Hey there, let's break down why you're running into unknown errors while using the caldav library with Yandex's CalDAV service. Even without the exact error trace, here are the most likely issues and fixes based on your code snippet:

1. App-Specific Password Requirement #

Yandex enforces app-specific passwords for third-party apps accessing CalDAV if you have two-factor authentication (2FA) enabled on your account. Your regular account password won't work here. To fix this:

• Head to your Yandex account's security settings
• Generate a dedicated app password for CalDAV access
• Replace your regular password in the DAVClient initialization with this app-specific password

2. Incorrect CalDAV URL/Principal Path #

Your current URL (https://caldav.yandex.ru/) might be too generic. Yandex sometimes expects a specific principal path tied to your username. Try updating the client URL to:

client = caldav.DAVClient(
    url=f'https://caldav.yandex.ru/principals/{your_username}/',
    username=your_username,
    password=your_app_password
)

Also, add a check to confirm the principal is being found correctly:

my_principal = client.principal()
if not my_principal:
    print("Failed to locate principal - verify your URL and credentials")

3. Strict iCalendar Format Enforcement #

Yandex's CalDAV service can be picky about iCalendar formatting. Let's adjust your vcal content to meet its expectations:

• Use a unique UID (static UIDs like 1234567890 can cause conflicts)
• Add an ORGANIZER field linked to your Yandex email
• Ensure all timestamps follow the strict ISO 8601 format

Here's a modified version:

import uuid

your_username = "your-yandex-username"
vcal = f"""BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Example Corp.//CalDAV Client//EN
BEGIN:VEVENT
UID:{uuid.uuid4()}
DTSTAMP:20100510T182145Z
DTSTART:20100512T170000Z
DTEND:20100512T180000Z
ORGANIZER:mailto:{your_username}@yandex.ru
SUMMARY:This is an event
END:VEVENT
END:VCALENDAR"""

4. Capture Exact Error Details #

Since you're seeing an "unknown error", wrapping your code in a try-except block will reveal the exact server response and exception type—this is the fastest way to diagnose the issue:

import caldav
from caldav.lib.error import DavError
import uuid

try:
    client = caldav.DAVClient(
        url='https://caldav.yandex.ru/',
        username='your-yandex-username',
        password='your-app-password'
    )
    my_principal = client.principal()
    print(f"Successfully loaded principal: {my_principal}")
    
    calendars = my_principal.calendars()
    print(f"Found {len(calendars)} available calendars")
    
    if calendars:
        vcal = f"""BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Example Corp.//CalDAV Client//EN
BEGIN:VEVENT
UID:{uuid.uuid4()}
DTSTAMP:20100510T182145Z
DTSTART:20100512T170000Z
DTEND:20100512T180000Z
ORGANIZER:mailto:your-yandex-username@yandex.ru
SUMMARY:This is an event
END:VEVENT
END:VCALENDAR"""
        saved_event = calendars[0].save_event(vcal)
        print(f"Event saved successfully: {saved_event.url}")
except DavError as e:
    print(f"CalDAV Server Error: {e}")
    print(f"Server Response: {e.response}")
except Exception as e:
    print(f"Unexpected Error: {type(e).__name__} - {str(e)}")

Running this will give you specific error codes (like 401 Unauthorized, 404 Not Found) and server messages that will point you directly to the problem.

5. Update Dependencies or SSL Configuration #

The caldav library relies on requests for HTTP calls. Outdated versions can cause SSL/TLS issues with Yandex's servers. First, update your dependencies:

pip install --upgrade caldav requests

If SSL issues persist, you can explicitly pass an SSL context to the client:

import ssl

context = ssl.create_default_context()
client = caldav.DAVClient(
    url='https://caldav.yandex.ru/',
    username='your-username',
    password='your-app-password',
    ssl_context=context
)

内容的提问来源于stack exchange，提问作者Эйнберт Альштейн