emitix is a lightweight event bus for dispatching named events to Python handlers inside an application. Install it with pip install emitix, register a function with @emitix.on("user.created"), and send an event with emitix.emit("user.created", "Ada"). The PyPI listing specifies Python 3.9 or newer; its release and compatibility metadata can change, so check the emitix project page on PyPI before installing.
What does an event bus do?
An event bus lets one part of an application announce that something happened without calling each interested component directly. A publisher emits a named event, such as user.created, and registered handlers respond to it. This can help separate responsibilities within a Python application—for example, letting several functions react to a newly created user.
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emitix documents this in-process event-bus pattern. Its project description calls it a “Lightweight event bus for Python applications. No dependencies, fully typed, works with both sync and async code.” The project documentation describes dispatch and subscriptions, not durable event storage, cross-process delivery, retries, or message-broker integrations. Those capabilities are not established by the project sources cited here.
How do you install and use emitix?
The shortest path is to install the package, subscribe a handler, then emit the matching event. The examples below use the module-level API, which works with a shared bus.
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- Install the package in your environment:
pip install emitix. - Import it and register a handler with
@emitix.on("user.created"). - Dispatch the event with
emitix.emit("user.created", "Ada").
import emitix
@emitix.on("user.created")
def greet(name):
return f"Welcome, {name}!"
results = emitix.emit("user.created", "Ada")
print(results)Arguments passed to emit are passed to matching handlers, and the call returns handler results. Keep the event name consistent between subscription and dispatch; a handler registered for a different name will not match this exact event.
When should you use a separate EventBus?
The module-level helpers use a shared bus, which is convenient when components in an application should subscribe to the same event stream. If you need isolated subscriptions—for example, to keep unrelated application components or tests from sharing handlers—create an EventBus instance and use that instance’s methods instead.
from emitix import EventBus
bus = EventBus()
@bus.on("user.created")
def record_user(name):
return name
results = bus.emit("user.created", "Ada")The module-level bus and an explicitly created bus provide the same basic publish-and-subscribe model, but subscriptions on a separate instance are scoped to that instance.
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Register once or repeatedly
Use on to register a handler, including as a decorator. Use once when a handler should be registered for one invocation. The API also provides off to remove one handler or all handlers for an event, and clear to remove every subscription.
Match a family of event names
Wildcard subscriptions accept shell-style patterns. For example, user.* can match event names in the user family. Set pass_event=True when registering the handler if it also needs the actual matching event name; this is useful when one function handles several related event names.
@emitix.on("user.*", pass_event=True)
def log_user_event(event_name, *args):
print(event_name, args)
emitix.emit("user.created", "Ada")Set the order handlers run
Handler priority controls execution order: higher-priority handlers run first. Handlers with the same priority retain their registration order. This is useful when one handler must run before another, but ordering does not provide isolation: an exception in an earlier handler can prevent later handlers from running.
How do you handle asynchronous events?
Use emit_async when matching subscriptions include async handlers. The README says it awaits async handlers and invokes regular handlers normally, sequentially in priority order. Plain emit raises TypeError if a matching async handler is registered.
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import emitix
@emitix.on("user.created")
async def send_welcome_email(name):
return f"Queued a welcome for {name}"
results = await emitix.emit_async("user.created", "Ada")The example must run in an async context, such as inside an async def function. Because dispatch is documented as sequential, do not assume that async handlers run concurrently.
What happens if a handler fails?
An exception raised by a handler propagates to the caller and stops the remaining handlers for that dispatch. If later handlers perform important work, account for that behavior in the calling code: catch exceptions around dispatch where appropriate, or design handlers so a failure cannot silently prevent essential downstream actions. The documented behavior does not describe automatic retries or per-handler exception isolation.
The project README describes its methods as thread-safe. That is a concurrency-safety statement for the documented methods, not a claim that dispatch is durable or distributed across processes.
Is emitix the right fit for your application?
The PyPI listing identifies version 0.1.1, uploaded October 1, 2026, as the latest release in its metadata snapshot, marks the project with an Alpha development classifier, and specifies an MIT license and Python 3.9 or newer. Check PyPI for current release information. Alpha status is a reason to assess project maturity against your own reliability, support, and maintenance requirements.
Quick Recap
- Consider emitix when you want named in-process events, sync and async handler support, wildcard subscriptions, and priority-based ordering.
- Do not treat it as a documented substitute for a persistent queue or broker-backed system if your requirements include storage, cross-process delivery, or retries.
- No performance benchmarks or adoption statistics are established by the project sources cited here, so avoid choosing it on assumed speed or popularity.
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