Comments for krondo http://krondo.com The website of Dave Peticolas Fri, 03 Sep 2010 01:53:44 +0000 hourly 1 http://wordpress.org/?v=3.0.1 Comment on An Introduction to Asynchronous Programming and Twisted by dave http://krondo.com/?p=1682&cpage=1#comment-2942 dave Fri, 03 Sep 2010 01:53:44 +0000 http://krondo.com/blog/?p=1682#comment-2942 Yes, addBoth is very handy. But one thing I've learned teaching (I also teach Python to new programmers): don't try to introduce too many new things at once :) Yes, addBoth is very handy. But one thing I’ve learned teaching (I also teach Python to new programmers): don’t try to introduce too many new things at once :)

]]> Comment on An Introduction to Asynchronous Programming and Twisted by dave http://krondo.com/?p=2441&cpage=1#comment-2941 dave Fri, 03 Sep 2010 01:49:01 +0000 http://krondo.com/blog/?p=2441#comment-2941 Ah, you're trying to pretend that Twisted is really synchronous :) Yeah, that won't work, as you have discovered. You can't mix sync and async code in the same Python process, at least not as easily as you are trying to do. Now you might be able to run Twisted in a separate thread, I believe that has been done before. Then your main thread can still be synchronous. Ah, you’re trying to pretend that Twisted is really synchronous :) Yeah, that won’t work, as you have discovered. You can’t
mix sync and async code in the same Python process, at least not as easily as you are trying to do. Now you might be able
to run Twisted in a separate thread, I believe that has been done before. Then your main thread can still be synchronous.

]]> Comment on Twisted Introduction by dave http://krondo.com/?page_id=1327&cpage=1#comment-2940 dave Fri, 03 Sep 2010 01:39:57 +0000 http://dpeticol.webfactional.com/blog/?page_id=1327#comment-2940 Thank you, I appreciate the kind words! I am specifically aiming this tutorial for people who are new to Twisted and, more importantly, new to asynchronous programming. So your description is apt. Thank you, I appreciate the kind words! I am specifically aiming this tutorial for people who are new to Twisted and, more importantly, new to asynchronous programming. So your description is apt.

]]> Comment on Twisted Introduction by Laurens Van Houtven http://krondo.com/?page_id=1327&cpage=1#comment-2937 Laurens Van Houtven Thu, 02 Sep 2010 22:45:59 +0000 http://dpeticol.webfactional.com/blog/?page_id=1327#comment-2937 I think your tutorials are really awesome, and I love how you're consistently putting so much work into this while remaining responsive and approachable. This was *long* overdue, but the official documentation page now links back to you: http://twistedmatrix.com/trac/wiki/Documentation I couldn't figure out if marketing your tutorials as good-for-newbies or not was doing you a disservice or not; I'm just mainly using them as a pointer for newbies who are willing to learn. If you disagree with the wording, please feel free to e-mail me about it. I think your tutorials are really awesome, and I love how you’re consistently putting so much work into this while remaining responsive and approachable.

This was *long* overdue, but the official documentation page now links back to you:

http://twistedmatrix.com/trac/wiki/Documentation

I couldn’t figure out if marketing your tutorials as good-for-newbies or not was doing you a disservice or not; I’m just mainly using them as a pointer for newbies who are willing to learn. If you disagree with the wording, please feel free to e-mail me about it.

]]> Comment on An Introduction to Asynchronous Programming and Twisted by Laurens Van Houtven http://krondo.com/?p=1682&cpage=1#comment-2936 Laurens Van Houtven Thu, 02 Sep 2010 22:15:37 +0000 http://krondo.com/blog/?p=1682#comment-2936 Yeah, I agree, the second one is definitely best. print, print is just too confusing for people reading 2.x code. More minor nitpicking: there's a convenience method for blocks that conceptually match with "finally" clauses, much like this one: d.addBoth(out) Which, as the name suggests, adds the cb to both the cb and eb chains. Thanks very much for your posts, again lvh Yeah, I agree, the second one is definitely best. print, print is just too confusing for people reading 2.x code.

More minor nitpicking: there’s a convenience method for blocks that conceptually match with “finally” clauses, much like this one:

d.addBoth(out)

Which, as the name suggests, adds the cb to both the cb and eb chains.

