larzsse

Server-Sent Events — server and client. Pure Python, no async, zero deps.

SSE is the simplest way to push a live stream of events from server to browser (or any client) over plain HTTP — one long-lived text/event-stream response. larzsse gives you both ends: a thread-safe Broadcaster that fans events out to every connected client, and a client that connects and iterates parsed events.

from larzsse import Broadcaster, connect

bus = Broadcaster()
server = bus.serve("127.0.0.1", 8080)          # streams at /events
bus.publish("hello", event="greeting")         # every client receives it

for ev in connect("http://127.0.0.1:8080/events"):
    print(ev.event, ev.data)

Why

• Both ends included. A Broadcaster (subscribe/publish/unsubscribe, with keepalives and a built-in threaded server) and a connect() client that parses the stream into Event(event, data, id) objects.
• No async, no dependency. Plain sockets and threads — a lightweight complement to WebSockets (larzws) when you only need server → client push (live dashboards, progress, notifications, log tailing).
• Correct wire format. format_event/parse_events handle data:/event:/ id:/retry:, multiline data, and comment keepalives — round-trip clean.

Install

pip install larzsse

Usage

from larzsse import Broadcaster, connect, format_event

bus = Broadcaster()
bus.serve("0.0.0.0", 8080, path="/events")
bus.publish("payload", event="update", id="42")
bus.client_count

# embed in your own server: stream a subscribed client's events()
client = bus.subscribe()
for chunk in client.events():     # SSE strings; write to the response
    ...

# client
for ev in connect("http://host/events"):
    ev.event, ev.data, ev.id

Tests

python -m unittest discover -s tests -v   # 13 tests incl. live SSE over HTTP

The Larz stack

One of 30+ pure-Python, zero-dependency libraries at github.com/larz-scripter.

License

MIT © larz-scripter