Pythoneer

Now that I dove into functional programming (only using dojo and python, but it’s a start) and feel that my brain has not completely made the switch yet, I come across problems that look like they are best to be solved with functional programming. Isn’t it always that way, when you have started something new and are still excited about it, that the every day problems seem that they want to be solved the new way? Anyway, here it goes.

I got this dictionary. The keys are IDs and the values are kind of a rank. Now I want to sort the IDs by their rank.
I am sure there is a simple one liner for that. But I didn’t come up with it yet.
I only came up with a quite dumb concat, sort and split solution. Not elegant at all.

d = {4: 6, 12: 4, 14: 14, 18: 16, 32: 6,
    33: 24, 40: 27, 41: 6, 44: 25, 106: 2}
d1 = ["%06d" % v+'_'+str(k) for k,v in d.items()]
# d1 is now something like this:
# ['000006_4', '000004_12', '000014_14', '000016_18', ...]
d1.sort() # That allows us to sort, which does it
sorted = [int(i.split("_")[1]) for i in d1 ]

This has several drawbacks, but it was as good as I got :-(.
I hope this has no negative effect on my career.

[Update] Thanks to Daniel’s second post, this is the solution!

sorted(d.items(), key=itemgetter(1))

Awesome, thanks!

After reporting the mentioned bug to the Firefox guys they were not able to confirm it, and they are right!
It seems to be a Firebug bug!
Because if I do the same tests inline in the Firebug Lite console (not the Firefox extension in the browser!) everything works as expected.

>>> [] instanceof Array
true

I keep investigating

See Alex’s blog entry he posted the problem with Firefox3 beta3!
In short

>>> typeof []
"object"
>>> var a = [];
>>> var b = new Array();
>>> a.constructor == b.constructor
false
>>> c = [];
[]
>>> c.constructor == a.constructor
true
>>> d = new Array();
[]
>>> b.constructor == d.constructor;
true
>>> b.constructor == a.constructor;
false

After reading Eugene’s article about functional fun with dojo I wanted to play with dojox.lang.functional, and got stuck right away on one of the first calls.

>>> dojo.require("dojox.lang.functional")
>>> dojo.require("dojox.lang.functional.fold")
>>> df = dojox.lang.functional
>>> df.reduce([1,2,3], "+")
TypeError: a.hasNext is not a function

Oops, that was not what I expected, thanks to Alex’s help Firefox3 beta3 could be identified as the one who causes the problem. And I filed a bug there, so lets hope the next Firefox beta/version does it right.

[Update] The bug seems to be in FireBug, not in Firefox

Yesterday another one of my contributions found it’s way into dojo: dojox.widget.Rating. You can try out the always latest version online in the dojo archive. It’s quite a simple form widget, that allows you to click a star for rating an item. The number of stars and the styling can be adjusted via images and CSS.
If you want an even more flexible way to customize the stars you should look at what Tobi has to offer with his SVG generated stars, they come in many more flavors!

Just because I just came across it while optimizing some old code, I have to mention this.
I have the following list of dictionaries (array or hash-arrays in other words) and I want to sum up the values of one of the items of the dictionary.

In python I do this

    d = [{'value':1, 'title':'one'}, {'value':2}, {'value':3},
         {'value':4, 'title':'four'}, ]
    s = sum([i['value'] for i in d])

In PHP I would have done this (I guess)

    function extract_value($r) {
        return $r['value'];
    }
    $d = array(array('value'=>1, 'title'=>'one'), array('value'=>2),
               array('value'=>3), array('value'=>4, 'title'=>'four'));
    $s = array_sum(array_map("extract_value", $d));

Cracks come forward and shorten it please (in any language!).

I know that already for a long time. And since using dojo I know it even better. And already for a couple of years I am always again coming across functional programming, but never got any deeper into it then using the basic things. But now there is a really juicy piece of fruit I will chew, thanks to Eugene Lazutkin who wrote this wonderful article on Functional JavaScript fun in Dojo. And he also describes what which JS version implements, and more important which browser provides what. Must read!
Thanks …

Ok, watch out for dojo accelerating and passing on the left … Shane O’Sullivan posted, already in december last year about the dojo demo engine. A great step forward and a way to document stuff much better, since you get examples and one tab further you see how it is coded.

It is still in development, but the future looks bright!
So, use all the resources you get …