Migrating from caldav 2.x to 3.x#

v3.0 is mostly backward-compatible with v2.x. Existing code should generally continue to run. New method names and usage patterns exists alongside the old ones. The purpose of this document is to give a primer on the “best current usage practice” as of v3.0. It may be needed to implement some of the changes below before using future major versions like v4 or v5.

Breaking Changes#

Python version#

Python 3.10 or later is now required. Python 3.8 and 3.9 are no longer supported.

caldav.objects import shim removed#

The caldav/objects.py backward-compatibility re-export module has been deleted. If you have:

from caldav.objects import Event, Todo, Calendar   # REMOVED

replace it with:

from caldav import Event, Todo, Calendar           # OK

All public symbols that were in caldav.objects should remain available directly from the caldav namespace

Wildcard import into caldav.* removed#

Earlier a wildcard import from caldav.objects import * was done into the caldav namespace. This has been removed. In normal circumstances, your imports should continue to work - but I cannot give any guarantees that YOUR imports will continue working. If you have any issues, then reach out.

..todo:: how to add a link from “reach out” to the contact page?

Config-file parse errors now raise exceptions#

read_config() used to log and return an empty dict on YAML/JSON parse errors. It now raises ValueError. This means misconfigured files fail loudly rather than silently.

Accessing and editing calendar data#

This is the most significant new API in v3.0, addressing a long-standing ambiguity in how calendar object data was accessed and modified.

The old vobject_instance, icalendar_instance, icalendar_component are now deprecated.

The Problem with the 2.x API#

In 2.x, the properties data, icalendar_instance, and vobject_instance on a CalendarObjectResource all shared a single internal slot. Accessing one representation could silently invalidate another:

# 2.x — silent bug
event = calendar.search(...)[0]
comp = event.icalendar_component       # get a reference
_ = event.data                         # accessing data invalidates comp!
comp["SUMMARY"] = "Updated"
event.save()                           # change is NOT saved

The 3.x Solution: read and edit methods#

v3.0 adds explicit read-only getters that always return copies, and context-manager “borrow” methods that give exclusive, safe write access.

Read-only access (safe at any time, returns a copy):

# Get raw iCalendar string
raw = event.get_data()

# Get a copy of the icalendar.Calendar object — changes are NOT saved
cal_copy = event.get_icalendar_instance()
summary = cal_copy.subcomponents[0]["SUMMARY"]

# Get a copy of the vobject component — changes are NOT saved
vobj_copy = event.get_vobject_instance()
summary = vobj_copy.vevent.summary.value

# Quick access to the inner VEVENT/VTODO/VJOURNAL component
summary = event.component["SUMMARY"]   # component is always a copy

Editing with icalendar (borrowing pattern):

with event.edit_icalendar_instance() as cal:
    for comp in cal.subcomponents:
        if comp.name == "VEVENT":
            comp["SUMMARY"] = "Updated summary"
event.save()

Editing with vobject (borrowing pattern):

with event.edit_vobject_instance() as vobj:
    vobj.vevent.summary.value = "Updated summary"
event.save()

While inside the with block, the borrowed representation is the single source of truth. Attempting to borrow a different representation raises RuntimeError. This means the current pattern is not completely thread-safe as of v3.0 - but an explicit error is often better than updates silently being dropped.

The data representation remains the same:

The interface for the string representation is still the same. Strings are immutable, so the concern above is not relevant for strings. (Of course, the code below will have bad side effects if the event was modified simultaneously by another thread, as well as if the event was modified on the server by another client).

## Get the raw iCalendar string
ical_string = event.data
new_ical_string = modify_ical(ical_string)

# Replace all data from a raw iCalendar string
event.data = new_ical_string
event.save()

Summary of the new data API:

Method / property

Purpose

event.get_data()

Raw iCalendar string, always a copy

event.get_icalendar_instance()

icalendar.Calendar copy, safe for read-only use

event.get_vobject_instance()

vobject component copy, safe for read-only use

event.component

Alias for the inner VEVENT/VTODO/VJOURNAL component (copy)

event.edit_icalendar_instance()

Context manager — exclusive write access via icalendar

event.edit_vobject_instance()

Context manager — exclusive write access via vobject

event.data = "..."

