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Choosing a Python Web Framework I – bottling it

wizzy — Tue, 03 Aug 2010 12:27:47 +0000

A few years ago, when choosing a Python Web-framework with which to build Showmedo, life was a little simpler. The big CMS frameworks like Zope and its relatively user-friendly little bro Plone were reasonably well established and there were a few up and coming lighter frameworks, which promised to take one closer to the Python. Standouts here were Turbogears and Django.

I tried using Plone, even bought the book, but found it very unwieldy. Like so many frameworks it was perfectly happy until one wanted to do something outside its workflow plan. Then things got icky, really icky. There was also far too much ‘magic’ going on, and far too little connection with the underlying Python. After this experience Turbogears was a breath of fresh air. I could build a web-site in Python and leverage all the efficiency and elegance of the language up close and personal. What could be sweeter? I enjoyed the experience so much I didn’t give Django a fair crack of the whip. Although back then it was in beta and had been postponing a 1.0 release for a very long time.

Well, time moves on, and if there has been anything as intense as a framework war, it’s fair to conclude that Django has taken the spoils. Which seems fair. It’s a fantastically managed project, the documentation seems top notch (very important point), and the community is huge, enthusiastic and growing. For a more flexible experience Pylons is threatening to steal some of Turbogears thunder, offering a more modular, ‘best of breed’ alternative to Django. One of the big advantages here is the possibility of using the superb and acknowledged king of Python ORM database libraries, SQLAlchemy.

Anyway, today I come to praise something at the other end of the spectrum and newish to the field, namely Bottle.py. An entire web-framework packaged in a single Python module, which seemed crazy when first I heard of it. Bottle bills itself as a micro-framework, fast, simple and lightweight. Having had a chance to play around with it, I can testify to this. It makes a superb development server, among other things. After previous battles with Zope/Plone it’s pretty incredible to get a server up and serving pages in a few lines of Python, with one imported module. Here’s the ‘Hello World’ example:

from bottle import route, run

@route('/:name')
def index(name='World'):
    return 'Hello %s!' % name

run(host='localhost', port=8080)

So, if you fancy getting away from the complexity of the bigger frameworks and getting back to basics, Bottle.py is a great option and an amazing achievement.

In the meantime, a little selection of Python web-framework videos from the Showmedo vaults:

Eric Florenzano’s humungous series, Django from the Ground Up.

Jiang Xin’s Pylons series.

Kevin Dangor’s Ultimate DVD Turbogears set. Note: Turbogears 2 has seen some impressive changes to the framework, but much of Kevin’s presentations is still applicable.

We don’t yet have a bottle.py screencast, but there will be one soon. In the meantime, the closest to low-level web-appery we have is John Montgomery’s introduction to Python Web Programming CGI
. Note: this is a club series but the linked introductory video is free and gives an overview.

Relaunch, Refresh, Renew

wizzy — Sun, 23 May 2010 00:35:59 +0000

Not sure what it is, but it starts with re. Inspired somewhat by a good friend (thanks Steve!) I galvanised a few galvons and decided to redo Showmedo. Chief among the aims was:

Make navigation to the video-tutorials much easier/more intuitive.
Make the site less visually er weird/fussy/cluttered
Reorganize and refactor the codebase and remove the huge amounts of cruft behind the scenes to…
Free time in the future.
Make things faster. Page-loads, server-load, the works.
Giving the club a home.

I think pretty substantial inroads have been made with regard to these goals. Not perfect by any means, but there is now a reasonably solid base on which to build. I’ll be documenting the changes a bit in the next week or so, but hope the new site is a much nicer prospect.

Please feel free to direct any feedback here.

cheers,
Kyran

Site Relaunch – customizing that Twitter Widget

wizzy — Thu, 13 May 2010 15:47:00 +0000

With limited time to post any content to the Blog or Twitter micro-blog, being able to reuse/advartise that content seems like a win-win. Twitter helpfully provide a widget for just this purpose but, out of the box, it’s not quite right for my purposes. But with a little javascript, jQuery and CSS magic that can all be put right.

First a little screenshot to show what the vanilla widget looks like, after a bit of customization that you can perform on the Twitter site (you’ll find the widgets hanging off the ‘Goodies’ link at the bottom of your facebook page:

The widget shown is ok but:

I don’t like the header area, with those two Showmedos and a rather redundant Showmedo logo (this is appearing on the Showmedo site).
I’d also like to remove the padding to left and right of the tweets to align the text with the rest of the column content.
The font-used is lucida-grand but I would prefer to use Verdana, the default font for my site.
The ‘twitter’ badge on the bottom left, which is probably most likely to be clicked, takes users to the twitter home page ‘http://twitter.com’ but I would like it to direct to my twitter page ‘http://twitter.com/ShowMeDo’.

With a few a lines of css and jQuery javascript these problems are easily addressed.

