Checking to see if a file exists is a two step process in Python. Simply import the module shown below and invoke the isfile function:

import os.path
os.path.isfile(fname)

The importance of variables in any programming language can’t be emphasised enough. Even if you are a novice, the chances are good that you will have been using variables for quite a while now.

They are the cornerstone of any language and without them we would not be able to accomplish much of anything. However, most of you up until this point have probably only been working with standard variables, variables which can hold single values such as an integer, a single character, or a string of text.

In this tutorial we are going to take a look at a more special type of variable called an array. Arrays can seem quite daunting at first glance but once you get used to working with them you will wonder how you ever managed to program without them.

The reason arrays are special is because they can hold more than one value. Think about this: say you create a variable which contains a line of text like the code below:

Facebook was originally intended as a way for people to stay in touch with friends and family members by sharing pictures and status updates on their timeline. As the website's popularity has grown, so has criticism that it is becoming one giant, online high school.

Online Bullying

There has been a dramatic increase in recent years in the number of online bullying cases due to the introduction of social media. Bullying isn't just limited to younger Facebook users, either. Many adult users have also resorted to bashing others online through nasty status updates and cruel comments.

Prior to social media, bullying in high school involved "kick me" signs and toilet swirling. Facebook and other social media outlets have allowed users to take bullying to a whole other level. Victims can no longer escape bullying by leaving school or work. The torture continues online, at anytime and anyplace.

Status "Likes"

In high school, everyone wants to be part of the popular crowd; people who are outgoing, beautiful, and seem like they have everything.  Posting a status update is similar to wanting to be popular. Once an update is posted, many users wait with bated breath to see how many friends will "like" their status. They believe that the more "likes" they receive, the more popular they are.

If that isn’t enough, there are many Facebook games that involve "liking" someone's status. Games like "Truth Is", where someone likes a status update and in return the poster writes how they really feel about the friend on their Facebook wall. This can get touchy, especially if the two people aren't friends outside of Facebook. It's similar to high school where someone desperately wants another person to like them, but when they find out how that person really feels they are crushed.

Relationships Are Difficult to Keep Private

When someone signs up for Facebook they’re asked to complete their profile, which includes a relationship section. Users can select from different options including "single", "married", "widowed", and "divorced". Whenever someone changes their relationship status, the update shows up on each of their friend's news feeds.

It's easy to see how this feature correlates with high school where everyone talks about who is dating who or which couple broke up. It used to be that after graduation, people were able to keep their relationships more to themselves. Not so anymore in the age of social media. Now everyone has the ability to state their opinion on a friend's relationship status, either by "liking" their status change or by commenting on it.

Facebook has presented many benefits to its users, including the ability to rekindle old high school friendships. What one must understand when they sign up for the service is that they are opening themselves up to the same criticism and drama that takes place in a high school setting.

Proceed with caution!

Python and Ruby, each with roots going back into the 1990s, are two of the most popular interpreted programming languages today. Ruby is most widely known as the language in which the ubiquitous Ruby on Rails web application framework is written, but it also has legions of fans that use it for things that have nothing to do with the web. Python is a big hit in the numerical and scientific computing communities at the present time, rapidly displacing such longtime stalwarts as R when it comes to these applications. It too, however, is also put to a myriad of other uses, and the two languages probably vie for the title when it comes to how flexible their users find them.

A Matter of Personality...

That isn't to say that there aren't some major, immediately noticeable, differences between the two programming tongues. Ruby is famous for its flexibility and eagerness to please; it is seen by many as a cleaned-up continuation of Perl's "Do What I Mean" philosophy, whereby the interpreter does its best to figure out the meaning of evening non-canonical syntactic constructs. In fact, the language's creator, Yukihiro Matsumoto, chose his brainchild's name in homage to that earlier language's gemstone-inspired moniker.

Python, on the other hand, takes a very different tact. In a famous Python Enhancement Proposal called "The Zen of Python," longtime Pythonista Tim Peters declared it to be preferable that there should only be a single obvious way to do anything. Python enthusiasts and programmers, then, generally prize unanimity of style over syntactic flexibility compared to those who choose Ruby, and this shows in the code they create. Even Python's whitespace-sensitive parsing has a feel of lending clarity through syntactical enforcement that is very much at odds with the much fuzzier style of typical Ruby code.

For example, Python's much-admired list comprehension feature serves as the most obvious way to build up certain kinds of lists according to initial conditions:

a = [x**3 for x in range(10,20)]
b = [y for y in a if y % 2 == 0]

first builds up a list of the cubes of all of the numbers between 10 and 19 (yes, 19), assigning the result to 'a'. A second list of those elements in 'a' which are even is then stored in 'b'. One natural way to do this in Ruby is probably:

a = (10..19).map {|x| x ** 3}
b = a.select {|y| y.even?}

but there are a number of obvious alternatives, such as:

a = (10..19).collect do |x|
x ** 3
end

b = a.find_all do |y|
y % 2 == 0
end

It tends to be a little easier to come up with equally viable, but syntactically distinct, solutions in Ruby compared to Python, even for relatively simple tasks like the above. That is not to say that Ruby is a messy language, either; it is merely that it is somewhat freer and more forgiving than Python is, and many consider Python's relative purity in this regard a real advantage when it comes to writing clear, easily understandable code.

And Somewhat One of Performance