Now we all know exec() is cruise-control for awesome. Despising readability, sanity, and performance, I sprinkle my code liberally with this MSG and joyfully await the ensuing migraine. But sometimes I ask myself, is it enough?

Correct Answers Considered Harmful

A wonderfully dynamic language like python lets us take exec() where no string literal has gone before by allowing us to pass in global and local environments that are used for variable lookup. The high-priests of python would have us use this functionality to constrain the side-effects of gratuitious exec()ing, but we can do so much better. A simple subclass of dict() that overrides __getitem__ and only returns the item we’re looking for 50% of the time gives us some ammo:

class AreYouFeelingLuckyDict(dict):
    #this is idealized. see complete source at end of post.
    def __getitem__(self, item):
        if random.choice([True, False]):
            return dict.__getitem__(self, item)
        else:
            raise KeyError(item)

With this dictionary implementation, we can move on to more interesting exec()s:

exec("""a = 1; print a""",
     AreYouFeelingLuckyDict(), #globals
     AreYouFeelingLuckyDict()) #locals

Because python is using instances of AreYouFeelingLuckyDict for global and local variable lookups inside our string of code, half the time the code will work properly. The other half of the time a NameError will be raised. Introducing another variable brings the odds of success to 1 in 4:

exec("""a = 1; b=2; print(a); print(b)""",
     AreYouFeelingLuckyDict(),
     AreYouFeelingLuckyDict())

Of course we can program a bit more defensively and ensure that we’ll get the output we’re looking for. If we encounter a NameError along the way, we simply try, try, and try again:

    exec("""
a=1
b=2
while True:
  try:
    print(a)
    print(b)
    break
  except NameError:
    pass
""", AreYouFeelingLuckyDict(), AreYouFeelingLuckyDict())

Keep in mind that “1″ will most likely be printed out several times as its lookup occurs first (and most persistently) and the exception handling is coarse-grained. The obvious solution is to pipe the output through tail -n 2.

But Wait, There’s More

Becaue of a debilitating gambling problem, bogosort is my favorite sorting algorithm. Bogosort is the equivalent of throwing an array of items onto the floor and seeing if they’ve come up in the proper order. Given a list of N unique items, the odds of getting the answer on the first go round of bogosort are 1 in N!. Running bogosort in production on your company’s machines is like playing roullette (with an enormous wheel and your career). Feel that rush.

But bogosort gets even more awesomer with our exec() trick:

    myglobals = AreYouFeelingLuckyDict(random=random)
    mylocals = AreYouFeelingLuckyDict()
    exec("""
def sorted(is_sorted):
    prev = is_sorted[0]
    for x in is_sorted:
        if prev > x:
            return False
        prev = x
    return True
 
mylist = [4, 1, 9, 5]
runs = 1
while True:
    try:
        is_sorted = []
        while True:
            mutable_mylist = list(mylist)
 
            for i in range(len(mutable_mylist)):
                index = random.randint(0, len(mutable_mylist)-1)
                is_sorted.append(mutable_mylist.pop(index))
 
            if sorted(is_sorted):
                break
            else:
                runs+=1
                is_sorted=[]
        break
    except NameError:
        runs += 1
        pass
""", myglobals, mylocals)

Because I’m a generous man, I’ve modified the AreYouFeelingLuckyDict to always return a result when the item being looked up is “runs”, “NameError”, “True”, “random”, “len”, “list”, “range”, or “sorted.” It’s also worth noting that as soon as we drop into is_sorted() we’re back to a plain-jane, well-behaved locals() with boringly reliable dict-like properties.

With this bogosort modification (err, improvement) and considering a list of length 4, I figure the odds of getting an answer the first time out is 1 in 3,145,824. Now we’re talking! Of course, the code above keeps going until it sorts our list. Running it a few times, I’ve seen the answer produced in as little as 700,000 tries. A paragon of efficiency.

Wink

I hope you’ve enjoyed this. I’ve been playing around with this post for a while and have had a great time. The source to this party can be found in this gist:
https://gist.github.com/945666

Also, please check out Be careful with exec and eval in Python which inspired this post.

In the spirit of ChiPy meetings, I’m declaring 2011 to be the best year yet. I can only assume the best-ness of each passing year will increase monotonically until the year of my death, at which point, all bets are off. Here are some reasons why 2010 was pretty great, too:

• I rode my bike to Saint Louis (without being eaten by possums).
• I went to PyCon.
• My friend Brian and I went to Las Vegas and did not lose large sums of money.
• Erin and Dan took my old apartment and are tending to the compost pile with great fervor.
• Camping with friends occurred more frequently.

