<html>

<head></head>

<body>
    <div class="item">
        <div class="item-header">



        </div>

        <div class="item-body">

            <p></p>
            <pre style="padding-left: 30px;">var input = document.getElementById($("#from"));<p></p><p>var autocomplete = new google.maps.places.Autocomplete(input, autoOptions);</p></pre>
            <p></p>
            <p>If you are familiar with both jquery and google places javascript API, you will raise your eyebrows wondering why I am posting such trivial code in this blog. If you really know both apis you are probably grinning from ear to ear because I've run into a problem that you also ran into and managed to solve on your own (cause googling does produce anything helpful). So what gives? what's wrong with the code above? Nothing but it will still produce the following error in the javascript console.</p>
            <p></p>
            <pre style="padding-left: 60px;">Uncaught TypeError: Object [object Object] has no method 'getAttribute'<p></p><p>lL</p><p>uL.(anonymous function).rl</p><p>(anonymous function)</p><p>(anonymous function) %7Bmain,places%7D.js:9</p><p>df.(anonymous function).Lc.c %7Bmain,places%7D.js:24</p><p>L %7Bmain,places%7D.js:9</p><p>ff %7Bmain,places%7D.js:24</p><p>kf %7Bmain,places%7D.js:24</p><p>(anonymous function)</p><p>gf.controls</p><p>(anonymous function) %7Bmain,places%7D.js:24</p><p>b %7Bmain,places%7D.js:10</p><p>df.(anonymous function).Lc %7Bmain,places%7D.js:24</p><p>L %7Bmain,places%7D.js:9</p><p>df.(anonymous function).Lc %7Bmain,places%7D.js:24</p><p>cf.(anonymous function).je %7Bmain,places%7D.js:23</p><p>df.(anonymous function).Lc %7Bmain,places%7D.js:24</p><p>hf %7Bmain,places%7D.js:24</p><p>(anonymous function)</p></pre>
            <p></p>
            <p>&nbsp;</p>
            <p>It took quite a bit of hair pulling before I tried:</p>
            <p></p>
            <pre style="padding-left: 30px;">var input = document.getElementById('from_address');<p></p><p>var autocomplete = new google.maps.places.Autocomplete(input, autoOptions);</p></pre>
            <p></p>
            <p>Wish I was a JS n00b, I would have tried that sooner. Because this works while using a jQuery selector does not!!</p>

        </div>
    </div>


</body>

</html>

Mixing google places and jQuery will lead to frustration

<html>

<head></head>

<body>
    <div class="item">
        <div class="item-header">



        </div>

        <div class="item-body">

            <p></p>
            <p>In my <a href="http://raditha.com/blog/archives/learn-ruby-in-just-under-48-hours.html">learn Ruby in 48 hours project</a>, I left one black box unopened, Now I am attacking it with a hammer and chisel. It's those tiny little ':' symbols scattered all over ruby code that's bugging me. You find them in many different tutorials and books with little or no explaination.</p>
            <p>Sample codes that contain '<code>:</code>' are a plenty in <a href="http://humblelittlerubybook.com/">The Humble Little Ruby Book</a>, but it doesn't explain what these are. Someone had even popped a question about it at <a href="https://stackoverflow.com/questions/6185497/what-do-these-weird-characters-mean">Stackoverflow</a>, and coincidentally he has cited the same example I used in an <a href="http://raditha.com/blog/archives/ruby-on-rails-in-a-day..html">earlier post</a>.</p>
            <p>So what the hell are those things anyway? They are symbols (couldn't they have at least come up with a more imaginative name?). Ok so WTH is a symbol? according to <a href="http://www.randomhacks.net/articles/2007/01/20/13-ways-of-looking-at-a-ruby-symbol">RandomHacks</a> they are memory leaks but that writer gives 12 other explanations as well. <a href="http://www.troubleshooters.com/codecorn/ruby/symbols.htm">Troubleshooters.com</a> says "It's a string. No it's an object. No it's a name."</p>
            <p>Perhaps things would become clearer if we figured out what's the equivalent in PHP, but there isn't an equivalent! How about Python? There isn't one either. Thankfully a good enough explanation can be found on a <a href="http://www.sitepoint.com/learn-ruby-on-rails-4/">SitePoint Ruby on Rails Tutorial</a>: "In Ruby, a <code>Symbol</code> is a simple textual identifier. Like a <code>String</code>, a <code>Symbol</code> is created using literals; the difference is that a <code>Symbol</code> is prefixed with a colon<code> :</code>"</p>
            <p></p>
            <p></p>

