zulip/templates/zerver/api/real-time-events.md

Real-time events API

Zulip's real-time events API lets you write software that reacts immediately to events happening in Zulip. This API is what powers the real-time updates in the Zulip web and mobile apps. As a result, the events available via this API cover all changes to data displayed in the Zulip product, from new messages to stream descriptions to emoji reactions to changes in user or organization-level settings.

Using the events API

The simplest way to use Zulip's real-time events API is by using call_on_each_event from our Python bindings. You just need to write a Python function (in the examples below, the lambdas) and pass it into call_on_each_event; your function will be called whenever a new event matching the specific event_type and/or narrow arguments occurs in Zulip.

call_on_each_event takes care of all the potentially tricky details of long-polling, error handling, exponential backoff in retries, etc. It's cousin, call_on_each_message, provides an even simpler interface for processing Zulip messages.

More complex applications (like a Zulip terminal client) may need to instead use the raw register and events endpoints.

Usage examples

{start_tabs} {tab|python}

#!/usr/bin/env python

import sys
import zulip

# Pass the path to your zuliprc file here.
client = zulip.Client(config_file="~/zuliprc")

# Print every message the current user would receive
# This is a blocking call that will run forever
client.call_on_each_message(lambda msg: sys.stdout.write(str(msg) + "\n"))

# Print every event relevant to the user
# This is a blocking call that will run forever
client.call_on_each_event(lambda event: sys.stdout.write(str(event) + "\n"))

{end_tabs}

Arguments

You may also pass in the following keyword arguments to call_on_each_event:

{generate_api_arguments_table|zulip.yaml|/real-time:post}

See the GET /events documentation for more details on the format of individual events.