~justin-fathomdb/nova/justinsb-openstack-api-volumes

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<title>Twisted Documentation: The Evolution of Finger: cleaning up the finger code</title>

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<h1 class="title">The Evolution of Finger: cleaning up the finger code</h1>

<div class="toc"><ol><li><a href="#auto0">Introduction</a></li><li><a href="#auto1">Write Readable Code</a></li></ol></div>

<h2>Introduction<a name="auto0"/></h2>

This is the third part of the Twisted tutorial <a href="index.html" shape="rect">Twisted from Scratch, or The Evolution of Finger</a>.

In this section of the tutorial, we'll clean up our code so that it is

closer to a readable and extendable style.

<h2>Write Readable Code<a name="auto1"/></h2>

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.

<div class="py-listing"><pre> 1

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# Do everything properly

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from twisted.application import internet, service

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from twisted.internet import protocol, reactor, defer

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from twisted.words.protocols import irc

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from twisted.protocols import basic

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from twisted.web import resource, server, static, xmlrpc

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import cgi

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def catchError(err):

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return "Internal error in server"

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class FingerProtocol(basic.LineReceiver):

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def lineReceived(self, user):

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d = self.factory.getUser(user)

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d.addErrback(catchError)

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def writeValue(value):

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self.transport.write(value+'\r\n')

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self.transport.loseConnection()

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d.addCallback(writeValue)

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class IRCReplyBot(irc.IRCClient):

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def connectionMade(self):

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self.nickname = self.factory.nickname

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irc.IRCClient.connectionMade(self)

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def privmsg(self, user, channel, msg):

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user = user.split('!')[0]

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if self.nickname.lower() == channel.lower():

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d.addErrback(catchError)

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d.addCallback(lambda m: "Status of %s: %s" % (msg, m))

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d.addCallback(lambda m: self.msg(user, m))

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class UserStatusTree(resource.Resource):

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def __init__(self, service):

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resource.Resource.__init__(self)

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self.service = service

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def render_GET(self, request):

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d = self.service.getUsers()

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def formatUsers(users):

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l = ['<li><a href="%s">%s</a></li>' % (user, user)

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for user in users]

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return '<ul>'+''.join(l)+'</ul>'

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d.addCallback(formatUsers)

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d.addCallback(request.write)

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d.addCallback(lambda _: request.finish())

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return server.NOT_DONE_YET

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def getChild(self, path, request):

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if path=="":

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return UserStatusTree(self.service)

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else:

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return UserStatus(path, self.service)

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class UserStatus(resource.Resource):

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def __init__(self, user, service):

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resource.Resource.__init__(self)

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self.user = user

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self.service = service

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def render_GET(self, request):

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d = self.service.getUser(self.user)

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d.addCallback(cgi.escape)

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d.addCallback(lambda m:

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'<h1>%s</h1>'%self.user+'%s'%m)

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d.addCallback(request.write)

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d.addCallback(lambda _: request.finish())

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return server.NOT_DONE_YET

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class UserStatusXR(xmlrpc.XMLRPC):

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def __init__(self, service):

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xmlrpc.XMLRPC.__init__(self)

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self.service = service

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def xmlrpc_getUser(self, user):

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return self.service.getUser(user)

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class FingerService(service.Service):

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def __init__(self, filename):

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self.filename = filename

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self.users = {}

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self._read()

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def _read(self):

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self.users.clear()

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for line in file(self.filename):

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user, status = line.split(':', 1)

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user = user.strip()

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status = status.strip()

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self.users[user] = status

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self.call = reactor.callLater(30, self._read)

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def getUser(self, user):

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return defer.succeed(self.users.get(user, "No such user"))

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def getUsers(self):

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def getFingerFactory(self):

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f = protocol.ServerFactory()

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f.protocol = FingerProtocol

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f.getUser = self.getUser

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return f

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def getResource(self):

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r = UserStatusTree(self)

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x = UserStatusXR(self)

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r.putChild('RPC2', x)

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return r

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def getIRCBot(self, nickname):

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f = protocol.ReconnectingClientFactory()

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f.protocol = IRCReplyBot

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f.nickname = nickname

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f.getUser = self.getUser

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return f

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application = service.Application('finger', uid=1, gid=1)

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f = FingerService('/etc/users')

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serviceCollection = service.IServiceCollection(application)

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internet.TCPServer(79, f.getFingerFactory()

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).setServiceParent(serviceCollection)

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internet.TCPServer(8000, server.Site(f.getResource())

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).setServiceParent(serviceCollection)

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internet.TCPClient('irc.freenode.org', 6667, f.getIRCBot('fingerbot')

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).setServiceParent(serviceCollection)

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</pre><div class="caption">Source listing - <a href="listings/finger/finger18.tac">listings/finger/finger18.tac</a></div></div>

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