        </div>
    </div>


</body>

</html>

Ruby Symbols

<html>

<head></head>

<body>
    <div class="item">
        <div class="item-header">



        </div>

        <div class="item-body">

            <p></p>
            <p>Well, been an year since I had this Toshiba L655D, which was a replacement for my dead macbook. What replace a macbook with a Toshiba? yes. That's pretty obvious! Though I used to own a mac doesn't mean I am a fan boy. At the time the Toshiba was bought, it was more powerful than the Macbook and perhaps even more powerful than some models of MBP that was on offer. Yet the Toshiba was available for almost half the price of a Macbook.</p>
            <p><img alt="" class="aligncenter" height="306" src="http://images.raditha.com/blog/images/2012/toshiba-l655.jpg" width="400"></p>
            <p>Usually the story of my life is that computers, phone and other electronic devices usually die off immidiately after the warranty period has expired. Fortunately in this case the warranty still had a few weeks left to run; or so I thought. Toshiba online warranty checker told me that the warranty had expired six months earlier.</p>
            <p>I immidiately contacted Amazon, who assured me that the warranty is still valid and that I should take it into a shop for repair. That in the case of Sri Lanka is John Keels Office Automation. When I took it there they said the warranty expiration was because I had neglected to register the darned thing. So I did and took it back and they accepted it. That was three days back, still haven't head anything from them. If you ask me, the problem is with the mother board. It's probably stewed</p>
            <p></p>

        </div>
    </div>


</body>

</html>

Toshiba L655D Toast

<html>

<head></head>

<body>
    <div class="item">
        <div class="item-header">



        </div>

        <div class="item-body">

            <p></p>
            <p>Both python and ruby have a <code>yield</code> which is thoroughly confusing to Java programmers and looks like the stuff that <a href="http://raditha.com/blog/archives/learn-ruby-in-24-hours.html">nightmares are made of</a>. But eventually you realize that it isn't so bad after all. But before we deal with our nightmares, we to look at iterators.</p>
            <p>Python for loops look so nifty thanks to iterators. Things like lists and tuples implement the iterator interface. &nbsp;Of course in python you don't need explicit interfaces like what we are used to in Java. However a class that implements <code>def __iter__(self)</code>: and <code>def next(self):</code> can be iterated over. Here is a complete example from the python tutorial.</p>
            <p></p>
            <p></p>

        </div>
    </div>


</body>

</html>

Iterators and Generators and Yields

<html>

<head></head>

<body>
    <div class="item">
        <div class="item-header">



        </div>

        <div class="item-body">

            We've already taken quick glance at python functions elsewhere, and know that they are created with the <code>def</code> keyword, can have default parameters and which part of the code belongs to the function is identified by it's indentation level

            When using default parameters, the PHP approach is that you need to specify the first few parameters and the remainder will be initialized with the defaults. However you cannot 'skip' parameters. For example you can't specify values param1, param2 and then param4 instead of param3. Even if param3 is defined to take a default value the call will fail. This&nbsp;behavior&nbsp;is something that PHP has in common with python except for one thing; &nbsp;you can use name, value pairs to specify only some of the parameters and they do not have to be in order. An example from the <a href="https://docs.python.org/tutorial/controlflow.html">python docs</a> will make this clearer.

            &nbsp;
            <pre style="padding-left: 30px;">def parrot(voltage, state='a stiff', action='voom', type='Norwegian Blue'):
    print "-- This parrot wouldn't", action,
    print "if you put", voltage, "volts through it."
    print "-- Lovely plumage, the", type
    print "-- It's", state, "!"</pre>
            <pre style="padding-left: 30px;"></pre>
            &nbsp;
            <pre style="padding-left: 30px;">parrot(1000)                                          # 1 positional argument
parrot(voltage=1000)                                  # 1 keyword argument
parrot(voltage=1000000, action='VOOOOOM')             # 2 keyword arguments
parrot(action='VOOOOOM', voltage=1000000)             # 2 keyword arguments
parrot('a million', 'bereft of life', 'jump')         # 3 positional arguments
parrot('a thousand', state='pushing up the daisies')  # 1 positional, 1 keyword</pre>
            <pre style="padding-left: 30px;"></pre>
            I said except for one thing , but hang on a second there is one more; &nbsp;default values are initialized only once, so make sure that you don't change the parameters with in the function or there will be hell to pay.

