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)

There has been and continues to be a plethora of observational studies by different researchers in the publishing industry focused on how e-books have affected hard-copy book sales. Evidence from these studies has indicated that there is a significant and monumental shift away from hard-copy books to e-books.[1]These findings precipitate fears that hard-copy books might become more expensive in the near future as they begin to be less available.  This scenario could escalate to the point where only collectors of hard-copy books are willing to pay the high price for ownership.

The founder of Amazon, Jeff Bezos, made a statement in July 2010 that sales of digital books had significantly outstripped U.S. sales of hard-copy. He claimed that Amazon had sold 143 digital books for its e-reader, the Kindle, for every 100 hard-back books over the past three months. The pace of this change was unprecedented;  Amazon said that in the four weeks of June 2010, the rate of sales had reached 180 e-books for every 100 hard-backs sold. Bezos said sales of the Kindle and e-books had reached a "tipping point", with five authors including Steig Larsson, the writer of Girl with a Dragon Tattoo, and Stephenie Meyer, who penned the Twilight series, each selling more than 500,000 digital books.[2] Earlier in July 2010, Hachette said that James Patterson had sold 1.1m e-books to date.

According to a report made by Publishers Weekly, for the first quarter of 2011, e-book sales were up 159.8%; netting sales of $233.1 million. Although adult hard-cover and mass market paperback hard-copies had continued to sell, posting gains in March, all the print segments had declined for the first quarter with the nine mass market houses that report sales. Their findings revealed a 23.4% sales decline, and that children’s paper-back publishers had also declined by 24.1%.[3] E-book sales easily out-distanced mass market paperback sales in the first quarter of 2011 with mass market sales of hard-copy books falling to $123.3 million compared to e-books’ $233.1 million in sales.

According to .net sales report by the March Association of American Publishers (AAP) which collected data and statistics from 1,189 publishers, the adult e-Book sales were $282.3 million in comparison to adult hard-cover book sales which counted $229.6 million during the first quarter of 2012. During the same period in 2011, eBooks revenues were $220.4 million.[4] These reports indicate a disconcerting diminishing demand for hard-copy books.

The earning potential of a software developer largely depends on their knowledge, their chosen area of expertise, experience and flexibility to relocate if necessary.  In the ever changing landscape of Information Technology, many argue that the way to make more money is to specialize in a technology that fewer people are using.  As an example, there are tons of Java programmers out there, but nowhere near enough in lesser known languages such as Perl or Python.  However, there are plenty of opportunities for folks who are willing to burn the midnight oil to gain skills in these niche disciplines.

Because the Information Technology Industry is a rapidly evolving entity, gunning for the "Next Big Thing" is constantly an arm’s length away.  For this reason, developers looking to get requisite knowledge to successfully compete can, for the most part, expect to resign their weekends for the LOVE of code and studying.   And, it’s fair to say that a stick-to-itiveness to teach yourself how to code can be more important than any degree when job prospecting.  Sam Nichols, a mobile developer at SmugMug, puts it this way: “Build a table, build a computer, build a water gun, build a beer bong, build things that will take a week and build things that need to be done in 40 minutes before the party. Making stuff is what this field is all about and getting experience building things, especially with others, especially when it breaks and fails along the way can help with perspective and resiliency.”

Software developers already skilled at writing code are readily able to translate that knowledge to web development. The fact that the information technology sector has shifted largely to web-based infrastructure and software application as system (SaaS) database and operating system capabilities, means that software developers have a wide variety of opportunity in the web development segment of the consulting and job market.

If you are a software developer seeking to increase your earning potential, gaining expertise in  Web development  enhances your ability to attract new opportunities. The more creative a software developer, the far better chance they will have at benefitting from current market demand for new technologies and software innovation. Customization is hot right now, and software developers involved in the creation of updates and unique features to SaaS can add extra value to their portfolio with very little time and effort involved.

 In order for software developers to stay abreast of their field, continuing education and is required to ensure that technical skills are up-to-date. Gaining knowledge in design of computer applications is one of the main objectives in the development and planning of software products.
Once adequate knowledge has been acquired, many software developers can use those insights to develop custom software for a client as a consultant.