148 lines
5.3 KiB
Python
148 lines
5.3 KiB
Python
"""
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This module provides an ISO 8601:2004 duration parser.
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It also provides a wrapper to strftime. This wrapper makes it easier to
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format timedelta or Duration instances as ISO conforming strings.
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"""
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import re
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from datetime import timedelta
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from decimal import Decimal
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from isodate.duration import Duration
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from isodate.isodatetime import parse_datetime
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from isodate.isoerror import ISO8601Error
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from isodate.isostrf import D_DEFAULT, strftime
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ISO8601_PERIOD_REGEX = re.compile(
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r"^(?P<sign>[+-])?"
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r"P(?!\b)"
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r"(?P<years>[0-9]+([,.][0-9]+)?Y)?"
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r"(?P<months>[0-9]+([,.][0-9]+)?M)?"
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r"(?P<weeks>[0-9]+([,.][0-9]+)?W)?"
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r"(?P<days>[0-9]+([,.][0-9]+)?D)?"
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r"((?P<separator>T)(?P<hours>[0-9]+([,.][0-9]+)?H)?"
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r"(?P<minutes>[0-9]+([,.][0-9]+)?M)?"
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r"(?P<seconds>[0-9]+([,.][0-9]+)?S)?)?$"
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)
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# regular expression to parse ISO duration strings.
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def parse_duration(datestring, as_timedelta_if_possible=True):
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"""
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Parses an ISO 8601 durations into datetime.timedelta or Duration objects.
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If the ISO date string does not contain years or months, a timedelta
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instance is returned, else a Duration instance is returned.
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The following duration formats are supported:
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-PnnW duration in weeks
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-PnnYnnMnnDTnnHnnMnnS complete duration specification
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-PYYYYMMDDThhmmss basic alternative complete date format
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-PYYYY-MM-DDThh:mm:ss extended alternative complete date format
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-PYYYYDDDThhmmss basic alternative ordinal date format
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-PYYYY-DDDThh:mm:ss extended alternative ordinal date format
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The '-' is optional.
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Limitations: ISO standard defines some restrictions about where to use
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fractional numbers and which component and format combinations are
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allowed. This parser implementation ignores all those restrictions and
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returns something when it is able to find all necessary components.
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In detail:
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it does not check, whether only the last component has fractions.
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it allows weeks specified with all other combinations
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The alternative format does not support durations with years, months or
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days set to 0.
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"""
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if not isinstance(datestring, str):
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raise TypeError("Expecting a string %r" % datestring)
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match = ISO8601_PERIOD_REGEX.match(datestring)
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if not match:
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# try alternative format:
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if datestring.startswith("P"):
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durdt = parse_datetime(datestring[1:])
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if as_timedelta_if_possible and durdt.year == 0 and durdt.month == 0:
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# FIXME: currently not possible in alternative format
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# create timedelta
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ret = timedelta(
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days=durdt.day,
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seconds=durdt.second,
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microseconds=durdt.microsecond,
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minutes=durdt.minute,
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hours=durdt.hour,
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)
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else:
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# create Duration
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ret = Duration(
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days=durdt.day,
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seconds=durdt.second,
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microseconds=durdt.microsecond,
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minutes=durdt.minute,
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hours=durdt.hour,
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months=durdt.month,
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years=durdt.year,
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)
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return ret
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raise ISO8601Error("Unable to parse duration string %r" % datestring)
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groups = match.groupdict()
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for key, val in groups.items():
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if key not in ("separator", "sign"):
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if val is None:
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groups[key] = "0n"
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# print groups[key]
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if key in ("years", "months"):
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groups[key] = Decimal(groups[key][:-1].replace(",", "."))
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else:
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# these values are passed into a timedelta object,
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# which works with floats.
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groups[key] = float(groups[key][:-1].replace(",", "."))
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if as_timedelta_if_possible and groups["years"] == 0 and groups["months"] == 0:
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ret = timedelta(
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days=groups["days"],
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hours=groups["hours"],
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minutes=groups["minutes"],
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seconds=groups["seconds"],
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weeks=groups["weeks"],
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)
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if groups["sign"] == "-":
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ret = timedelta(0) - ret
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else:
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ret = Duration(
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years=groups["years"],
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months=groups["months"],
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days=groups["days"],
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hours=groups["hours"],
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minutes=groups["minutes"],
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seconds=groups["seconds"],
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weeks=groups["weeks"],
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)
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if groups["sign"] == "-":
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ret = Duration(0) - ret
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return ret
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def duration_isoformat(tduration, format=D_DEFAULT):
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"""
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Format duration strings.
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This method is just a wrapper around isodate.isostrf.strftime and uses
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P%P (D_DEFAULT) as default format.
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"""
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# TODO: implement better decision for negative Durations.
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# should be done in Duration class in consistent way with timedelta.
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if (
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isinstance(tduration, Duration)
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and (
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tduration.years < 0
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or tduration.months < 0
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or tduration.tdelta < timedelta(0)
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)
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) or (isinstance(tduration, timedelta) and (tduration < timedelta(0))):
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ret = "-"
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else:
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ret = ""
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ret += strftime(tduration, format)
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return ret
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