            Many of us have a nasty habit of using parameters that were passed in for temporary storage inside the function. If you have this habit it's perhaps better to use variable number of arguments (in python speak this is&nbsp;arbitrary&nbsp;argument lists) instead of default values.
            <p style="padding-left: 30px;"><code>&nbsp;def my_method(var1, var2, *var3)</code></p>
            Is that Ruby code or python code? Actually I copy pasted that from <a href="http://raditha.com/blog/archives/learning-ruby-in-a-day.html">my recent post on ruby</a>. The syntax is exactly the same the only difference is that Ruby says var3 will be an array and python says it's a list, but it's a classic case of a rose by any other name. As with ruby the * has nothing to do with the * in C

            &nbsp;

            Alternatively, instead of a list or array you can pass in a hash (in ruby) or a dictionary in python as the set of arguments. However if you want to use this approach in python <em>*var3</em> above should be changed to <em>**var3</em>.

            &nbsp;

            <a href="http://www.saltycrane.com/blog/2008/01/how-to-use-args-and-kwargs-in-python/">The Salty Crane</a>&nbsp;explains that it's possible to do the reverse; to pass in a dictionary or a list to a function that does not expect it and isn't even ready to accept a variable list of arguments. Here's how:
            <pre style="padding-left: 30px;">def test_var_args_call(ar, arg2, arg3):
    print "ar:", ar
    print "arg2:", arg2
    print "arg3:", arg3t

kwargs = {"arg3": 3, "arg2": "two"}
test_var_args_call(1, **kwargs)</pre>
            One last thing before you go; lets look at lambda functions. This is how you create an anonymous function in python. But they are not very readable and restricted to just one expression. In short they are almost useless but let's look at an example (from the python docs anyway)

            &nbsp;
            <pre>lambda x: x + n</pre>


            What the hell is that? Python's answer to inline functions.

        </div>
    </div>


</body>

</html>

Python functions

<html>

<head></head>

<body>
    <div class="item">
        <div class="item-header">



        </div>

        <div class="item-body">

            <h2>Modules</h2>
            <p style="padding-left: 30px;">Python says Don't Repeat Yourself. This is made possible by module. A module is just a python script that is 'included' into another one. The syntax for doing that though is with the import keyword. For example if you have a file named <em>crazyModule.py</em> with some code in it you can import it into another script with&nbsp;<span style="color: #008000;"><code><span style="color: #000000;">import crazyModule</span></code>.<span style="color: #000000;"> You can then access functions in it as <code>crazyModule.func1()</code> , <code>crazyModule.func2()</code> and so on and so forth. Or if you are too lazy to keep typing the module name repeatedly you can try:</span></span></p>
            <p style="padding-left: 60px;"><code>from crazyModule import func1, func2</code></p>
            <p style="padding-left: 30px;">That eliminates the need to prefix everything with the module name. All scripts have access to a predefined variable called<span style="color: #000000;"><code> __name__</code></span>&nbsp;<span style="color: #000000;">which as you can guess gives the name of the script. When you call it from the main script it will be set to <code>__main__</code> and inside a module it will have the name of the module. This feature is usefull if you write a bit of code that can be executed on it's own right or can be used as a module.&nbsp;</span></p>
            <p style="padding-left: 30px;">'The built-in function&nbsp;<code><a title="dir" href="https://docs.python.org/library/functions.html#dir"><tt>dir()</tt></a></code>&nbsp;is used to find out which names a module defines. It returns a sorted list of strings:' (<a href="https://docs.python.org/tutorial/modules.html">python tutorial</a>). Here a name means a variable or a function. "<code><a title="dir" href="https://docs.python.org/library/functions.html#dir"><tt>dir()</tt></a>&nbsp;</code>does not list the names of built-in functions and variables. If you want a list of those, they are defined in the standard module&nbsp;<code><a title="__builtin__: The module that provides the built-in namespace." href="https://docs.python.org/library/__builtin__.html#module-__builtin__"><tt>__builtin__</tt></a></code>:"</p>
            <p style="padding-left: 30px;">Too many verbatim quotes from the tutorial already but please do allow me another : "Packages are a way of structuring Python’s module namespace by using 'dotted module names'" &nbsp;this is similar at least in notation and file structure to java packages, with each dot actually representing a subfolder in the <code><span style="color: #000000;">sys.path</span></code>. However a module need not be a class like in Java or Ruby (in Ruby module actually means something else but the import mechanism exists by another name). The other difference is that each folder needs to have a __init__.py . The file can be empty but it has to be there.</p>

            <h2>Classes</h2>
            <p style="padding-left: 30px;">Here is the simplest class that you can make with Python</p>

