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emitix is a lightweight event bus for Python: register functions to respond to named events, then dispatch those events with data. Install it with pip install emitix. Its module-level API uses a shared bus; create an EventBus instance when you need an independent set of subscriptions.
What an event bus does—and what emitix is
An event bus lets one part of an application announce that something happened without directly calling every function that may respond. For example, account-creation code can emit user.created; separate handlers can then send a notification, update an in-memory view, or perform another task.
The emitix project describes the package as a “Lightweight event bus for Python applications. No dependencies, fully typed, works with both sync and async code.” That is the project’s description on PyPI. The documented model is dispatch within a Python application. The project material does not document durable event storage, cross-process delivery, retries, or message-broker integrations.
Install emitix and register your first handler
PyPI lists Python 3.9 or later as the minimum. Install the package in the environment used by your application:
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pip install emitixThen register a function and emit the matching event:
import emitix
@emitix.on("user.created")
def welcome_user(name):
print(f"Welcome, {name}!")
results = emitix.emit("user.created", "Ada")
Calling emit invokes matching handlers with the supplied positional and keyword arguments. Its return value contains the handlers’ results. The decorator form of on registers the function while leaving it available to call directly as well.
Choose the shared bus or a separate EventBus
The module-level functions, such as emitix.on and emitix.emit, operate on a shared bus. This is convenient when different modules in one application need to publish and subscribe without passing a bus object around.
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Use an EventBus instance when subscriptions should be isolated—for example, when separate components or tests need independent event namespaces:
from emitix import EventBus
bus = EventBus()
@bus.on("user.created")
def record_user(name):
print(f"Recorded {name}")
bus.emit("user.created", "Ada")
Register one-time handlers, patterns, and priorities
Run a handler once
Use once for a callback that should be invoked for a single matching event rather than every dispatch:
@emitix.once("startup.ready")
def announce_ready():
print("Ready")Subscribe to a wildcard pattern
Subscriptions can use shell-style patterns such as user.* to match event names in that family. Set pass_event=True if the handler also needs the actual name that matched:
@emitix.on("user.*", pass_event=True)
def audit_user_event(event_name, user_id):
print(event_name, user_id)
emitix.emit("user.created", 42)With pass_event=True, the matching event name is passed to the handler along with the event arguments; define the handler’s parameters accordingly.
Set handler order with priorities
Higher-priority handlers run before lower-priority handlers. Handlers with the same priority retain registration order. Use priorities when a particular handler must run earlier, but keep in mind that an exception can prevent later handlers from running.
Handle asynchronous events with emit_async
Use emit_async when a matching subscription includes an async handler. It awaits async handlers and also invokes regular handlers. The README documents sequential execution in priority order; it does not describe parallel handler execution.
import emitix
@emitix.on("report.ready")
async def save_report(report):
await store_report(report)
await emitix.emit_async("report.ready", report)Call emit_async from an async context. If a matching async handler is registered, plain emit raises TypeError; it does not automatically await that handler.
Remove handlers and manage failures
Unsubscribe or clear registrations
Use off to remove a handler, or to remove all handlers for an event. Use clear to remove every subscription on the relevant bus. The project README says these methods are thread-safe.
Account for exceptions
If a handler raises an exception, it propagates to the caller and stops the remaining handlers for that dispatch. If later handlers perform important side effects, make the earlier handler’s failure behavior part of your design—such as handling recoverable errors inside that handler or deciding whether the caller should catch the exception.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Check emitix’s current status before adopting it
As of October 1, 2026, PyPI lists version 0.1.1, uploaded on that date, with the Alpha development classifier, MIT license, Python 3.9+ support, and no runtime dependencies stated in the project description. These are release-page details that may change; consult the PyPI project page for current metadata before relying on them. Alpha status is a reason to evaluate the package’s maturity against your project’s stability requirements.
The package is a fit to investigate when you want in-application event dispatch with sync and async handlers, wildcard subscriptions, and explicit ordering. If your requirement includes persistence, delivery across processes, retries, or a broker, those capabilities are not established by the project documentation; assess a system that documents the guarantees you need.
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