150 lines
6.5 KiB
Python
150 lines
6.5 KiB
Python
##############################################################################
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# Copyright 2009, Gerhard Weis
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions are met:
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#
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# * Redistributions of source code must retain the above copyright notice,
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# this list of conditions and the following disclaimer.
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# * Redistributions in binary form must reproduce the above copyright notice,
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# this list of conditions and the following disclaimer in the documentation
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# and/or other materials provided with the distribution.
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# * Neither the name of the authors nor the names of its contributors
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# may be used to endorse or promote products derived from this software
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# without specific prior written permission.
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#
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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# CONTRACT, STRICT LIABILITY, OR TORT
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##############################################################################
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'''
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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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from datetime import timedelta
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from decimal import Decimal
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import re
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from isodate.duration import Duration
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from isodate.isoerror import ISO8601Error
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from isodate.isodatetime import parse_datetime
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from isodate.isostrf import strftime, D_DEFAULT
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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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# regular expression to parse ISO duartion strings.
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def parse_duration(datestring):
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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, basestring):
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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 durdt.year != 0 or durdt.month != 0:
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# create Duration
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ret = Duration(days=durdt.day, seconds=durdt.second,
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microseconds=durdt.microsecond,
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minutes=durdt.minute, hours=durdt.hour,
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months=durdt.month, years=durdt.year)
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else: # FIXME: currently not possible in alternative format
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# create timedelta
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ret = timedelta(days=durdt.day, seconds=durdt.second,
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microseconds=durdt.microsecond,
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minutes=durdt.minute, hours=durdt.hour)
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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 groups["years"] == 0 and groups["months"] == 0:
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ret = timedelta(days=groups["days"], hours=groups["hours"],
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minutes=groups["minutes"], seconds=groups["seconds"],
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weeks=groups["weeks"])
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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(years=groups["years"], months=groups["months"],
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days=groups["days"], hours=groups["hours"],
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minutes=groups["minutes"], seconds=groups["seconds"],
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weeks=groups["weeks"])
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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 (((isinstance(tduration, Duration) and
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(tduration.years < 0 or tduration.months < 0 or
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tduration.tdelta < timedelta(0))) or
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(isinstance(tduration, timedelta) and
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(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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