### Playing around with errors in Python - NameErrors

Let's start with NameErrors, which is one of the more common errors that a newcomer to Python will come across. It is reported when Python can't find a local or global variable in the code. One reason this might pop up is because a variable is being referred to outside of it's namespace. To give you an example

a = 10

def test_f():
a = 20
print a

test_f()
print a


Let's walk through the code. After defining the variable a and the function test_f, you would naively expect the test_f() function call to change the value of a to 20 and print 20. You expect the print statement after the function call to also print 20. Because you expect the function call to have changed the value of a. But, if you try running the code for yourself, you'll notice that the final print statement will print 10. This is where namespaces come into the picture.

def test_f():
b = 20
print b

test_f()
print b


The call to the test_f function will set and print the variable b but the print statement afterwards will throw a NameError because outside of the test_f function, the variable b isn't defined.

Let's look at another example, this time in the context of classes in Python.

class test_c:
b = 20
def test_f(self):
print b

test_c().test_f()


Let me explain the last statement first and then the rest of the example. test_c() creates an instance of the class test_c and test_c().test_f() calls the test_f method on the instance of the class. Naively, you would expect the code print 20, which is the value of the variable b in the class. But instead, you will get a NameError, telling you that the variable b isn't defined. The solution to this problem is to refer to b as self.b inside any of the methods defined on test_c, which tells Python that this variable belongs to the class on which the method is defined.

There are definitely a lot more ways in which you can make Python throw a NameError at you but I wanted to use the NameError to introduce the concept of namespaces in python. That's all for now. And as always, I am thankful for any feedback on the writing style and/or content. Until next time ...

[1]. hilite.me was used to create the inline code blocks.
[2]. You can refer to the Python official documentation on namespaces for more information.
[3]. A Python Shell can be accessed on the official Python page. A more comprehensive editor can be found here.

### Animation using GNUPlot

Animation using GNUPlotI've been trying to create an animation depicting a quasar spectrum moving across the 5 SDSS pass bands with respect to redshift. It is important to visualise what emission lines are moving in and out of bands to be able to understand the color-redshift plots and the changes in it.
I've tried doing this using the animate function in matplotlib, python but i wasn't able to make it work - meaning i worked on it for a couple of days and then i gave up, not having found solutions for my problems on the internet.
And then i came across this site, where the gunn-peterson trough and the lyman alpha forest have been depicted - in a beautiful manner. And this got me interested in using js and d3 to do the animations and make it dynamic - using sliders etc.
In the meanwhile, i thought i'd look up and see if there was a way to create animations in gnuplot and whoopdedoo, what do i find but nirvana!

In the image, you see 5 static curves and one dynam…

### on MOOCs.

For those of you who don't know, MOOC stands for Massively Open Online Course.

The internet is an awesome thing. It's making education free for all. Well, mostly free. But it's surprising at the width and depth of courses being offered online. And it looks like they are also having an impact on students, especially those from universities that are not top ranked. Students in all parts of the world can now get a first class education experience, thanks to courses offered by Stanford, MIT, Caltech, etc.

I'm talking about MOOCs because one of my new year resolutions is to take online courses, atleast 2 per semester (6 months). And I've chosen the following two courses on edX - Analyzing Big Data with Microsoft R Server and Data Science Essentials for now. I looked at courses on Coursera but I couldn't find any which was worthy and free. There are a lot more MOOC providers out there but let's start here. And I feel like the two courses are relevant to where I …

### On programmers.

I just watched this brilliant keynote today. It's a commentary on Programmers and the software development industry/ecosystem as a whole.

I am not going to give you a tl;dr version of the talk because it is a talk that I believe everyone should watch, that everyone should learn from. Instead, I am going to give my own parallel-ish views on programmers and programming.
As pointed out in the talk, there are mythical creatures in the software development industry who are revered as gods. Guido Van Rossum, the creator of Python, was given the title Benevolent Dictator For Life (BDFL). People flock around the creators of popular languages or libraries. They are god-like to most programmers and are treated like gods. By which, I mean to say, we assume they don't have flaws. That they are infallible. That they are perfect.
And alongside this belief in the infallibility of these Gods, we believe that they were born programmers. That programming is something that people are born wit…