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

Installation

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.

Setup

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)

Usage

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.

Queryset filtering

Event and Occurrence querysets can be filtered, but note that a from_date filtered queryset may contain false positives because it's not possible to tell for sure if a event will happen after a certain date without evaluating repetition rules, meaning it can't be part of a database query. If you need a queryset filtered exactly, pass exact=True - this will filter the queryset by id, based on generated occurrences. Be careful with this option though 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)

Note to_date filtering is always accurate, because the query only needs to consider the event's first occurrence.

Sorting querysets

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.

Custom repeat intervals

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.

Occurrence cancellations or modifications

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.

Running tests

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

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