The Evolution of Finger: cleaning up the finger code

  1. Introduction
  2. Write Readable Code

Introduction

This is the third part of the Twisted tutorial Twisted from Scratch, or The Evolution of Finger.

In this section of the tutorial, we'll clean up our code so that it is closer to a readable and extensible style.

Write Readable Code

The last version of the application had a lot of hacks. We avoided sub-classing, didn't support things like user listings over the web, and removed all blank lines -- all in the interest of code which is shorter. Here we take a step back, subclass what is more naturally a subclass, make things which should take multiple lines take them, etc. This shows a much better style of developing Twisted applications, though the hacks in the previous stages are sometimes used in throw-away prototypes.

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# Do everything properly from twisted.application import internet, service from twisted.internet import protocol, reactor, defer from twisted.words.protocols import irc from twisted.protocols import basic from twisted.web import resource, server, static, xmlrpc import cgi def catchError(err): return "Internal error in server" class FingerProtocol(basic.LineReceiver): def lineReceived(self, user): d = self.factory.getUser(user) d.addErrback(catchError) def writeValue(value): self.transport.write(value+'\r\n') self.transport.loseConnection() d.addCallback(writeValue) class IRCReplyBot(irc.IRCClient): def connectionMade(self): self.nickname = self.factory.nickname irc.IRCClient.connectionMade(self) def privmsg(self, user, channel, msg): user = user.split('!')[0] if self.nickname.lower() == channel.lower(): d = self.factory.getUser(msg) d.addErrback(catchError) d.addCallback(lambda m: "Status of %s: %s" % (msg, m)) d.addCallback(lambda m: self.msg(user, m)) class UserStatusTree(resource.Resource): def __init__(self, service): resource.Resource.__init__(self) self.service = service def render_GET(self, request): d = self.service.getUsers() def formatUsers(users): l = ['<li><a href="%s">%s</a></li>' % (user, user) for user in users] return '<ul>'+''.join(l)+'</ul>' d.addCallback(formatUsers) d.addCallback(request.write) d.addCallback(lambda _: request.finish()) return server.NOT_DONE_YET def getChild(self, path, request): if path=="": return UserStatusTree(self.service) else: return UserStatus(path, self.service) class UserStatus(resource.Resource): def __init__(self, user, service): resource.Resource.__init__(self) self.user = user self.service = service def render_GET(self, request): d = self.service.getUser(self.user) d.addCallback(cgi.escape) d.addCallback(lambda m: '<h1>%s</h1>'%self.user+'<p>%s</p>'%m) d.addCallback(request.write) d.addCallback(lambda _: request.finish()) return server.NOT_DONE_YET class UserStatusXR(xmlrpc.XMLRPC): def __init__(self, service): xmlrpc.XMLRPC.__init__(self) self.service = service def xmlrpc_getUser(self, user): return self.service.getUser(user) class FingerService(service.Service): def __init__(self, filename): self.filename = filename self.users = {} def _read(self): self.users.clear() for line in file(self.filename): user, status = line.split(':', 1) user = user.strip() status = status.strip() self.users[user] = status self.call = reactor.callLater(30, self._read) def getUser(self, user): return defer.succeed(self.users.get(user, "No such user")) def getUsers(self): return defer.succeed(self.users.keys()) def getFingerFactory(self): f = protocol.ServerFactory() f.protocol = FingerProtocol f.getUser = self.getUser return f def getResource(self): r = UserStatusTree(self) x = UserStatusXR(self) r.putChild('RPC2', x) return r def getIRCBot(self, nickname): f = protocol.ReconnectingClientFactory() f.protocol = IRCReplyBot f.nickname = nickname f.getUser = self.getUser return f def startService(self): self._read() service.Service.startService(self) def stopService(self): service.Service.stopService(self) self.call.cancel() application = service.Application('finger', uid=1, gid=1) f = FingerService('/etc/users') serviceCollection = service.IServiceCollection(application) internet.TCPServer(79, f.getFingerFactory() ).setServiceParent(serviceCollection) internet.TCPServer(8000, server.Site(f.getResource()) ).setServiceParent(serviceCollection) internet.TCPClient('irc.freenode.org', 6667, f.getIRCBot('fingerbot') ).setServiceParent(serviceCollection)

Index

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