Thanks very much for your posts, again
lvh

]]> Comment on An Introduction to Asynchronous Programming and Twisted by Pet http://krondo.com/?p=2441&cpage=1#comment-2932 Pet Thu, 02 Sep 2010 15:54:07 +0000 http://krondo.com/blog/?p=2441#comment-2932 here is formated version of code http://codepad.org/WpvAZH80 here is formated version of code http://codepad.org/WpvAZH80

]]> Comment on An Introduction to Asynchronous Programming and Twisted by Pet http://krondo.com/?p=2441&cpage=1#comment-2931 Pet Thu, 02 Sep 2010 15:50:34 +0000 http://krondo.com/blog/?p=2441#comment-2931 Yes, I know the way with deferredList. I think I'd better explain with example code: there are 2 scripts, the first one is executed and use function from second script. script.py doesn't know that downloader function is asynchronious, that's my idea :) script.py from downloader import downloadPage def main(): print 'calling async function' print 'which will return after its job has been done' downloadPage('http://www.google.com', 'google.txt') print 'page has been downloaded' print 'now i can do other stuff' downloadPage('http://www.yahoo.com', 'yahoo.txt') print 'second page has been downloaded, not printed' main() downloader.py from twisted.web.client import getPage from twisted.internet import defer def _get(url): #from twisted.internet import reactor #I'm using her reactor fo downloading a page with Agent.request() #and saving it to file, but for this example i'm using getPage return getPage(url) def downloadPage(url, filename): def done(_): from twisted.internet import reactor print 'stopping reactor' reactor.stop() @defer.inlineCallbacks def _getPage(url, filename): page = '' try: page = yield _get(url) except Exception, e: print "Exception: ", e if page: print 'got page len', len(page) with open(filename, 'w') as f: f.write(page) defer.returnValue(page) else: print 'no page sorry' defer.returnValue(None) d = _getPage(url, filename) d.addBoth(done) from twisted.internet import reactor reactor.run() Yes, I know the way with deferredList. I think I’d better explain with example code: there are 2 scripts, the first one is executed and use function from second script. script.py doesn’t know that downloader function is asynchronious, that’s my idea :)

script.py
from downloader import downloadPage
def main():

print ‘calling async function’
print ‘which will return after its job has been done’
downloadPage(‘http://www.google.com’, ‘google.txt’)
print ‘page has been downloaded’
print ‘now i can do other stuff’
downloadPage(‘http://www.yahoo.com’, ‘yahoo.txt’)
print ‘second page has been downloaded, not printed’

main()

downloader.py
from twisted.web.client import getPage
from twisted.internet import defer

def _get(url):
#from twisted.internet import reactor
#I’m using her reactor fo downloading a page with Agent.request()
#and saving it to file, but for this example i’m using getPage
return getPage(url)

def downloadPage(url, filename):
def done(_):
from twisted.internet import reactor
print ‘stopping reactor’
reactor.stop()

@defer.inlineCallbacks
def _getPage(url, filename):
page = ”
try:
page = yield _get(url)
except Exception, e:
print “Exception: “, e
if page:
print ‘got page len’, len(page)
with open(filename, ‘w’) as f:
f.write(page)
defer.returnValue(page)
else:
print ‘no page sorry’
defer.returnValue(None)

d = _getPage(url, filename)
d.addBoth(done)

from twisted.internet import reactor
reactor.run()

]]> Comment on An Introduction to Asynchronous Programming and Twisted by dave http://krondo.com/?p=2441&cpage=1#comment-2929 dave Thu, 02 Sep 2010 14:53:59 +0000 http://krondo.com/blog/?p=2441#comment-2929 You want something like this: <code> ds = [] for url in urls: ds.append(downloadPage(url)) dlist = DeferredList(ds) dlist.addCallback(lambda r: reactor.stop()) </code> Make sense? You want something like this:

ds = []
for url in urls:
ds.append(downloadPage(url))
dlist = DeferredList(ds)
dlist.addCallback(lambda r: reactor.stop())

Make sense?

]]> Comment on An Introduction to Asynchronous Programming and Twisted by dave http://krondo.com/?p=2441&cpage=1#comment-2928 dave Thu, 02 Sep 2010 14:52:01 +0000 http://krondo.com/blog/?p=2441#comment-2928 Async will work fine for this, just don't have downloadPage(url) stop the reactor :) Async will work fine for this, just don’t have downloadPage(url) stop the reactor :)

]]> Comment on An Introduction to Asynchronous Programming and Twisted by Pet http://krondo.com/?p=2441&cpage=1#comment-2921 Pet Thu, 02 Sep 2010 07:49:56 +0000 http://krondo.com/blog/?p=2441#comment-2921 Hello Dave, actually I've wanted offer this function downloadPage(url) as utility, so client code could use it everywhere. With DeferredList I could pass a list of urls and download them, but limitation of calling the function only once remains or I should stop reactor in client code after all tasks are done. Looks like using synchronious function would much better in this case Thanks for your help! Hello Dave,

actually I’ve wanted offer this function downloadPage(url) as utility, so client code could use it everywhere. With DeferredList I could pass a list of urls and download them, but limitation of calling the function only once remains or I should stop reactor in client code after all tasks are done. Looks like using synchronious function would much better in this case

Thanks for your help!

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