如何在Python中使用onDisconnect？Pyrebase基于Rest API能否调用该方法？

Great question—let’s break this down clearly into the two parts you asked about.

Can you use onDisconnect() via Firebase's REST API? #

Short answer: No, you can’t.

Firebase’s onDisconnect() functionality relies on a persistent, stateful connection between the client and the Realtime Database server. The REST API, however, is stateless—it uses short-lived HTTP requests that don’t maintain an open connection. There’s no way to register a "disconnect" handler through REST because the server has no way to track when the client goes offline after the request completes.

If you need offline-triggered actions with REST, you’d have to build a workaround: for example, having your client send periodic "heartbeat" updates to a database node, then using a Cloud Function or separate script to check for stale heartbeats and mark the client as offline. This isn’t as reliable or real-time as native onDisconnect(), but it’s the closest alternative for REST-based workflows.

How to use onDisconnect() in Python #

Pyrebase (which wraps Firebase’s REST API) doesn’t support onDisconnect() for the same reason REST doesn’t—it can’t maintain the persistent connection needed to trigger the handler. Instead, you’ll want to use the official Firebase Admin SDK for Python, which supports the full Realtime Database feature set, including onDisconnect().

Here’s a step-by-step implementation:

1. Install the Firebase Admin SDK #

First, install the package via pip:

pip install firebase-admin

2. Initialize the SDK #

You’ll need a service account key file from your Firebase project (download it from the Firebase Console > Project Settings > Service Accounts):

import firebase_admin
from firebase_admin import credentials
from firebase_admin import db

# Initialize the app with your service account
cred = credentials.Certificate("path/to/your-service-account-key.json")
firebase_admin.initialize_app(cred, {
    "databaseURL": "https://your-project-id.firebaseio.com/"
})

3. Use on_disconnect() to define offline actions #

Once initialized, you can attach on_disconnect() handlers to any database reference. These actions will execute automatically when the client’s connection to Firebase drops (whether intentionally or unexpectedly):

# Get a reference to the user's status node
user_status_ref = db.reference("users/john_doe/status")

# Set the user's status to "offline" when disconnected
user_status_ref.on_disconnect().set("offline")

# Optional: Set an initial "online" status
user_status_ref.set("online")

# You can also delete a node on disconnect, or update multiple values
# user_status_ref.on_disconnect().delete()
# user_status_ref.on_disconnect().update({"status": "offline", "last_seen": db.ServerValue.TIMESTAMP})

Key Notes #

• The Admin SDK maintains a persistent connection to Firebase, so the on_disconnect() handler is registered directly with the server and will trigger reliably.
• If you need to cancel a pending on_disconnect() action, call cancel() on the handler:

  disconnect_handler = user_status_ref.on_disconnect().set("offline")
  disconnect_handler.cancel()
  

内容的提问来源于stack exchange，提问作者beratuslu