Python mediator bus microframework for CQRS + ES
Project description
python-mediator
Elastic and extensible asyncio CQRS + ES python microframework. Compatible with recent python versions: 3.7, 3.8, 3.9, pypy3.
Corresponds to clean architecture patterns, ideal for command/query segregation scenarios and event-driven design approaches. No external dependencies - uses only standard libraries.
Key features:
- automatic function or method handler inspection - proper action (command/query/event) to handler matching is fully automatic and based on python type hints (annotations) by default
- configurable middleware (operator) stack - handler call flow can be extended easily with i.e. data mapping, special exception handling or extra logging
- configurable extra parameters injection
- elastic and extensible - custom behaviours and custom transport backends can be adapted with small effort
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A command/query handling example
from dataclasses import dataclass
from mediator.request import LocalRequestBus
bus = LocalRequestBus()
@dataclass
class PrintMessageCommand:
message: str
@bus.register
async def command_handler(event: PrintMessageCommand):
print(f"print message: {event.message}")
return event.message
@dataclass
class DataQuery:
id: int
@bus.register
async def query_handler(query: DataQuery):
print(f"data query: {query.id}")
return {"id": query.id, "data": "test"}
async def main():
printed_message = await bus.execute(PrintMessageCommand(message="test"))
assert printed_message == "test"
data = await bus.execute(DataQuery(id=1))
assert data == {"id": 1, "data": "test"}
# -- output --
# print message: test
# data query: 1
More advanced example available in tests/example/test_request_advanced.py for reference.
An event handling example
from dataclasses import dataclass
from mediator.event import LocalEventBus
bus = LocalEventBus()
@dataclass
class MessageEvent:
message: str
@bus.register
async def first_handler(event: MessageEvent):
print(f"first handler: {event.message}")
@bus.register
async def second_handler(event: MessageEvent):
print(f"second handler: {event.message}")
async def main():
await bus.publish(MessageEvent(message="test"))
# -- output --
# first handler: test
# second handler: test
More advanced example available in tests/example/test_event_advanced.py for reference.
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