First we remove the header by finding its css class, ‘twtr-hd’, and using jQuery to hide it. This is equivalent to setting its css ‘display’ attribute to ‘none’.

$('.twtr-hd').hide();

To change the padding and font-family just add some css to your style-file:

div#contentRight .twtr-widget{
    font-family:Verdana,Arial,Helvetica,"Trebuchet MS",Trebuchet,sans-serif !important;
}

.twtr-widget .twtr-tweet-wrap {
    padding:6px 0 !important;
}

Note the use of the !important flags to override existing settings and escape the css cascade. Now twitter themselves, rather frustratingly, set the widget font-style using an !important tag. This means that in order to override it we need to prioritise our !important using the identity ‘contentRight’ of the right column in which the twitter widget appears.

Lastly, in order to direct users clicking the twitter badge to ShowMeDo’s twitter site we use a little jQuert to change the ‘href’ attribute of the twitter link:

    $('.twtr-doc a').attr('href', 'http://twitter.com/ShowMeDo');

And we have the resulting, pretty satisfactory widget:

Using Python strings and dictionaries to create video embedding templates

wizzy — Sat, 27 Feb 2010 13:31:02 +0000

All Pythonistas will recognize the % operator used to format strings:

print "%s world from %s!"%('hello', 'showmedo')

This is similar to its ‘C’ antecedent but, as you would expect and probably know, Python allows containers other than tuples (in the case containing the ‘hello’ and ’showmedo’ strings) to be used in the string formatting operation.

The use of a dictionary rather than tuple to format the string provides a very handy little templating mechanism, used recently in the addition of video embedding strings to the site.

We start with our text-file template, one long string with no pesky line-breaks:

Note the variables scattered through the string starting with %(width)d. We’ll be using these, together with a Python dictionary, to create our video-specific embedding string. The method that does the legwork is shown below. It is a member of the ‘Video’ class and in this context ’self’ refers to the video instance in question:

def get_embed_string(self, width=425, height=344):
    t_dir = os.path.join(os.path.dirname(__file__),'templates/')
    embed_template = open(t_dir + 'embed_video.txt').read()
    embed_str = embed_template%dict(
                                  width=width,
                                  height=height,
                                  url=movieDirectory() + "%s"%self.get_flv_file_name()
                                  title=self.title,
                                  id='_%d'%self.id
                                  )
    return embed_str

We open the ‘embed_video.txt’ file (using a little Python os magic to establish a relative directory path) and read its contents, storing them in the ‘embed_template’ string. We then use the ‘%’ operator to assign values to the special (of the form %(foo)x) variables in the template, using a Python dictionary.

The resulting ‘embed_str’ string defines a flash

which can be used to embed Showmedo videos in blogs, articles and the like:

Python to the Rescue

wizzy — Thu, 25 Feb 2010 14:59:26 +0000

Showmedo caught some flak from the recent Westhost (our main server-provider) troubles. Catch this pretty interesting thread for the gory details. We were actually pretty lucky as the main site remained standing (not the case for many others) but did manage to lose our cron daemon. As a result some restart scripts which check on the health of, among other things, the Python Turbogears process running the site died. Now this script isn’t needed too often but if the site falls down and we’re literally asleep then it avoids more than a minute or sos downtime. The crontab line in question looks like this:

*/1 * * * * source /.bashrc && /usr/local/bin/python2.5 /home/showmedo/showmedo/cron_start_showmedo.py > /var/log/cron_log

This line tells cron to run cron_start_showmedo.py every minute and the python process will check the health of Showmedo’s main process, our memcache and mysql servers and a few other things and restart them if anything has fallen over. Having lost cron, I needed a quick hack to perform these duties and found some very cool advice here at Slashdot. For various reasons the recommended bash-scripts seemed to be dying on me, and lacking the time or will to try debugging on fairly foreign turf, I hacked a little Python substitute to do much the same:

  1 import time
  2 import subprocess
  3
  4 while 1:
  5     subprocess.Popen(['/usr/local/bin/python2.5', '/home/showmedo/showmedo/cron_start_showmedo.py'])
  6     time.sleep(60)

Not pretty, but at five lines quick and succinct. The line 4 while loop sets things running in perpetuity, line 5 uses Python’s newish (and pretty powerful) subprocess module call the cron_start_showmedo.py module and line 6 takes a 60 second break before continuing the loop.

The script sat duty while I waited for our cron-daemon to return and I slept sounder in my bed as a result.

