24 February, 2008

Quick Django Tip: Dynamic Application Object Retrieval

In my recent django adventures I needed to introduce site-wide search functionality and in the process of doing so, encountered a small roadblock towards doing so.  Apparently due to the nature of Django's API for db interaction (as of the last stable release version), there is a limitation as to the use of python variables in API calls.  I found this to be a hinderance, but only for so long.  

The follow code snippet was something I whipped together which by utilising Python's 'eval' built-in, overcame the aforementioned limitation regarding the API's ability to interpolate native Python (e.g. non-django explicit) varaibles.

Things to know to understand the following example:  

 search_input is a list of cleaned and pre-processed user-driven terms, split into separate expressions, (e.g. ["dynamic langauge", "agile", "programming", "paradigm"]). 

 search_schema is a dictionary in which the key is the django model/class through whose objects we are attempting to search, and the value is a list of specific model attributes to attempt said search.  (e.g.   User_Profile : ['firstname' , 'lastname', 'address_1', 'bio_info', 'favourite_books'])

container_xref is a simple alias mapping for the actual django application names to our internal references inside this search code base.  Obviously this whole bit could be written without said setup, but for readability given the scope of the actual application involved, and the fact that I was not searching simply a few static fields in one django application, but several dozen fields through about two dozen separate applications, this container_xref dict was appropriate.   It is through this mapping dict which we place any matched object results (so as to not waste any additional space via unnecessary list initialisations.) for eventual results generation.

Note: the key "total_results" in the container_xref was a simple means of keeping track of overall search matches, rather than relying upon the Django templating engine (view) from doing work responsible from the processing (controller) perspective.  In retrospect, there are better ways this could have been handled, and in future point revisions, this will be addressed.


for search_string in search_input:
  for application in search_schema.keys():
    for attribute in search_schema[application]:
code_to_eval = "%s.objects.filter( %s__icontains='%s' ).order_by('-id')" %       
                     (str(application), str(attribute), str(search_string))
          eval_results = eval(code_to_eval)
          for eval_result in eval_results:
            if eval_result not in container_xref[application]:
              container_xref['total_results'] += 1
        except Exception:
    ### Case specific exception handler types, assignments and resultant actions 
          ### specific to each application in which the above is implemented, go here.


As can be seen from the above, simple inline substitution proceeded by evaluation of said string results in post-compilation dynamic search functionalities within django, addressing simple problems one might run into with the existing API which will most likely be addressed in future versions.  

Your results may vary.


19 February, 2008

Ruby: Somehow I overlooked this Gem of a Language

About 5 years ago I started looking into a language that prior to it's "Rails" fame, was lesser known and even lesser utilised.  I tried it a bit and found it leaving me wanting more.  I've kept tabs on it over the years, reading the tutorials and writing several quasi-AI experimental applications for my SimulaE research, but I ended up being enticed by Python, a language which I stand by, including the wonderful (but until recently unused by me) framework Django (Python's Rail's equivalent, focused on Publishing).   

I've programmed professionally using Python for several contracts/years now and find it quite enjoyable.  In fact, I'm currently coding specifically in Python for Inkedmagonline.com, but that doesn't mean that I don't continue my personal exploration and education for both personal and professional reasons.  I decided to re-experience Ruby by picking up the hallowed PickAxe book and giving it another honest chance.  I'm glad I did.  

I believe that Python, and the values espoused in Tim Peter's "De Zen van Python" (The Zen of Python) (my copy just happens to be in Dutch, otherwise I'd post it for others) have helped me to look at Ruby in a different light.  There are some key differences in the two languages, but I can see now the inherent power in Ruby that I was overlooking before.  In fact, some of those key pieces, syntactically as they were which make Ruby so enticing this time around are the very same 'features' I feel are missing in Python.  It only took me working in an environment with situations where said language features would prove the best solution to the problem(s) on hand for me to realise it.

I am not going to spend time detailing all of the specifics, though I may mention one or two nonetheless.  I'm more so bringing this point up so that others might be reminded that giving something new a single chance might be to your own disadvantage.  After all, I didn't like Python the first time I tried it either.  I think it is partially a matter of how we grow as developers that allow us to know what we're missing, that same spark of realisation that gives us the "a ha" of relief when we find it hiding in a new language, programming methodology, etc.  
What brought me back to looking into Ruby a second time is of all things, Smalltalk.  The whole "everything is an object" concept is nothing new to me, or to programming languages.  However in dynamic strongly typed languages, it is.  More importantly is manner of how even rudimentary objects such as integers, floats and strings are treated in Ruby.  They have methods which can be both called using the standard instance.methodname call format, and have their standard methods overridden.  The second being something far more wonky and kludgy in Python (and a non-option in perl).  

