168 lines
6.5 KiB
Python
168 lines
6.5 KiB
Python
# No part of the content of this file was derived from the works of David Giffin.
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#
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# Copyright © 2005-2008 Stephen John Machin, Lingfo Pty Ltd
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# This module is part of the xlrd3 package, which is released under a
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# BSD-style licence.
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#
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# Provides function(s) for dealing with Microsoft Excel ™ dates.
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#
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# 2008-10-18 SJM Fix bug in xldate_from_date_tuple (affected some years after 2099)
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#
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# The conversion from days to (year, month, day) starts with
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# an integral "julian day number" aka JDN.
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# FWIW, JDN 0 corresponds to noon on Monday November 24 in Gregorian year -4713.
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# More importantly:
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# Noon on Gregorian 1900-03-01 (day 61 in the 1900-based system) is JDN 2415080.0
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# Noon on Gregorian 1904-01-02 (day 1 in the 1904-based system) is JDN 2416482.0
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def ifd(x, y):
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return divmod(x, y)[0]
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_JDN_delta = (2415080 - 61, 2416482 - 1)
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assert _JDN_delta[1] - _JDN_delta[0] == 1462
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class XLDateError(ValueError): pass
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class XLDateNegative(XLDateError): pass
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class XLDateAmbiguous(XLDateError): pass
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class XLDateTooLarge(XLDateError): pass
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class XLDateBadDatemode(XLDateError): pass
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class XLDateBadTuple(XLDateError): pass
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_XLDAYS_TOO_LARGE = (2958466, 2958466 - 1462) # This is equivalent to 10000-01-01
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# Convert an Excel number (presumed to represent a date, a datetime or a time) into
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# a tuple suitable for feeding to datetime or mx.DateTime constructors.
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# @param xldate The Excel number
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# @param datemode 0: 1900-based, 1: 1904-based.
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# <br>WARNING: when using this function to
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# interpret the contents of a workbook, you should pass in the Book.datemode
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# attribute of that workbook. Whether
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# the workbook has ever been anywhere near a Macintosh is irrelevant.
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# @return Gregorian (year, month, day, hour, minute, nearest_second).
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# <br>Special case: if 0.0 <= xldate < 1.0, it is assumed to represent a time;
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# (0, 0, 0, hour, minute, second) will be returned.
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# <br>Note: 1904-01-01 is not regarded as a valid date in the datemode 1 system; its "serial number"
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# is zero.
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# @throws XLDateNegative xldate < 0.00
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# @throws XLDateAmbiguous The 1900 leap-year problem (datemode == 0 and 1.0 <= xldate < 61.0)
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# @throws XLDateTooLarge Gregorian year 10000 or later
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# @throws XLDateBadDatemode datemode arg is neither 0 nor 1
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# @throws XLDateError Covers the 4 specific errors
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def xldate_as_tuple(xldate, datemode):
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if datemode not in (0, 1):
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raise XLDateBadDatemode(datemode)
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if xldate == 0.00:
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return (0, 0, 0, 0, 0, 0)
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if xldate < 0.00:
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raise XLDateNegative(xldate)
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xldays = int(xldate)
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frac = xldate - xldays
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seconds = int(round(frac * 86400.0))
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assert 0 <= seconds <= 86400
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if seconds == 86400:
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hour = minute = second = 0
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xldays += 1
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else:
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# second = seconds % 60; minutes = seconds // 60
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minutes, second = divmod(seconds, 60)
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# minute = minutes % 60; hour = minutes // 60
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hour, minute = divmod(minutes, 60)
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if xldays >= _XLDAYS_TOO_LARGE[datemode]:
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raise XLDateTooLarge(xldate)
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if xldays == 0:
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return (0, 0, 0, hour, minute, second)
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if xldays < 61 and datemode == 0:
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raise XLDateAmbiguous(xldate)
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jdn = xldays + _JDN_delta[datemode]
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yreg = (ifd(ifd(jdn * 4 + 274277, 146097) * 3, 4) + jdn + 1363) * 4 + 3
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mp = ifd(yreg % 1461, 4) * 535 + 333
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d = ifd(mp % 16384, 535) + 1
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# mp /= 16384
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mp >>= 14
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if mp >= 10:
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return (ifd(yreg, 1461) - 4715, mp - 9, d, hour, minute, second)
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else:
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return (ifd(yreg, 1461) - 4716, mp + 3, d, hour, minute, second)
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# === conversions from date/time to xl numbers
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def _leap(y):
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if y % 4: return 0
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if y % 100: return 1
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if y % 400: return 0
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return 1
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_days_in_month = (None, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31)
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# Convert a date tuple (year, month, day) to an Excel date.
