Programming Social Applications

Building a Publisher in Python

Note

The full code for this sample is available at https://github.com/jcleblanc/programming-social-applications/tree/master/chapter_10/pubsubhubbub-publisher-python.

Now that we have looked at a publisher implementation in PHP, let’s explore the same implementation using Python for an alternate vantage point.

For this example, the classes that make up the publisher are stored in a file named publisher.py:

import re import urllib import urllib2 ''' ' Class: Publishing Error ' Description: Custom error class for publishing exceptions ''' class PublishError(Exception): def __init__(self, value): self.value = value def __str__(self): return repr(self.value) ''' ' Class: Publisher ' Description: Provides ability to publish updates for feeds ''' class Publisher: regex_url = re.compile('^https?://') #simple URL string validator #constructor that stores the hub for the publisher def __init__(self, hub): if self.regex_url.match(hub): self.hub = hub else: raise PublishError('Invalid hub URL supplied') #makes request to hub to update feeds def publish(self, feeds): #set the POST string mode post_string = 'hub.mode=publish' #add each feed as a URL in the POST string, unless invalid URL for feed in feeds: if self.regex_url.match(feed): post_string += '&hub.url=%s' % (urllib.quote(feed)) else: raise PublishError('Invalid feed URL supplied: %s' % (feed)) try: #make request to hub file = urllib2.urlopen(self.hub, post_string) return True except (IOError, urllib2.HTTPError), ...