Python Event Sourcery

A library for event-based systems in Python. For event sourcing, CQRS, and event-driven architectures.

event = EventSourceryIsBorn()

event_store.append(event, stream_id=stream_id)

Under heavy development

Documentation: python-event-sourcery.github.io/python-event-sourcery/

Installation

pip install python-event-sourcery

Easy to setup

Just configure your EventStore instance (or a factory) and call configure_models once. Examples below.

Versatile

Event Sourcery makes no assumptions about your configuration or session management. It's designed to be plugged in into what you already have, without a need to adjust anything. It can be integrated smoothly with thread-scoped SQLAlchemy sessions as well as dependency injection.

NOT opinionated

Although one can easily start with a library, the latter is very customizable and DOES NOT enforce a particular style of using. Also, libraries integrated, i.e. SQLAlchemy and Pydantic are not hardcoded dependencies. They can be replaced with a finite amount of effort.

Use cases & features

Until full documentation is available, you can follow tests

Event Sourcing tests
Snapshots (for Event Sourcing) tests
Event Store - storage for events tests
Outbox pattern tests
Concurrency control with optimistic locking tests

Quick start

The script is complete, it should run as-is provided FastAPI and library with dependencies are installed. See examples/0-fastapi-integration

from typing import Iterator, Literal
from uuid import uuid4

from fastapi import FastAPI, Depends
from sqlalchemy import create_engine
from sqlalchemy.orm import Session, as_declarative

# Import a couple of things from event_sourcery
from event_sourcery import EventStore  # for type annotations
from event_sourcery import (
    configure_models,  # set-up function for library's models
    get_event_store,  # factory function to start quickly
    Event,  # base class for events
)

# Set up your DB and application as you would normally do
engine = create_engine(
    "postgresql://event_sourcery:event_sourcery@localhost:5432/event_sourcery"
)


def db_session() -> Iterator[Session]:
    session = Session(bind=engine)
    try:
        yield session
    finally:
        session.close()


@as_declarative()
class Base:
    pass


app = FastAPI(on_startup=[lambda: Base.metadata.create_all(bind=engine)])

# initialize Event Sourcery models, so they can be handled by SQLAlchemy and e.g. alembic
configure_models(Base)


# Set up factory for event store to be injected into views
def event_store(session: Session = Depends(db_session)) -> EventStore:
    return get_event_store(session)


# Define your event(s) using base-class provided
class CustomerSubscribed(Event):
    plan_id: int
    model: Literal["monthly", "yearly"]


@app.post("/subscription")
def subscribe(
    event_store: EventStore = Depends(event_store),
    session: Session = Depends(db_session),
):
    # Create an event
    event = CustomerSubscribed(plan_id=1, model="yearly")
    # Put it in the event store!
    event_store.append(event, stream_id=uuid4())
    session.commit()

Feature requests / feedback

Anything missing? Create an issue in this repository. Let others upvote

Inspirations

Metadata

Release files for python-event-sourcery 0.5.3a4

For a detailed explanation of source distributions (sdists) and built distributions (wheels), please see the package formats documentation.

Source distribution (sdist)

Source distribution for python-event-sourcery 0.5.3a4
File	Size	Uploaded
python_event_sourcery-0.5.3a4.tar.gz	216.1 kB	Aug 24, 2026	Details

Built distribution (wheel)

Table of built distributions (wheels) for python-event-sourcery 0.5.3a4
File	Interpreter	ABI	Platform	Reset
python_event_sourcery-0.5.3a4-py3-none-any.whl 62.2 kB Aug 24, 2026	Python 3	none	any	Details

Total release size: 278.3 kB

Release files / python_event_sourcery-0.5.3a4.tar.gz

Download URL	python_event_sourcery-0.5.3a4.tar.gz
Size	216.1 kB
Tags	Source
SHA-256 checksum How to use checksums	`557666be107a8803e383ec5bdeb34ad2fb6343ce4d8e992f687ce9c93f93af3c`
BLAKE2b-256 checksum How to use checksums	`dab62d55ddc6d44e8a63fa8780ece6b05e46c78cfaa8fc45d91dff781229f8d4`
Upload date	Aug 24, 2026
Uploaded using Trusted Publishing? What is trusted publishing?	No
Uploaded via	`uv/0.12.5 {"installer":{"name":"uv","version":"0.12.5","subcommand":["publish"]},"python":null,"implementation":{"name":null,"version":null},"distro":{"name":"Ubuntu","version":"24.04","id":"noble","libc":null},"system":{"name":null,"release":null},"cpu":null,"openssl_version":null,"setuptools_version":null,"rustc_version":null,"ci":true}`

Release files / python_event_sourcery-0.5.3a4-py3-none-any.whl

Download URL	python_event_sourcery-0.5.3a4-py3-none-any.whl
Size	62.2 kB
Tags	Python 3
SHA-256 checksum How to use checksums	`cb92bb90a58c362fc3a0be0c8ccc3c6248acacafa44aec462e3893bda978d00a`
BLAKE2b-256 checksum How to use checksums	`d1dbceb6f72e851801a341cdaa318ff2c9b05a5c1d7f791fd49b24082696d7f1`
Upload date	Aug 24, 2026
Uploaded using Trusted Publishing? What is trusted publishing?	No
Uploaded via	`uv/0.12.5 {"installer":{"name":"uv","version":"0.12.5","subcommand":["publish"]},"python":null,"implementation":{"name":null,"version":null},"distro":{"name":"Ubuntu","version":"24.04","id":"noble","libc":null},"system":{"name":null,"release":null},"cpu":null,"openssl_version":null,"setuptools_version":null,"rustc_version":null,"ci":true}`