pycqs 1.0.0

Python Command Query Segregation (CQS) utilities

pycqs

Command Query Segregation (CQS) utilities for Python.

Provides the CommandBus and QueryBus classes.

Requirements

Python 3.10 or above.

Installation

You can use pip to install pycqs with e.g.:

pip install pycqs

Usage

• Using the CommandBus.

import asyncio
from dataclasses import dataclass

from pycqs import (
    Command,
    CommandBus,
    CommandHandler,
)


# Create the command
@dataclass
class HelloWorldCommand(Command):
    name: str


# Create the command handler
class HelloWorldCommandHandler(
    CommandHandler[HelloWorldCommand],
):
    async def execute(
        self,
        command: HelloWorldCommand,
    ) -> None:
        print(f'Hello World, {command.name}')


async def main() -> None:
    # Initialize the command bus
    command_bus = CommandBus()
    command_bus.register_handler(
        HelloWorldCommand,
        HelloWorldCommandHandler(),
    )

    # Execute a command
    command = HelloWorldCommand('cqs')
    await command_bus.execute(command)


if __name__ == '__main__':
    asyncio.run(main())

More usage examples on tests.

• Using the QueryBus.

import asyncio
from dataclasses import dataclass

from pycqs import (
    Query,
    QueryBus,
    QueryHandler,
    QueryResult,
)


# Create the query
@dataclass
class HelloWorldQuery(Query):
    name: str


# Create the query result
@dataclass
class HelloWorldQueryResult(QueryResult):
    message: str


# Create the query handler
class HelloWorldQueryHandler(
    QueryHandler[
        HelloWorldQuery,
        HelloWorldQueryResult,
    ],
):
    async def execute(
        self,
        query: HelloWorldQuery,
    ) -> HelloWorldQueryResult:
        message = f'Hello World, {query.name}'
        return HelloWorldQueryResult(message)


async def main() -> None:
    # Initialize the query bus
    query_bus = QueryBus()
    query_bus.register_handler(
        HelloWorldQuery,
        HelloWorldQueryHandler(),
    )

    # Execute a query
    query = HelloWorldQuery('cqs')
    query_result: HelloWorldQueryResult = await query_bus.execute(query)
    print(query_result.message)


if __name__ == '__main__':
    asyncio.run(main())

More usage examples on tests.

License

MIT