A Little Downtime :(

wizzy — Mon, 22 Feb 2010 10:34:16 +0000

Having to wear my sysadmin hat a little too often this week. I can honestly state that at least one of the bugs wasn’t my fault. At the moment our cron-jobs (timed unix processes) are failing to engage. So when the site falls down, there’s no handy cron-restart. Should be easy to track down and lots of fun :0

New flash-player being debuted

wizzy — Fri, 08 Jan 2010 22:24:21 +0000

It’s been much more work than anticipated (a definite screencast or three in there somewhere) but we’ve finally moved to the open-source flowplayer Chief benefits are:

much cleaner jquery-like API
far greater control over the video-player area. Which means…
innovative ways of directing users to new content and…
with luck much more interactivity with the video-player

p.s. the commenting on-site is getting a much-needed overhaul. With a bit of cookie-magic we should be able to get some dialogues going and vanquish those nasty anonymous comments (mea culpa).

Python Beginners Completed! – File Input/Output

wizzy — Fri, 16 Oct 2009 08:54:56 +0000

Finally we’ve finished the Python Beginners über-series in our Club. In total the Club has 118 videos over 15 series all focused on teaching new Python skills. Now we’re done with Python beginners we’ll be expanding our scope.

In just under 30 minutes in the File I/O Tutorial I cover reading text files, writing textfiles, using binary files (with Python Imaging Library as the example) and persisting data with the pickle module.

Now that we’re finished with the raw episodes and our Learning Paths are usable I’m tying together all the Python videos (free+Club) into paths-of-learning that teach you about topics including:

Starting to Program with Python
Getting Python Installed
Walking through fully-written programs (long step-by-step series)
Python development environments and tools
Python GUI development
Django
Web-application development

The learning-paths, and learning how to use them effectively, are very much a work in progress. As ever we welcome any and all constructive feedback.

Once we’re done with the Python learning paths we’ll start to tie together all the other topics in ShowMeDo (heck – we have well over 1000 screencast tutorials now!) to make learning much easier.

Python 411 podcast interview – thanks Ron!

Ian — Thu, 28 May 2009 19:41:16 +0000

Ron Stephens, creator of the rather excellent Python411 podcast series was good enough to interview Kyran and myself a couple of weeks back: An interview with the founders of ShowMeDo: May 25, 2009

We cover the history of how we started ShowMeDo with Python screencasts, Kyran’s innovative Learning Paths (which caught MIT’s eye), the special learn-Python-quickly tutorials in our Club, our authors and the 1,000 educational screencasts we’ve built between us to date.

We also discuss how you can share your own knowledge with 100,000 global viewers and end with a light chat about Python 3.0.

Ron has a long list of podcast interviews, check them out if you want to know about topics like Django, Python Visualisation and the Python Learning Foundation. He also lists many Python tutorials across the web, they are great short-cuts to find what you need.

Python Beginners – Club Collection Takes Shape

wizzy — Tue, 05 May 2009 01:25:59 +0000

Have finally got round to giving the Club videos a bit of presentational structure following Ian’s last file I/O series in his huge Beginner Programming With Python.

Ian’s final series in Beginners brings the club total to 118 videos, 15 video-series and over 10 hours of Pythonic video demonstration .

Ian’s beginner-sets were conceived as a whole, from introducing the look and feel of Python to covering, in quite a bit of detail, the general Python programming elements. With Lucas Holland’s introduction to the Python standard libraries we have a nice round number of 50 videos, setting clubbers up nicely for the other club videos and some of the intermediate/advanced Showmedo Python series.

15 New Learning Paths (mostly for Pythonistas)

Ian — Fri, 10 Apr 2009 18:17:47 +0000

We’ve published 15 new Learning Paths to help you build your knowledge of Python, C and Screencasting. The Paths mix free and Club content in a guided journey, pulling out exactly the right episodes and series to help you complete your knowledge for a particular subject.

Popular Paths include:

If you like the idea of these guided tutorials, please give us feedback and help us to spread the word by blogging and tweeting (@showmedo).

Showmedo Relaunching

Ian — Tue, 10 Mar 2009 02:41:03 +0000

Frantic scenes aboard the SS Showmedo as we move to a new server and introduce a much-changed site. According to google analytics about one third of our regular audience are currently lost in cyberspace as various DNS caches around the globe send them off to the old site or some weird fusion of old and new.

Moving server has been as stressful as I imagined, probably the reason for all those ‘moving servers is stressful’ blog entries around the web. We’re currently a little rickety and scared to crank up the engines for fear of shaking the ship apart. But, thanks to some caching magic, we seem to be serving pages and videos.

The new site design is the result of finally having a big chunk of hours to dedicate to Showmedo, rather than cadging them after hours from the day-job. I think things are a deal cleaner and more professional, allowing for my being rather an accidental web-developer. The feedback has been pretty positive, which is always nice.

Our new initiative viz web-education is Learning-paths. I’ll be blogging a little about this as soon as I manage to get the server software installed. For all you linux users out there used to the simple pleasures of ‘apt-get install’ or ‘yum’ or ‘rpm’ or any one of the new-fangled ways of getting software onto your *buntu, opensuse, fedora, etc. box, be very thankful; I have been plunged back a couple of decades or so to library-dependency hell and it is a head-trip indeed.