And here are some reasons why 2011 will also be great:

• I have no plans to land in the ER, break a bone, receive an IV, or be eaten by possums.
• I will go to PyCon.
• Camping with friends will occur more frequently.
• I will read more books.
• Rob Pike will release Plan10 for download in the iTunes App Store.
• Bjarne Stroustrup will announce that this joke has gone on long enough.
• Cable news channels will not mention the woes of a single teenage starlet, instead focusing on well-researched and thoughtful journalism that is neither sensationalist nor pandering to one side of the aisle or another.
• Robots will stop attempting to submit spam comments to my blog.
• We will meet back here and discuss all this next year.

The first game I’ve ever beaten.  Ever.

http://www.mazapan.se/games/BurnTheRope.php

(you have to burn the rope)

About a year ago I went to see the fine folks at the Loyola Health Center complaining of night time wheezing and shortness of breath when riding bicycles in sub 20 degree temperatures.  After the standard pregnancy test, I summited Mt. Nerdom and was prescribed an albuterol inhaler.  The ‘health care professional’ warned: “this does not necessarily mean you have asthma.”

In the interim I’ve used the inhaler an average of once a month.  However, all usage stopped during my time in Bloomington and quickly picked up after returning to Chicago.  Accompanying my most recent difficulty breathing is the standard allergy-based runny nose.  I now suspect Alice the Cat (see above) is the source of these problems.  In an attempt to alleviate my nasal symptoms I’ve tried the usual claritin but have also resorted to a netipot:

Do not be fooled by the pleasant music.  This is the nasal equivalent of water boarding.  And though the device does seem to work, the “see also: douche” in the wikipedia article on nasal irrigation is quite revealing.

I fear I must soon return to the doctor to find a more comprehensive solution.  Sebastian will not allow me to turn Alice the Cat into Alice the Stirfry, and I am not excited about the prospect of washing her once a week to reduce dander output.  With any luck, some pharmaceutical miracle can restore the cat-man balance while producing interesting side effects (I’m rooting for mood-swings and irritability).

Sebastian’s midnight snack suggestion: “tomato, potato, rice omlet”

I’m enjoying morning courtesy of my friend Keith Folsom (also notice the witty mug my mother gave me).  Keith roasted some beans in his popcorn-maker sized roaster and ground them up for me yesterday. The results are fantastic!  Watch out Metropolis, the Folsom Coffee Company is coming!

September Fourth was the two month anniversary of my vegetarian experiment. I’m eating better, in better shape, and I’ve saved money by eating out less (not to mention the great new dishes I’ve learned to cook). All told, the vegetarian experiment has been a great time and very pro-veggie. I’ve really no desire to eat meat, but I am a bit worried about Thanksgiving and Christmas. I think I’ll stay vegetarian for the indefinite future.

Today’s my birthday, and I think this is the first time it has ever snowed on my birthday (where I was, at least).

I finally download the “Simple Gifts” theme from Copland’s Appalachian Spring ballet today. Based on a shaker tune which was transformed into the “Lord of the Dance” hymn all us Catholic schoolchildren sang, it may be a bit on the hokey side. Nevertheless, it is one of my favorite pieces of music.

We hear the simple but compelling theme over and over: quiet woodwinds, beautiful long-bowing strings, the quick, stacatto brass section, and then that final quiet woodwind (flute?) bit. The orchestra feels as if it’s winding down, yet we know something is coming; we can feel the tension. And then, bam, the trumpet starts back up, coming in gently so as not to startle but with grandiose power not yet heard in the work. It feels like an eternity until that timpani hit one note later, but with that, the whole orchestra enters. They play with such brilliance and majesty. It’s as if we’ve been waiting for this for the entire piece, but they do not rush and instead each note comes through with feeling and restraint.

I would to love see Appalachian Spring performed someday. Until then, we can all enjoy this 1996 Oldsmobile Aurora commercial; the cheese here is unsurpassed, and yet the whole thing (even without the towers) feels nostalgically pre-9/11.

In kindergarten we’d sometimes have to stay inside for recess because of the weather. When this happened the teacher would occasionally play the ‘popcorn song’ and make us dance. It was a great song. I heard it today on NPR, and a quick googling brought up: http://www.popcorn-song.com/

Apparently you could just build a complete library of popcorn songs. Brilliant.