Andri Luka 2 years old && Erlang/OTP R13B03 released

This day is very special and remarkable - our son, Andri Luka was born on this day 2 years ago! Happy 2nd Birthday, dear son!

Also, on the other side, Erlang/OTP R13B03 is released. With this release comes the GIT (mirror) repository of Erlang/OTP source code (available here) to enable people to send in contributions. That is awesome! The release also marks the introduction of NIFs (Native Implemented Functions), but that's still in experimental stage.

Icelandic Gaming Industry

Just came back from the first IGI workshop, first workshop for the IGIA10, the Icelandic Gaming Industry Awards competition.. It was an excellent starting point for icelandic indie game developers to meet and network. I came a bit late so I missed few talks, but the rest was really good. The talks were held by representatives from companies that are already established game developers (ie. CCP, Gogogic, Dexoris, etc). It was nice of them to share their expirience in their road to success.

I asked couple of questions, mainly focusing on getting more information on how to get connected to artists and/or designers that want to bring their talent into the gaming industry. Lots of indie developers (such as yours truly) have zero-to-none artistic (design) skills. In my opinion, IGI initiative should also focus on that talent, as well as developers.

As we all know, eye-candy and content is a huge help to make it in this business. I am close to a point where I would definitely need an artist to join me, otherwise it might be very difficult to get players to play the game. Not to mention possible funding :)

Next to come, a bit of introduction to the game itself.

p.s. I encourage you, dear reader, to check the Icelandic Gaming Industry website and join me and others in very interesting endeavour of bringing more games in the future..

Check if an application is running

I'm working on a utility application for Mac OS X, which will display the currently played song in iTunes on the OS X status bar. While working on it, I've made a small utility method to check if a program (identified by BundleID) is running or not.

Here it is:

-(BOOL)isRunning:(NSString *)programBundleId {
    return [[[NSWorkspace sharedWorkspace]
             valueForKeyPath:@"launchedApplications.NSApplicationBundleIdentifier"]
            containsObject:programBundleId] ? YES : NO;
}

The method returns YES if an application is running - in my case, it was useful to check if iTunes is running or not.

TinyURLs reloaded, now with Python3

Few days ago, very smart and great people behind Python project released stable version of Python 3.1; that brings bunch of improvements (including performance ones) and new features. You can check what's new in this release right here, if you wish.

I was quite impressed by the speed improvements over the 3.0.1 version of Python. It's quite fast and comparable to Python 2.6 version (which is pretty damn fast). Running few of my sources with the new version (to test speed and comformance) I noticed that my TinyURL example doesn't work anymore.

The string.letters is gone, and print is (as mentioned before) no longer a statement; it's a function. The updated function now looks like this:

import random
import string

def short_id(num): return "".join(random.sample(string.digits + string.ascii_letters, num))

print(short_id(6))

The only noticable change in the function itself is use of string.ascii_letters. There you have it - now Py3 compliant! :)

Tiny URLs

Want tinyurl.com-style links in your application? Need to generate a random sequence of alphanumerics? Here's a quick function in Python:

import random
import string

def short_id(num): return "".join(random.sample(string.digits + string.letters, num))

print short_id(6)

It will return something like AnLrJl or 9mLXut, or even bK5D4O. Simple and powerful.

Христос се роди! Срећан Божић!

To all the people that celebrate Christmas today, we wish you a Merry Christmas and that you and your family are healthy, happy and wealthy!

Merry Christmas and Happy Holidays!

To all the people that celebrate Christmas, to all my friends and their families, we wish a very Merry Christmas!

Happy Holidays!

Python 3.0 and print function

I have been following the python mailing list for quite some time now. I recommend it for any pythonista who's not afraid of a bit of spam and flame war here and there.

There has been a lot of discussion and arguments about a change in Python 3.0 in which print is a built-in function now instead of a language-specific statement. The arguments started flowing in to the mailing list just minutes after Python 3.0 final was officially released.

Most complaints seem to revolve around the fact that *now* we have to write extra two parenthesis, ie. print("something") instead of print "something". Let us ignore that complaint for now, as it is minor (not to mention pointless) issue, something to get used to and easily solved with IDEs. Besides, we all *know* how to use functions, right? This is a non-issue.

Another (much larger) complaint is about string formatting (PEP-3101 - Advanced String Formatting), which is a very big improvement over the formatting using "%". New built-in function, format(), has been introduced along with (so-called) "Format Specification mini-language" to specify and control formatting. Quite powerful, if you ask me.