            <pre style="padding-left: 60px;">class myclass:
   pass</pre>
            <p style="padding-left: 30px;">It's not compulsory to inherit from some super class but if you do need to make derived class the format looks like:</p>

            <pre style="padding-left: 60px;">class myclass(SuperClass):
   pass</pre>
            <p style="padding-left: 30px;">It sure looks like a function call doesn't it? Python classes have a method named<code> __init__</code> that looks like a constructor, smells like one and even sounds like a constructor (<a href="http://www.diveintopython.net/object_oriented_framework/defining_classes.html">Dive into python</a>) but the damned thing is not a constructor. It's actually called after the object has been made. Worse still, &nbsp;current instance is passed as the first parameter! This gets&nbsp;weirder; &nbsp;all class methods need to have <code>self</code> defined as the first parameter, but you don't need to pass it in as a parameter when calling those methods because python will add it automatically! (<a href="http://www.diveintopython.net/object_oriented_framework/defining_classes.html">Dive into python</a>)</p>
            &nbsp;
            <p style="padding-left: 30px;">Defining an __init__ method is option but if you do make one, you must call the ancestors __init__ method excplicitly, and when you do so you need to explicitly add self as a parameter.</p>
            &nbsp;
            <p style="padding-left: 30px;">We have already discussed about using triple quoted strings as the first line in &nbsp;function to serve as it's documentation (we haven't? well you know now). The same thing is possible with classes. If you create such a 'doc string' , it can be retrieved with the <code>__doc__</code> method</p>
            <p style="padding-left: 30px;">How do you create a new instance of a class? certainly not with new! you just pretend the class is a function.</p>
            <p style="padding-left: 60px;"><code>myObjet = MyClass(params)</code></p>
            <p style="padding-left: 30px;">Instance variables (in python these are called data attributes) don't need to be declared. They come into existence when they are first assigned (PHP like behaviour). But then looking at the following statement in the <a href="https://docs.python.org/tutorial/classes.html">python tutorial</a>, one wonders why we even bother with classes in python</p>
            <p style="padding-left: 30px;">Please allow me another quote: "Data attributes override method attributes with the same name; to avoid accidental name conflicts, which may cause hard-to-find bugs in large programs, it is wise to use some kind of convention that minimizes the chance of conflicts."</p>
            <p style="padding-left: 30px;">Attributes may be referenced by methods as well as by ordinary users (“clients”) of an object. In other words, classes are not usable to implement pure abstract data types. In fact, nothing in Python makes it possible to enforce data hiding</p>
            <p style="padding-left: 30px;">Python is language that does not pay lip service to the multiple inheritance is evil mantra. You can make a class inherit from many like so:<code> myClass(super1, super2 ... , supern)</code></p>

            <h2>Pickled objects</h2>
            <p style="padding-left: 30px;">Objects can be serialized and deserliazed with Pickle.</p>

            <pre style="padding-left: 60px;">import pickle
pickle.dump([1,2,3,'aaaa',5],file_handle)</pre>
            <p style="padding-left: 30px;">Easy huh? How do you get out of the pickle you are in? with pickle.load(file_handle). Use sys.stdout and sys.stdin if you just want to see how this works.</p>
            As a footnote, I decided to try out python in 2008 but that project came to note, but at the time I ran into an error named '<a href="http://raditha.com/blog/archives759.html">ImportError: No module named dom.minidom</a>' and my post on it has had a surprising number of views.

        </div>
    </div>


</body>

</html>

Python Packages, Modules and Classes

<html>

<head></head>

<body>
    <div class="item">
        <div class="item-header">



        </div>

        <div class="item-body">

            <p></p>
            <p>On thursday morning <a href="http://raditha.com/blog/archives/python-in-48-hours.html">I set out to learn python</a> and by saturday morning I had read through the official tutorial on the python website as well as gone on numerous side trips on additional references. Blog posts are still paying catch up. You will not find me writing a killer python app in a few days but I can read and understand python code pretty well by now. It's essentially a reproduction of my learn <a href="http://raditha.com/blog/archives/learn-ruby-in-just-under-48-hours.html">Ruby in 48 Hours project</a>.</p>
            <p>Now to set my sites on Django. Should I look at Zope instead? This was supposed to be a PHP killer about a decade ago but seems to have completely fallen by the way side, so probably not. Most python developers today might not even have heard the name. So let's get started with a guide from <a href="http://www.webmonkey.com/2010/02/Install_Django_and_Build_Your_First_App">WebMonkey</a></p>
            <p></p>
            <p></p>

        </div>
    </div>


</body>

</html>