django-eventtools is a lightweight library designed to handle repeating and one-off event occurrences for display on a website.

Download the source from https://pypi.python.org/pypi/django-eventtools/ and run python setup.py install, or:

> pip install django-eventtools

Django 1.8 or higher is required.

Given the following models:

from django.db import models

from eventtools.models import BaseEvent, BaseOccurrence


class MyEvent(BaseEvent):
    title = models.CharField(max_length=100)


class MyOccurrence(BaseOccurrence):
    event = models.ForeignKey(MyEvent)

Create a sample event & occurrences

>>> from datetime import datetime
>>> from myapp.models import MyEvent
>>> event = MyEvent.objects.create(title='Test event')
>>> once_off = MyOccurrence.objects.create(
        event=event,
        start=datetime(2016, 1, 1, 12, 0),
        end=datetime(2016, 1, 1, 2, 0))
>>> christmas = MyOccurrence.objects.create(
        event=event,
        start=datetime(2015, 12, 25, 7, 0),
        end=datetime(2015, 12, 25, 22, 0),
        repeat='RRULE:FREQ=YEARLY')
>>> daily = MyOccurrence.objects.create(
        event=event,
        start=datetime(2016, 1, 1, 7, 0),
        end=datetime(2016, 1, 1, 8, 0),
        repeat='RRULE:FREQ=DAILY')

Event and Occurrence instances, and their associated querysets, all support the all_occurrences method, which takes two optional arguments - from_date and to_date, which may be dates or datetimes. from_date and to_date default to None. The method returns a python generator yielding tuples in the format (start, end, instance) - for example:

>>> MyEvent.objects.all().all_occurrences()
>>> event.all_occurrences(from_date=datetime(2015, 1, 1, 10, 0))
>>> event.occurrence_set.all().all_occurrences(to_date=date(2016, 1, 1))
>>> occurrence.all_occurrences(from_date=date(2016, 1, 1),
                               to_date=date(2016, 12, 31))

instance is an instance of the corresponding BaseOccurrence subclass.

A next_occurrence method is also provided, taking the same arguments, but returning a single occurrence tuple.

>>> event.next_occurrence()
>>> event.next_occurrence(from_date=date(2016, 1, 1))

The method first_occurrence also returns a single occurrence tuple, but takes no arguments.

Event and Occurrence querysets can be filtered, but due to uncertainty with repetitions, from_date filtering is only an approximation (whereas to_date filtering is accurate). If you need a queryset filtered exactly, pass exact=True - this will filter using generated occurrences but still return a queryset - but be careful with this as it may be very slow and/or CPU-hungry. For example

>>> MyEvent.objects.for_period(from_date=date(2015, 1, 1),
                             to_date=date(2015, 12, 31))
>>> event.occurrence_set.for_period(from_date=date(2015, 1, 1), exact=True)

Event and Occurrence querysets can also be sorted by their next occurrence using the sort_by_next method. By default this sorts instances by their first occurrence; the optional from_date argument will sort by the next occurrence after from_date. For example

>>> MyEvent.objects.all().sort_by_next()
>>> event.occurrence_set.for_period(from_date=date(2015, 1, 1)) \
>>>      .sort_by_next(date(2015, 1, 1))

Note that this method returns a sorted list, not a queryset.

Occurrences can repeat using any interval that can be expressed as an rrulestr. To customise the available options, set EVENTTOOLS_REPEAT_CHOICES in your django settings. The default value is

EVENTTOOLS_REPEAT_CHOICES = (
    ("RRULE:FREQ=DAILY", 'Daily'),
    ("RRULE:FREQ=WEEKLY", 'Weekly'),
    ("RRULE:FREQ=MONTHLY", 'Monthly'),
    ("RRULE:FREQ=YEARLY", 'Yearly'),
)

Set EVENTTOOLS_REPEAT_CHOICES = None to make repeat a plain-text field.

Cancelling or modifying a single occurrence repetition is not currently supported, but can be implemented by overriding a couple of methods. For example, the following allows cancellations or one-off modifications to the start time of a repetition:

from eventtools.models import (BaseEvent, BaseOccurrence, default_naive)
from django.db import models


class MyEvent(BaseEvent):
	pass


class MyEventOccurrence(BaseOccurrence):
    event = models.ForeignKey(MyEvent)
    overrides = models.ManyToManyField('MyEventOccurrenceOverride', blank=True)

    def get_repeater(self):
        rule = super().get_repeater()  # gets rruleset from parent method
        ruleset.rrule(rule)
        for override in self.overrides.all():
            ruleset.exdate(default_naive(override.start))  # remove occurrence
            if override.modified_start:  # reschedule occurrence if defined
                ruleset.rdate(default_naive(override.modified_start))
        return ruleset


class MyEventOccurrenceOverride(models.Model):
    start = models.DateTimeField()  # must match targeted repetition exactly
    # new start, leave blank to cancel
    modified_start = models.DateTimeField(blank=True, null=True)  

Note that start times must match exactly, so if the MyEventOccurrence start is changed, any previously-matching overrides will no longer be applied.

Use tox (https://pypi.python.org/pypi/tox):

> pip install tox
> cd path-to/django-eventtools
> tox