Particularly interesting formatting option is formatting of positive and negative numbers (a sign option). Consider implementing this in the old syntax:

print(format(-123456,'#> 20'))
print(format(123456, '#> 20'))
print(format(123456, '#>+20'))

Furthermore, you can implement __format__() method in your classes, which will be called by the format() built-in function for producing a formatted version of the object. However, implementing formatting specification is up to you - you can use the standard formatting syntax or implement your own.

Bottom line is, Python 3.0 brought a lot of changes and improvements; those changes have been discussed and polished over a period of several years prior to releasing the final version. What I don't understand is those people who are complaining about it now, instead of doing it before and contributing to those discussions. It will get some time to get used to the new changes, sure; but don't dismiss them straight away - give it a chance and try it out. You will soon realize that those changes are in fact good ones.

Python 3.0 released

Interestingly, my previous post was about Python 2.6... This one is about 3.0, which finally saw the light of day in final edition two days ago! I just noticed it now (obvious proof I'm spending too much time on meetings here at work :).

Sadly, no official package for OS X as of yet, but I'm sure it will arrive after the weekend. I'm itching to take it for a spin on my code.. There will be some incompatibility issues, but 2.6 version helps a lot to sort that out.

Have a nice weekend, folks!

Python 2.6 final

It's here, the final version of Python 2.6 has been released. This is the last 2.x release of Python before the almighty Py3K. You can read what is new in Python 2.6 and of course, grab your own copy.

I'm fetching the installation now, eager to see if the installation will work with PyObjC on my Mac. Next thing on the list is to install Stackless.

Apple dropping NDA for iPhone Developers

I visited Apple Developer Connection site earlier, looking for some iPhone related resources. There was a message posted there, for all iPhone developers: Apple has decided to drop the non-disclosure agreement for released iPhone software!

In a released message, Apple stated that they have introduced the NDA to protect many of its inventions and innovations that have been put into the iPhone OS. They (finally) recognize that this has put a huge burden (and lots of problems) on the developers so they have decided to drop the whole thing.

However, this agreement is dropped only for developers who have released their software on the Apple Store, the NDA still covers the unreleased software until its release.

This will make a lot of developers much happier. Very good move by Apple!

World is concurrent

Last few years or so, in my free time, I have been coding in Stackless Python. I'm using Python almost exclusively for my projects, so it comes natural to use Stackless for concurrency. Concurrent programming is very interesting and challenging, and Stackless Python makes it (very) bearable and easy.

Stackless Python introduces the concept of microthreads, where tasklets wrap functions allowing them to be launched as microthreads. Scheduling is built in and it can be either cooperative or preemptive. Finally, there are channels which can be used for communication between tasklets. Channels block tasklets, either receiving ones or ones sending, depending on if there is a waiting receiver (or sender, respectively). Another interesting thing is that tasklets can be serialized (pickled) to a disk (or any other storage media) and deserialized later on to be resumed.

Using this functionality provided by Stackless (through a single module) is very easy and intuitive. It keeps the Python code very readable and understandable and it even improves the structure of the program. Common usage patterns are available from the authors of Stackless to help people new to concurrent programming understand principles of how Stackless is used. It allows creating custom tasklet functionality (ie. named tasklets), as well as custom channel functionality (ie. broadcast channels, sending of messages with a timeout, etc).

As I mentioned, scheduling is built in and it is up to a programmer to choose the type: preemptive or cooperative. With cooperative scheduling one has to be careful to write code so that tasklets run cooperatively. During the design and implementation of the tasklets, programmer should pay attention to run the scheduler manually if the operation within the tasklet might make other tasklets suffer for not being able to run. On the other hand, with preemptive scheduling, the scheduler itself is configured to interrupt and reschedule running tasklets. I found the cooperative scheduling more useful in my implementations since it gives more control. You can, however, using preemptive scheduling kindly ask the scheduler not to put your running code back to the scheduling queue. One useful idiom is the Sleeping Tasklets, which blocks the tasklets for a certain period of time. Interestingly, that idiom uses channels to accomplish this.

Documentation of Stackless is available on the website and it covers basic functionality. Also, it offers examples and common patterns (idioms). The module itself is very well documented and available in the python interactive shell by typing help(stackless). The community is active on the mailing list, where help is always available. Every now and then there's a good discussion about the advanced usages of Stackless, and I highly recommend subscribing to the list.

Issues exist, however. Current CPython implementation suffers from the infamous GIL (or, Global Interpreter Lock) which makes it difficult for Python to fully utilize multicore systems (almost every recent computer nowadays). For those who don't know the effects of GIL, it is a mechanism to keep multiple threads from modifying the same object at the same time. Only one thread that acquires a lock on the object may modify that object, and the interpreter controls the acquiring and releasing of the lock, especially around potentially slow operations (such as I/O).

