Recurring ICal events for Python

ICal has some complexity to it: Events can be repeated, removed from the feed and edited later on. This tool takes care of these circumstances.

Let's put our expertise together and build a tool that can solve this!

• day light saving time (DONE)
• recurring events (DONE)
• recurring events with edits (DONE)
• recurring events where events are omitted (DONE)
• recurring events events where the edit took place later (DONE)
• normal events (DONE)
• recurrence of dates but not hours, minutes, and smaller (DONE)
• endless recurrence (DONE)
• ending recurrence (DONE)
• events with start date and no end date (DONE)
• events with start as date and start as datetime (DONE)
• RRULE (DONE)
• RDATE (DONE)
• DURATION (DONE)
• EXDATE (DONE)
• X-WR-TIMEZONE compatibilty (DONE)

Not included:

• EXRULE (deprecated), see 8.3.2. Properties Registry

Installation

pip install recurring-ical-events

Example

import icalendar
import recurring_ical_events
import urllib.request

start_date = (2019, 3, 5)
end_date =   (2019, 4, 1)
url = "http://tinyurl.com/y24m3r8f"

ical_string = urllib.request.urlopen(url).read()
calendar = icalendar.Calendar.from_ical(ical_string)
events = recurring_ical_events.of(calendar).between(start_date, end_date)
for event in events:
    start = event["DTSTART"].dt
    duration = event["DTEND"].dt - event["DTSTART"].dt
    print("start {} duration {}".format(start, duration))

Output:

start 2019-03-18 04:00:00+01:00 duration 1:00:00
start 2019-03-20 04:00:00+01:00 duration 1:00:00
start 2019-03-19 04:00:00+01:00 duration 1:00:00
start 2019-03-07 02:00:00+01:00 duration 1:00:00
start 2019-03-08 01:00:00+01:00 duration 2:00:00
start 2019-03-09 03:00:00+01:00 duration 0:30:00
start 2019-03-10 duration 1 day, 0:00:00

Usage

The icalendar module is responsible for parsing and converting calendars. The recurring_ical_events module uses such a calendar and creates all repetitions of its events within a time span.

To import this module, write

import recurring_ical_events

There are several methods you can use to unfold repeating events, such as at(a_time) and between(a_start, an_end).

at(a_date)

You can get all events which take place at a_date. A date can be a year, e.g. 2023, a month of a year e.g. January in 2023 (2023, 1), a day of a certain month e.g. (2023, 1, 1), an hour e.g. (2023, 1, 1, 0), a minute e.g. (2023, 1, 1, 0, 0), or second as well as a datetime.date object and datetime.datetime.

The start and end are inclusive. As an example: if an event is longer than one day it is still included if it takes place at a_date.

a_date =  2023   # a year
a_date = (2023,) # a year
a_date = (2023, 1) # January in 2023
a_date = (2023, 1, 1) # the 1st of January in 2023
a_date = "20230101"   # the 1st of January in 2023
a_date = (2023, 1, 1, 0) # the first hour of the year 2023
a_date = (2023, 1, 1, 0, 0) # the first minute in 2023
a_date = datetime.date(2023) # the first day in 2023
a_date = datetime.date(2023, 1, 1) # the first day in 2023
a_date = datetime.datetime.now() # this exact second

events = recurring_ical_events.of(an_icalendar_object).at(a_date)

The resulting events are a list of icalendar events, see below.

between(start, end)

between(start, end) returns all events happening between a start and an end time. Both arguments can be datetime.datetime, datetime.date, tuples of numbers passed as arguments to datetime.datetime or strings in the form of %Y%m%d (yyyymmdd) and %Y%m%dT%H%M%SZ (yyyymmddThhmmssZ). For examples, see at(a_date) above.

events = recurring_ical_events.of(an_icalendar_object).between(start, end)

The resulting events are in a list, see below.

events as list

The result of both between(start, end) and at(a_date) is a list of icalendar events. By default, all attributes of the event with repetitions are copied, like UID and SUMMARY. However, these attributes may differ from the source event:

• DTSTART which is the start of the event instance. (always present)
• DTEND which is the end of the event instance. (always present)
• RDATE, EXDATE, RRULE are the rules to create event repetitions. They are not included in repeated events, see Issue 23. To change this, use of(calendar, keep_recurrence_attributes=True).

Speed

If you use between() or at() several times, it is faster to re-use the object coming from of().

rcalendar = recurring_ical_events.of(an_icalendar_object)
events_of_day_1 = rcalendar.at(day_1)
events_of_day_2 = rcalendar.at(day_2)
events_of_day_3 = rcalendar.at(day_3)
# ...

Version Fixing

If you use this library in your code, you may want to make sure that updates can be received but they do not break your code. The version numbers are handeled this way: a.b.c example: 0.1.12

• c is changed for each minor bug fix.
• b is changed whenever new features are added.
• a is changed when the interface or major assumptions change that may break your code.

