Python-Design-Patterns publish_subscribe
Table of Contents
publish_subscribe Model
Python-Design-Patterns publish_subscribe
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#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
Reference:
http://www.slideshare.net/ishraqabd/publish-subscribe-model-overview-13368808
Author: https://github.com/HanWenfang
"""
class Provider:
def __init__(self):
self.msg_queue = []
self.subscribers = {}
def notify(self, msg):
self.msg_queue.append(msg)
def subscribe(self, msg, subscriber):
self.subscribers.setdefault(msg, []).append(subscriber)
def unsubscribe(self, msg, subscriber):
self.subscribers[msg].remove(subscriber)
def update(self):
for msg in self.msg_queue:
for sub in self.subscribers.get(msg, []):
sub.run(msg)
self.msg_queue = []
class Publisher:
def __init__(self, msg_center):
self.provider = msg_center
def publish(self, msg):
self.provider.notify(msg)
class Subscriber:
def __init__(self, name, msg_center):
self.name = name
self.provider = msg_center
def subscribe(self, msg):
self.provider.subscribe(msg, self)
def unsubscribe(self, msg):
self.provider.unsubscribe(msg, self)
def run(self, msg):
print("{} got {}".format(self.name, msg))
def main():
message_center = Provider()
fftv = Publisher(message_center)
jim = Subscriber("jim", message_center)
jim.subscribe("cartoon")
jack = Subscriber("jack", message_center)
jack.subscribe("music")
gee = Subscriber("gee", message_center)
gee.subscribe("movie")
vani = Subscriber("vani", message_center)
vani.subscribe("movie")
vani.unsubscribe("movie")
fftv.publish("cartoon")
fftv.publish("music")
fftv.publish("ads")
fftv.publish("movie")
fftv.publish("cartoon")
fftv.publish("cartoon")
fftv.publish("movie")
fftv.publish("blank")
message_center.update()
if __name__ == "__main__":
main()
### OUTPUT ###
# jim got cartoon
# jack got music
# gee got movie
# jim got cartoon
# jim got cartoon
# gee got movie
publish_subscribe.py
publish_subscribe Test
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#!/usr/bin/env python
# -*- coding: utf-8 -*-
import unittest
from behavioral.publish_subscribe import Provider, Publisher, Subscriber
try:
from unittest.mock import patch, call
except ImportError:
from mock import patch, call
class TestProvider(unittest.TestCase):
"""
Integration tests ~ provider class with as little mocking as possible.
"""
def test_subscriber_shall_be_attachable_to_subscriptions(cls):
subscription = 'sub msg'
pro = Provider()
cls.assertEqual(len(pro.subscribers), 0)
sub = Subscriber('sub name', pro)
sub.subscribe(subscription)
cls.assertEqual(len(pro.subscribers[subscription]), 1)
def test_subscriber_shall_be_detachable_from_subscriptions(cls):
subscription = 'sub msg'
pro = Provider()
sub = Subscriber('sub name', pro)
sub.subscribe(subscription)
cls.assertEqual(len(pro.subscribers[subscription]), 1)
sub.unsubscribe(subscription)
cls.assertEqual(len(pro.subscribers[subscription]), 0)
def test_publisher_shall_append_subscription_message_to_queue(cls):
""" msg_queue ~ Provider.notify(msg) ~ Publisher.publish(msg) """
expected_msg = 'expected msg'
pro = Provider()
pub = Publisher(pro)
Subscriber('sub name', pro)
cls.assertEqual(len(pro.msg_queue), 0)
pub.publish(expected_msg)
cls.assertEqual(len(pro.msg_queue), 1)
cls.assertEqual(pro.msg_queue[0], expected_msg)
def test_provider_shall_update_affected_subscribers_with_published_subscription(cls):
pro = Provider()
pub = Publisher(pro)
sub1 = Subscriber('sub 1 name', pro)
sub1.subscribe('sub 1 msg 1')
sub1.subscribe('sub 1 msg 2')
sub2 = Subscriber('sub 2 name', pro)
sub2.subscribe('sub 2 msg 1')
sub2.subscribe('sub 2 msg 2')
with patch.object(sub1, 'run') as mock_subscriber1_run, patch.object(sub2, 'run') as mock_subscriber2_run:
pro.update()
cls.assertEqual(mock_subscriber1_run.call_count, 0)
cls.assertEqual(mock_subscriber2_run.call_count, 0)
pub.publish('sub 1 msg 1')
pub.publish('sub 1 msg 2')
pub.publish('sub 2 msg 1')
pub.publish('sub 2 msg 2')
with patch.object(sub1, 'run') as mock_subscriber1_run, patch.object(sub2, 'run') as mock_subscriber2_run:
pro.update()
expected_sub1_calls = [call('sub 1 msg 1'), call('sub 1 msg 2')]
mock_subscriber1_run.assert_has_calls(expected_sub1_calls)
expected_sub2_calls = [call('sub 2 msg 1'), call('sub 2 msg 2')]
mock_subscriber2_run.assert_has_calls(expected_sub2_calls)
test_publish_subscribe.py