Replace all data from a raw string

New in v3.0#

Async client#

Async operations are often the “best current practice” in the Python world. Now it’s possible also with the CalDAV library.

A new caldav.async_davclient.AsyncDAVClient provides the same API with async/await support. All domain objects (Calendar, Event, Todo, …) work with both the sync and async clients:

from caldav.async_davclient import get_davclient

async def main():
    async with await get_davclient(url="...", username="...",
                                   password="...") as client:
        principal = await client.get_principal()
        calendars = await principal.get_calendars()
        for cal in calendars:
            events = await cal.get_events()

See Async API for more details.

JMAP client (experimental)#

A new caldav.jmap package provides JMAPClient and AsyncJMAPClient for servers implementing RFC 8620 (JMAP Core) and RFC 8984 (JMAP Calendars). The public API may change in minor releases. See JMAP.

Compatibility hints / features parameter#

Server-specific quirks are now encoded in named profiles in caldav/compatibility_hints.py. Pass the profile name via the features parameter to get automatic workarounds:

client = get_davclient(url="https://...", features="nextcloud",
                       username="alice", password="secret")

You can also override individual flags:

client = get_davclient(url="https://...",
                       features={"search.text": {"support": "unsupported"}})

In the config file it’s possible to combine a base profile with overrides in the config file:

my-server:
    caldav_url: https://caldav.example.com/
    caldav_username: alice
    caldav_password: secret
    features:
        base: nextcloud
        search.text: unsupported

See Compatibility for more on the compatibility hints system.

Object UID as .id#

CalendarObjectResource.id is now available as a shortcut for the UID property:

event = calendar.add_event(ical_string)
print(event.id)   # same as event.icalendar_component["UID"]

Other notable changes#

caldav 3.x uses niquests by default for HTTP communication. Niquests is a backward-compatible fork of requests that adds HTTP/2, HTTP/3, and async support. If you need to switch to requests or httpx, see HTTP Library Configuration.

Rate-limit support is now built into the CalDAV library. Pass rate_limit_handle=True to automatically sleep and retry on 429 Too Many Requests / 503 Service Unavailable responses that include a Retry-After header:

client = get_davclient(url="...", rate_limit_handle=True)

This may also be configured:

my-server:
    caldav_url: https://caldav.example.com/
    caldav_username: alice
    caldav_password: secret
    features:
        rate_limit:
            enable: True
            default_sleep: 4
            max_sleep: 120

If the server gives a retry-after-header on 429 or 530 it will be respected, otherwise the default_sleep will be utilized on 429. This happens in a loop, the sleep period will be multiplied with 1.5 on every retry.

The total sleep period will never exceed 120, no matter if retry-after is given or not.

Deprecated in v3.0 (will be removed in v4.0)#

The following emit DeprecationWarning:

  • calendar.date_search() — use calendar.search()

  • client.principals() — use client.search_principals()

  • obj.split_expanded attribute

  • obj.expand_rrule attribute

  • .instance property on calendar objects — use .vobject_instance

  • response.find_objects_and_props() — use response.results

The following are deprecated but do not yet emit warnings:

  • All save_* methods → use add_*

  • All *_by_uid() methods → use get_*_by_uid()

  • principal.calendars() → principal.get_calendars()

  • calendar.events() → calendar.get_events()

  • calendar.todos() → calendar.get_todos()

  • calendar.journals() → calendar.get_journals()

  • calendar.objects_by_sync_token() → calendar.get_objects_by_sync_token()

  • client.principal() → client.get_principal()

  • client.check_dav_support() → client.supports_dav()

  • client.check_cdav_support() → client.supports_caldav()

  • client.check_scheduling_support() → client.supports_scheduling()