Python: Subscribe to channel

• By default, Broadcast and Presence are enabled for all projects.
• Presence is automatically enabled when you attach presence callbacks (on_presence_sync(), on_presence_join(), or on_presence_leave()). If you add presence callbacks to an already joined channel, the channel will automatically resubscribe with presence enabled.
• By default, listening to database changes is disabled for new projects due to database performance and security concerns. You can turn it on by managing Realtime's replication.
• You can receive the "previous" data for updates and deletes by setting the table's REPLICA IDENTITY to FULL (e.g., ALTER TABLE your_table REPLICA IDENTITY FULL;).
• Row level security is not applied to delete statements. When RLS is enabled and replica identity is set to full, only the primary key is sent to clients.

Examples

Listen to broadcast messages

channel = supabase.channel("room1")

def on_subscribe(status, err):
    if status == RealtimeSubscribeStates.SUBSCRIBED:
        asyncio.create_task(channel.send_broadcast(
            "cursor-pos",
            {"x": random.random(), "y": random.random()}
        ))

def handle_broadcast(payload):
    print("Cursor position received!", payload)

await channel.on_broadcast(event="cursor-pos", callback=handle_broadcast).subscribe(on_subscribe)

Listen to presence sync

channel = supabase.channel("room1")

def on_subscribe(status, err):
    if status == RealtimeSubscribeStates.SUBSCRIBED:
        asyncio.create_task(channel.track({"online_at": datetime.datetime.now().isoformat()}))

def handle_presence_sync():
    print("Synced presence state: ", channel.presence.state)

await channel.on_presence_sync(callback=handle_presence_sync).subscribe(on_subscribe)

Listen to presence join

channel = supabase.channel("room1")

def handle_presence_join(key, current_presence, new_presence):
    print("Newly joined presences: ", new_presence)

def on_subscribe(status, err):
    if status == RealtimeSubscribeStates.SUBSCRIBED:
        asyncio.create_task(channel.track({"online_at": datetime.datetime.now().isoformat()}))

await channel.on_presence_join(callback=handle_presence_join).subscribe(on_subscribe)

Listen to presence leave

channel = supabase.channel("room1")

def handle_presence_leave(key, current_presence, left_presence):
    print("Newly left presences: ", left_presence)

def on_subscribe(status, err):
    if status == RealtimeSubscribeStates.SUBSCRIBED:
        asyncio.create_task(channel.track({"online_at": datetime.datetime.now().isoformat()}))
        asyncio.create_task(channel.untrack())

await channel.on_presence_leave(callback=handle_presence_leave).subscribe(on_subscribe)

Listen to all database changes

response = (
    await supabase.channel("room1")
    .on_postgres_changes("*", schema="*", callback=handle_record_updated)
    .subscribe()
)

Listen to a specific table

response = (
    await supabase.channel("room1")
    .on_postgres_changes("*", schema="public", table="countries", callback=handle_record_updated)
    .subscribe()
)

Listen to inserts

response = (
    await supabase.channel("room1")
    .on_postgres_changes("INSERT", schema="public", table="countries", callback=handle_record_inserted)
    .subscribe()
)

Listen to updates

response = (
    await supabase.channel("room1")
    .on_postgres_changes("UPDATE", schema="public", table="countries", callback=handle_record_updated)
    .subscribe()
)

Listen to deletes

response = (
    await supabase.channel("room1")
    .on_postgres_changes("DELETE", schema="public", table="countries", callback=handle_record_deleted)
    .subscribe()
)

Listen to multiple events

response = (
    await supabase.channel("room1")
    .on_postgres_changes("INSERT", schema="public", table="countries", callback=handle_record_inserted)
    .on_postgres_changes("DELETE", schema="public", table="countries", callback=handle_record_deleted)
    .subscribe()
)

Listen to row level changes

response = (
    await supabase.channel("room1")
    .on_postgres_changes("UPDATE", schema="public", table="countries", filter="id=eq.200", callback=handle_record_updated)
    .subscribe()
)