Python dateutils 根据 iCalendar 格式打印重复规则（参见 RFC 5545）

Question

我正在尝试将重复规则打印为 iCalendar 格式指定的字符串（请参阅RFC 5545）。我使用 python dateutils，特别是 dateutil.rrule 来创建重复规则，我想将其打印为如下字符串：

    "RRULE:FREQ=DAILY;COUNT=5"

谁能告诉我有没有办法做到这一点？

我想我正在使用 labix dateutils btw。

非常感谢！

Answer 1

python-dateutil 包中没有执行此操作的方法或函数。请参阅此错误以获取可能有帮助的补丁：https://bugs.launchpad.net/dateutil/+bug/943512。

Answer 2

这是rrule 的子类，它包含两个建议的python-dateutil 补丁，可以启用rrule 输出。请注意，补丁未被接受可能有充分的理由，我仅针对最简单的情况进行了测试。不处理线折叠。

请参阅错误跟踪器进行讨论： https://bugs.launchpad.net/dateutil/+bug/943512
https://bugs.launchpad.net/dateutil/+bug/943509

FREQNAMES = ['YEARLY', 'MONTHLY', 'WEEKLY', 'DAILY', 'HOURLY', 'MINUTELY', 'SECONDLY']


class ConvertibleRRule(rrule.rrule):
    # Subclass of the `rrule class that provides a sensible __str__()
    # method, outputting ical formatted rrules.
    # Combined from the patches in these dateutil issues:
    #  https://bugs.launchpad.net/dateutil/+bug/943512
    #  https://bugs.launchpad.net/dateutil/+bug/943509
    _bysecond_internal = False
    _byminute_internal = False
    _byhour = False
    _bymonth_internal = False
    _bymonthday_internal = False
    _byweekday_internal = False

    def __init__(self, freq, dtstart=None,
                 interval=1, wkst=None, count=None, until=None, bysetpos=None,
                 bymonth=None, bymonthday=None, byyearday=None, byeaster=None,
                 byweekno=None, byweekday=None,
                 byhour=None, byminute=None, bysecond=None,
                 cache=False):
        super(ConvertibleRRule, self).__init__(
            freq, dtstart=dtstart,
            interval=interval, wkst=wkst, count=count, until=until, bysetpos=bysetpos,
            bymonth=bymonth, bymonthday=bymonthday, byyearday=byyearday, byeaster=byeaster,
            byweekno=byweekno, byweekday=byweekday,
            byhour=byhour, byminute=byminute, bysecond=bysecond,
            cache=cache)

        if (byweekno is None and byyearday is None and bymonthday is None and
                    byweekday is None and byeaster is None):
            if freq == rrule.YEARLY:
                if not bymonth:
                    self._bymonth_internal = True
                self._bymonthday_internal = True
            elif freq == rrule.MONTHLY:
                self._bymonthday_internal = True
            elif freq == rrule.WEEKLY:
                self._byweekday_internal = True

        # byhour
        if byhour is None:
            if freq < rrule.HOURLY:
                self._byhour_internal = True

        # byminute
        if byminute is None:
            if freq < rrule.MINUTELY:
                self._byminute_internal = True

        # bysecond
        if bysecond is None:
            if freq < rrule.SECONDLY:
                self._bysecond_internal = True

    freq = property(lambda s: s._freq)
    dtstart = property(lambda s: s._dtstart)
    interval = property(lambda s: s._interval)

    @property
    def wkst(self):
        if self._wkst == rrule.calendar.firstweekday():
            return None
        return rrule.weekday(self._wkst)

    count = property(lambda s: s._count)
    until = property(lambda s: s._until)
    bysetpos = property(lambda s: s._bysetpos)

    @property
    def bymonth(self):
        if self._bymonth_internal:
            return None
        return self._bymonth

    @property
    def bymonthday(self):
        if self._bymonthday_internal:
            return None
        return self._bymonthday + self._bynmonthday

    byyearday = property(lambda s: s._byyearday)
    byeaster = property(lambda s: s._byeaster)
    byweekno = property(lambda s: s._byweekno)

    @property
    def byweekday(self):
        if self._byweekday_internal:
            return None
        bynweekday, byweekday = (), ()
        if self._bynweekday:
            bynweekday = tuple(rrule.weekday(d, n) for d, n in self._bynweekday)
        if self._byweekday:
            byweekday = tuple(rrule.weekday(d) for d in self._byweekday)
        return bynweekday + byweekday

    @property
    def byhour(self):
        if self._byhour_internal:
            return None
        return self._byhour

    @property
    def byminute(self):
        if self._byminute_internal:
            return None
        return self._byminute

    @property
    def bysecond(self):
        if self._bysecond_internal:
            return None
        return self._bysecond

    def __str__(self):
        parts = ['FREQ=' + FREQNAMES[self.freq]]

        if self.interval != 1:
            parts.append('INTERVAL=' + str(self.interval))
        if self.wkst:
            parts.append('WKST=' + str(self.wkst))
        if self.count:
            parts.append('COUNT=' + str(self.count))

        for name, value in [
            ('BYSETPOS', self.bysetpos),
            ('BYMONTH', self.bymonth),
            ('BYMONTHDAY', self.bymonthday),
            ('BYYEARDAY', self.byyearday),
            ('BYWEEKNO', self.byweekno),
            ('BYWEEKDAY', self.byweekday),
            ('BYHOUR', self.byhour),
            ('BYMINUTE', self.byminute),
            ('BYSECOND', self.bysecond),
        ]:
            if value:
                parts.append(name + '=' + ','.join(str(v) for v in value))

        return ';'.join(parts)

Answer 3

虽然这是在提出问题四年后写的，dateutil 现在有一个__str__ 方法（参见source code），它允许print 它的对象以这样的形式：

In [1]: from dateutil.rrule import *

In [2]: my_rrule = rrule(DAILY, count=5)

In [3]: print(my_rrule)
DTSTART:20161202T184513
FREQ=DAILY;COUNT=5