So, I recommend to version-fix this library to stay with the same a while b and c can change.

Support

This library is part of the Open Web Calendar Collective. We accept donations to sustain our work, once or regular. Open Collective makes it easy for you to give and for us to receive. Consider donating money to open-source as everyone benefits.

Development

1. Optional: Install virtualenv and Python3 and create a virtual environment.

   virtualenv -p python3 ENV
   source ENV/bin/activate

2. Install the packages.

   pip install -r requirements.txt -r test-requirements.txt

3. Run the tests

   pytest

New Releases

To release new versions,

1. edit the Changelog Section

2. edit setup.py, the __version__ variable

3. create a commit and push it

4. Wait for GitHub Actions to finish the build.

5. run

   python3 setup.py tag_and_deploy

6. notify the issues about their release

Testing

This project's development is driven by tests. Tests assure a consistent interface and less knowledge lost over time. If you like to change the code, tests help that nothing breaks in the future. They are required in that sense. Example code and ics files can be transferred into tests and speed up fixing bugs.

You can view the tests in the test folder. If you have a calendar ICS file for which this library does not generate the desired output, you can add it to the test/calendars folder and write tests for what you expect. If you like, open an issue first, e.g. to discuss the changes and how to go about it.

Changelog

• v1.0.3b
  • Remove syntax anomalies in README.
  • Switch to GitHub actions because GitLab decided to remove support.
• v1.0.2b
  • Add support for X-WR-TIMEZONE calendars which contain events without an explicit time zone, see Issue 86.
• v1.0.1b
  • Add support for zoneinfo.ZoneInfo time zones, see Issue 57.
  • Migrate from Travis CI to Gitlab CI.
  • Add code coverage on Gitlab.
• v1.0.0b
  • Remove Python 2 support, see Issue 64.
  • Remove support for Python 3.5 and 3.6.
  • Note: These deprecated Python versions may still work. We just do not claim they do.
  • X-WR-TIMEZONE support, see Issue 71.
• v0.2.4b
  • Events with a duration of 0 seconds are correctly returned.
  • between() and at() take the same kind of arguments. These arguments are documented.
• v0.2.3b
  • between() and at() allow arguments with time zones now when calendar events do not have time zones, reported in Issue 61 and Issue 52.
• v0.2.2b
  • Check that at() does not return an event starting at the next day, see Issue 44.
• v0.2.1b
  • Check that recurring events are removed if they are modified to leave the requested time span, see Issue 62.
• v0.2.0b
  • Add ability to keep the recurrence attributes (RRULE, RDATE, EXDATE) on the event copies instead of stripping them. See Pull Request 54.
• v0.1.21b
  • Fix issue with repetitions over DST boundary. See Issue 48.
• v0.1.20b
  • Fix handling of modified recurrences with lower sequence number than their base event Pull Request 45
• v0.1.19b
  • Benchmark using @mrx23dot's script and speed up recurrence calculation by factor 4, see Issue 42.
• v0.1.18b
  • Handle Issue 28 so that EXDATEs match as expected.
  • Handle Issue 27 so that parsing some rrule UNTIL values does not crash.
• v0.1.17b
  • Handle Issue 28 where passed arguments lead to errors where it is expected to work.
• v0.1.16b
  • Events with an empty RRULE are handled like events without an RRULE.
  • Remove fixed dependency versions, see Issue 14
• v0.1.15b
  • Repeated events also include subcomponents. Issue 6
• v0.1.14b
  • Fix compatibility issue 20: EXDATEs of different time zones are now supported.
• v0.1.13b
  • Remove attributes RDATE, EXDATE, RRULE from repeated events Issue 23
  • Use vDDDTypes instead of explicit date/datetime type Pull Request 19
  • Start Changelog

Libraries Used

• python-dateutil - to compute the recurrences of events using rrule
• icalendar - the library used to parse ICS files
• pytz - for timezones
• x-wr-timezone for handling the non-standard X-WR-TIMEZONE property.

Related Projects

• icalevents - another library for roughly the same use-case
• Open Web Calendar - a web calendar to embed into websites which uses this library
• icspy - to create your own calendar events

Media

Nicco Kunzmann talked about this library at the FOSSASIA 2022 Summit:

Research

• RFC 5545
• RFC 7986 -- an update to RFC 5545. It does not change any properties useful for scheduling events.
• Stackoverflow question this is created for
• https://github.com/oberron/annum
  • https://stackoverflow.com/questions/28829261/python-ical-get-events-for-a-day-including-recurring-ones#28829401
• https://stackoverflow.com/questions/20268204/ical-get-date-from-recurring-event-by-rrule-and-dtstart
• collective/icalendar#162
• https://stackoverflow.com/questions/46471852/ical-parsing-reoccuring-events-in-python
• RDATE https://stackoverflow.com/a/46709850/1320237
  • https://tools.ietf.org/html/rfc5545#section-3.8.5.2