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psr.event

PSR-14 (php standard recommendation) port for python 3.5+

This repository holds all interfaces related to PSR-14 (Event Dispatcher).

Note that this is not an Event Dispatcher implementation of its own. It is merely interfaces that describe the components of an Event Dispatcher. See the specification for more details.

Architecture overview

Architecture overview

Installation

pip install psr.event --index-url=https://source.md.land/python/

Usage

If you need an event dispatcher, you can use the interface like this:

import psr.event


class StoppableEvent(psr.event.StoppableEventInterface):  # abstract event
    def __init__(self) -> None:
        self._is_propagation_stopped = False

    def stop_propagation(self) -> None:
        self._is_propagation_stopped = True

    def is_propagation_stopped(self) -> bool:
        return self._is_propagation_stopped


class BeforeOperation(StoppableEvent):
    def __init__(self, context: dict) -> None:
        super().__init__()
        self.context = context


class AfterOperation:
    def __init__(self, context: dict) -> None:
        self.context = context


class Operation:  # just dummy example
    def __init__(self, event_dispatcher: psr.event.EventDispatcherInterface) -> None:
        self._event_dispatcher = event_dispatcher

    def operate(self, context: dict) -> None:
        before_operation_event = BeforeOperation(context=context)
        self._event_dispatcher.dispatch(before_operation_event)

        if before_operation_event.is_propagation_stopped():
            return 

        # do something useful

        self._event_dispatcher.dispatch(AfterOperation(context=context))

You can then pick one of the implementations of the interface to get an event dispatcher.

If you want to implement the interface, you can require this package and implement psr.log.EventDispatcherInterface in your code. Please read the specification text for details.

Take a look for md.event — the first implementation.