise TypeError('fromisoformat: argument must be str')
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# Split this at the separator
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dstr = date_string[0:10]
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tstr = date_string[11:]
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if len(date_string) < 7:
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raise ValueError(f'Invalid isoformat string: {date_string!r}')
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# Split this at the separator
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try:
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separator_location = _find_isoformat_datetime_separator(date_string)
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dstr = date_string[0:separator_location]
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tstr = date_string[(separator_location+1):]
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date_components = _parse_isoformat_date(dstr)
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except ValueError:
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raise ValueError(f'Invalid isoformat string: {date_string!r}')
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raise ValueError(
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f'Invalid isoformat string: {date_string!r}') from None
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if tstr:
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try:
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time_components = _parse_isoformat_time(tstr)
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except ValueError:
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raise ValueError(f'Invalid isoformat string: {date_string!r}')
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raise ValueError(
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f'Invalid isoformat string: {date_string!r}') from None
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else:
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time_components = [0, 0, 0, 0, None]
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@ -2509,7 +2625,9 @@ else:
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_format_time, _format_offset, _index, _is_leap, _isoweek1monday, _math,
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_ord2ymd, _time, _time_class, _tzinfo_class, _wrap_strftime, _ymd2ord,
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_divide_and_round, _parse_isoformat_date, _parse_isoformat_time,
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_parse_hh_mm_ss_ff, _IsoCalendarDate)
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_parse_hh_mm_ss_ff, _IsoCalendarDate, _isoweek_to_gregorian,
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_find_isoformat_datetime_separator, _FRACTION_CORRECTION,
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_is_ascii_digit)
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# XXX Since import * above excludes names that start with _,
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# docstring does not get overwritten. In the future, it may be
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# appropriate to maintain a single module level docstring and
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