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# @param year Gregorian year.
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# @param month 1 <= month <= 12
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# @param day 1 <= day <= last day of that (year, month)
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# @param datemode 0: 1900-based, 1: 1904-based.
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# @throws XLDateAmbiguous The 1900 leap-year problem (datemode == 0 and 1.0 <= xldate < 61.0)
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# @throws XLDateBadDatemode datemode arg is neither 0 nor 1
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# @throws XLDateBadTuple (year, month, day) is too early/late or has invalid component(s)
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# @throws XLDateError Covers the specific errors
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def xldate_from_date_tuple(datetuple, datemode):
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(year, month, day) = datetuple
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if datemode not in (0, 1):
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raise XLDateBadDatemode(datemode)
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if year == 0 and month == 0 and day == 0:
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return 0.00
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if not (1900 <= year <= 9999):
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raise XLDateBadTuple("Invalid year: %r" % ((year, month, day),))
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if not (1 <= month <= 12):
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raise XLDateBadTuple("Invalid month: %r" % ((year, month, day),))
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if day < 1 \
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or (day > _days_in_month[month] and not(day == 29 and month == 2 and _leap(year))):
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raise XLDateBadTuple("Invalid day: %r" % ((year, month, day),))
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Yp = year + 4716
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M = month
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if M <= 2:
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Yp = Yp - 1
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Mp = M + 9
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else:
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Mp = M - 3
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jdn = ifd(1461 * Yp, 4) + ifd(979 * Mp + 16, 32) + \
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day - 1364 - ifd(ifd(Yp + 184, 100) * 3, 4)
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xldays = jdn - _JDN_delta[datemode]
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if xldays <= 0:
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raise XLDateBadTuple("Invalid (year, month, day): %r" % ((year, month, day),))
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if xldays < 61 and datemode == 0:
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raise XLDateAmbiguous("Before 1900-03-01: %r" % ((year, month, day),))
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return float(xldays)
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# Convert a time tuple (hour, minute, second) to an Excel "date" value (fraction of a day).
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# @param hour 0 <= hour < 24
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# @param minute 0 <= minute < 60
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# @param second 0 <= second < 60
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# @throws XLDateBadTuple Out-of-range hour, minute, or second
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def xldate_from_time_tuple(timetuple):
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(hour, minute, second) = timetuple
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if 0 <= hour < 24 and 0 <= minute < 60 and 0 <= second < 60:
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return ((second / 60.0 + minute) / 60.0 + hour) / 24.0
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raise XLDateBadTuple("Invalid (hour, minute, second): %r" % ((hour, minute, second),))
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# Convert a datetime tuple (year, month, day, hour, minute, second) to an Excel date value.
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# For more details, refer to other xldate_from_*_tuple functions.
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# @param datetime_tuple (year, month, day, hour, minute, second)
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# @param datemode 0: 1900-based, 1: 1904-based.
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def xldate_from_datetime_tuple(datetime_tuple, datemode):
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return (
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xldate_from_date_tuple(datetime_tuple[:3], datemode)
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+
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xldate_from_time_tuple(datetime_tuple[3:])
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)
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