The fact that key methods are instance based such as "len" or "length" for example makes a world of difference for consistency.  It speaks to the overall design that "Matz" (Yukihiro Matsumoto creator of Ruby) had in mind during the planning phase.  In Python, a language in which everything is truly an object as well, this starts to get rather confusing.  While Python does treat every integer and string as an object, it mixes the traditional functional paradigm for calling items such as 'len' so that to find the value of 'a', one would type len(a), as opposed to the more object based a.len ..  This seems counter-intuitive and quite frankly a real surprise when you look at the overall design of Python.

I'm not ripping on Python as I do wholeheartedly enjoy the language, I'm just starting to feel aches and pains over decisions which are ingrained into the language, as well as not being seen as an issue or being addressed in py3k (or Python 3000/Python v3.0) as it were.  I just think that my eyes have been opened to Ruby again and I like what I'm seeing.  I am actively looking to find a future professionally as it were utilising it as nothing beats having fun while accomplishing what one would hope accounts to 'great' things.  We'll see what the future holds.

Next Step:  Migrate my SimulaE virtual world/real model object simulation from Python into Ruby as a test run.  Lather, rinse, repeat and then see what the side-by-side comparison's look like.

Until next time...

05 February, 2008

The Importance of Being Challenged

In this most recent engineering, architecting and development endeavour which I simply refer to as my "job" or "contract", I have come to some conclusions which I feel require sharing.  I'll be very straightforward so as to not waste certain readers' time.  Many of the more seasoned lifetime coders will know (and have experienced many times over) that which I am writing about, which can be summed up as such:  If you are not being constantly challenged, you are atrophying as a developer.

I often write about my own experiences as I know them better than any single other developers experience(s).  This is not because I feel that I'm the end all be all of coders.  Far from it, I do feel that I'm good at what I do, however I prefer to look at my writings as a form of navel gazing, a self-reflective ascertaining how I can better grow in my art and profession.  It is exactly the same manner in which I'm going to proceed regarding today's message.

As I have mentioned, I have most recently jumped into a contract situation at the personal request of a rather successful life-long entrepreneur and given that the opportunity sounded rather interesting, I turned down a salaried position worth almost double because the challenge that was proposed.  Please don't get me wrong, I took a position fixing a half-assed php open-source hot or not style rating system because the employee responsible by no fault of his own necessarily, and due to a lack of a sense of urgency was unable to get a system such as that prescribed, in place by a contractual client deadline.  This was not the reason I took the contract, whilst simultaneously being precisely why I took the contract. 

I'm not a fan of php in its current state (though it has been improved upon since my first dealings with the language), and most definitely not a fan of a vast majority of already written php applications open source or otherwise, but the latter point is more an issue with those specific applications and their designs and integrations.  What I am referring to more so is that I was brough into an environment where it wasn't the same old same old.  Now I wouldn't have stayed were the job going to continually require php specifically and exclusively simply out of my desire at the time to branch out skill-set-wise.   I did know that while I don't consider myself a web developer, I would be required on more than one occasion to work on web applications and having come out of many back-end intensive positions wasn't sure if this is somewhere I'd want to remain.

These weren't to all be simple ones either, any moderately proficient web developer and non-web developer alike could figure a good many of these solutions out.   What really did it for me was that I would be required to not only work under a fairly frequent set of short deadlines due to the nature of the publishing industry as well as the time frame required to keep the site and features current.

The importance of all off these ramblings is this simple point.  Being experienced and disciplined as a Software Engineer/Developer/Architect, etc. ad nauseam helps me to know 'what' I need to do, and gives me insight as to how I might go about solving an issue.  It is however, the actual specifics which put those tidbits of understanding and knowledge into play which go outside a given comfort zone.  It is only then, when we find ourselves in unfamiliar territory, under threat of tight deadlines coupled with our own personal desires to do our best and produce code to which we are proud to associate our name.  

I know that earlier in my career there were times (albeit very few, which I can honestly say) that I too fell into this 'comfort zone'.  I found out though, that this comfort zone is boring and causes one to stagnate.  We code because we love it.  Coding and problem solving is in our blood, and in our hearts.  It is how we look at the world and as such isn't something from which we can remove ourselves.  

If you only know low-level languages, learn a high level language.  If you only work in functional programming paradigms, learn object or aspect oriented ones.  If you only work with interpreted languages, learn compiled langauges, etc.  I'm not saying give up your current lingua franca, I'm simply saying expand your horizons.  The more ways you have of looking at, describing and ultimately understanding a given problem, the more ways you have to solve said problem.  This doesn't solely benefit you, it benefits everyone for whom your code will be written and utilised. 

You knowledge needs to be a living, dynamic pool of information, not a static, never changing one and the way to ensure that is to aggressively fight off the status quo.  Be aggressive, absorb all that you can.  The best way to do this isn't by dipping your toes into the shallow end of the kiddie pool, it is accomplished by putting on your goggles and climbing that high dive, plunging in head first.  

Take a chance for once, you might just learn something.  

Till next time..