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UseCase.html
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<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name="generator" content="Docutils 0.6: http://docutils.sourceforge.net/" />
<title>Things to do with Factory</title>
<style type="text/css">
/*
Author: Peter Parente
Date: 2008/01/22
Version: 1.0
Copyright: This stylesheet has been placed in the public domain - free to edit and use for all uses.
*/
body {
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</head>
<body>
<div class="document" id="things-to-do-with-factory">
<h1 class="title">Things to do with Factory</h1>
<p>Note: I haven't tried many of these.</p>
<div class="section" id="alarm-clock">
<h1>Alarm Clock</h1>
<p>Here's a sketch of an alarm clock. We can inspect & even modify the Factory's argument binding's after creating it - something that cannot be done with a lambda.:</p>
<pre class="literal-block">
def run_at_time(func, time):
"""run callable func some time in the future"""
# register func w/ event loop, etc..
pass
@attributeFactory
def play_mp3(fname):
"""play mp3 file at fname"""
pass
# lambda style
lame_alarm = lambda : play_mp3("Beatles.mp3")
# factory style
better_alarm = play_mp3.factory("Beatles.mp3", time(2, 25, 00)
run_at_time(better_alarm)
# show the alarm
print "At", better_alarm.time, "you'll hear the sweet sounds of" better_alarm.fname[:-4]
# change the song we're going to play
better_alarm.fname = "Hendrix.mp3"
</pre>
</div>
<div class="section" id="creating-objects-in-threads">
<h1>Creating Objects in Threads</h1>
<p>Factories can be used to create independent objects in separate threads:</p>
<pre class="literal-block">
connection_factory = Factory(mysqldb.connect, "example.com", "12345")
def do_stuff(conn_fact):
conn = conn_fact() # makes a *new* connection
cursor = conn.cursor()
cursor.execute("SELECT * FROM PANTS")
...
for i in xrange(3):
t = threading.Thread(do_stuff, args=connection_factory)
t.start()
</pre>
</div>
<div class="section" id="django-style-urlconf">
<h1>Django-style URLConf</h1>
<p>Factories should play nicely with Django-style URL conf:</p>
<pre class="literal-block">
# from django docs:
(r'^feeds/(?P<url>.*)/$', 'django.contrib.syndication.views.feed', {'feed_dict': feeds}),
# using factory:
attributeFactory(django.contrib.syndication.views.feed) # add .factory(..) to existing django func
(r'^feeds/(?P<url>.*)/$', django.contrib.syndication.views.feed.factory(feed_dict=feeds),
</pre>
</div>
<div class="section" id="twisted-callbacks">
<h1>Twisted Callbacks</h1>
<p>Factories could be a better way to write Twisted callbacks:</p>
<pre class="literal-block">
class WebPageMonitor(object):
def __init__(self, sysadmin_email):
self.sysadmin_email = sysadmin_email
@factoryDescriptor
def alert(self, x, url, status):
msg = "Things at", url, "are", status, "because", x
SMTP.mail(msg, to=self.sysadmin_email)
monitor = WebPageMonitor("root@host.com")
def checkPage(url):
"""check on page at URL. Returns deferred"""
def twisted_closure_style(urls_to_check):
for url in urls_to_check:
d = checkPage(url)
def callBack(x):
monitor.alert(x, url=url, status="all cool")
def errBack(x):
monitor.alert(x, url=url, status="on fire")
d.addCallback(callBack))
d.addErrback(errBack)
def factory_style(urls_to_check):
for url in urls_to_check:
d = checkPage(url)
d.addCallback(monitor.alert.factory(status="all cool", url=url))
d.addErrback(monitor.alert.factory(status="on fire", url=url))
def lambda_style(urls_to_check):
for url in urls_to_check:
d = checkPage(url)
d.addCallback(lambda x: monitor.alert(x, status="all cool", url=url))
d.addErrback(lambda x: monitor.alert(x, status="on fire", url=url))
</pre>
</div>
<div class="section" id="objecttemplate">
<h1>ObjectTemplate</h1>
</div>
</div>
</body>
</html>