There has been quite a lot of talk about the GIL and whether it should (or not) be removed from Python. Back in '99, few brave souls (Greg Stein and Mark Hammond) tried and removed GIL from the Python code using locks on all mutable structures. According to benchmarks, it actually slowed the execution of code. The results showed that the execution was twice as slow in single threaded environment than with the GIL. If ran on multi-CPU (multi-core) systems, there would be no actual performance gains by removing the GIL.

To truly make the code distributed between CPUs, the solution is to run several python processes and communicate tasklets between them, however that can get (very) complicated, to say the least. Luckily, Python 2.6 (next major release of Python, with final release just around the corner) comes with multiprocessing module. This module supports spawning processes in a similar fashion threading module is used. More so, since the module follows the same API as threading module, it makes refactoring of your projects which use threading a breeze. Process objects can communicate between each other using Queues or Pipes, the latter being bidirectional (both parties represent ends of the pipe, with send() and recv() methods available for sending and receiving).

Using multiprocessing module, you can even distribute your processes remotely, and on top of that, it is possible to create a pool of workers for running tasks. Finally, since the module uses subprocesses instead of threads, the effects of aforementioned GIL can be circumvented.

Stackless by design (because of the scheduler) does not allow tasklets to access (and modify) data structures at the same time. Moreover, in true concurrency fashion, it utilizes channels for passing the data between tasklets. It still has a notion of a shared state between tasklets, but of course, without the dangers. With multiprocessing on Python 2.6, Stackless Python programs will be much more scalable than they are currently, utilizing multi-cpu and multi-core environments more efficiently. That still, however remains to be seen, as porting of Stackless to Python 2.6 is a work in progress.

Enter Erlang! For those of you who don't know what it is, Erlang is a functional programming language (an entirely different approach to programming compared to, ie OOP) designed in Ericsson for the purpose of developing concurrent, distributed, fault-tolerant and (soft) real-time applications.

Being functional, it does not have a concept of a state, it has single variable assignments (just as they taught you in Math classes), dynamic typing, pattern matching of functions (with guards), etc. On top of that, it has extremely lightweight processes with no shared memory. Processes pass messages around to communicate between themselves. Erlang runtime supports very high number of concurrent processes and they are actually abstracted from the operating system. It also supports dynamic distribution of processes, both locally (over multiple CPUs or cores) or remotely (over the network to another Erlang runtime node). Thus, you can build large scale distributed applications that run on machines with many CPUs and on many machines in the network. Since there's no shared state or shared variables, all traditional problems related to concurrency simply disappear as the need for locks is removed.

Erlang does give a lot of headache to a lot of people, because of its syntax. Comparing the syntax with Python's, I can say (being biased and all) that I definitely prefer Python's. On the other hand, I quite like the syntax of Erlang, too. It looked quite bizarre at first, but going through the documentation and examples helped me understand the basics of it. I have just got delivered the Erlang book I purchased, and am very excited to learn more about Erlang. As I have always been more interested in building backend applications, using Erlang seems like a good choice worth learning more about.

As a follow up, next article on this topic will be sprinkled with some code examples, both in Stackless Python and Erlang. I really like learning about new programming languages and frameworks by actually implementing something useful using them, so I will try to do so with Erlang. Some ideas are popping into mind and in next articles I might elaborate more on that, too.

Django on Jython

Few days ago, Leo Soto announced on jython mailing list that Django now runs unmodified on latest Jython code. This is great news for both Jython and Django projects.

Although not my first framework of choice for developing web applications using Python, Django has been adopted by many developers out there, even few ones defecting from Ruby on Rails. Django follows the MVC design pattern, it has url patterns similar to Routes in RoR, etc. One slight problem for developers might be the fact that Django has it's own database API - although I believe another ORM such as SqlAlchemy can be used instead.

I have been following the development of Jython very closely, mainly because I'm planning to introduce it in my company. Our software policy states that the main development language is Java and I'm trying to push the initiative that enables us to use any language as long as it runs in JVM. Nowadays there are several very good (and strong) candidates to replace Java and Jython stands IMHO as one of the strongest. It takes the strengths of Python language and brings them into JVM.

We adopted the Spring Framework in our development to help us minimize the Time to Deliver and maximize the ROI. For developing web applications we're using Spring MVC in both portlet and servlet environments. It improved both the quality of our deliveries and shortened the time to deliver. However, there is still the huge overhead of the code compilation in our day-to-day development. Something like Jython (and Django, possibly) can eliminate that problem partly (or entirely).

Django developers are going for a 1.0 release early next week. With that in mind, the fact that there's an excellent Django Book online and that it runs in Jython are more than enough reasons to get to know Django better and (even) start using it in Enterprise environment. Why not?