Foundations of Python Network Programming 978-1-4302-3004-5

■ INTRODUCTION
Program Listings
Indentation is always a problem when putting Python programs in a book, because when a program
listing is broken between pages, it can be difficult to determine whether the indentation level happened
to change at the page break. The editors at Apress were very supportive when I offered an idea: we have
inserted light gray chevrons to mark each four-space level of indentation.
We used the » symbol because it is not a valid character in a Python program, and therefore—we
hope—readers will not be confused and try to insert it in their actual listings! Everywhere that you see
the gray double chevron, understand that the actual code listing simply contains a space, and that the
chevrons are there to make the number of spaces easier for you to count. Please let us know whether you
indeed find this innovation more or less confusing than a traditional, unadorned program listing.
To learn a new programming concept, the best thing you can often do is to experiment. To
encourage this, Apress makes the source code for their books' program listings freely available for
download at apress.com. Please take advantage of this and transform the listings on these printed pages
into living programs loaded into your text editor. You are even free to use the code in your own projects!
In the source bundle, I am providing a special treat: even though this book targets Python 2, I have
also provided a Python 3 version of every program listing for which the appropriate libraries are
available. This means that you can take the techniques you learn in these pages and transfer them to the
new version of the language by simply comparing the printed listing with the Python 3 version that you
download.
There are two command-line prompts used in the book, and they are used consistently in their
respective contexts. A single $ is used as the system prompt at which the Python interpreter might be
run, while the famous triple chevron >>> is used for interactive Python interpreter sessions themselves.
If you are familiar with good Python coding practices and with PEP-8, the community's coding
standard, you will note that the program listings here in the printed book deviate in a number of respects
from best practices. You can find PEP-8 here: www.python.org/dev/peps/pep-0008/.
I have varied from standard coding style in the interest of saving trees and to adapt the code to the
printed page. For example, I often shamelessly import several modules in a single statement, instead of
putting each module on its own line. My listings also tend to run commands without performing the
familiar check for whether the script has really been run from the command line:
if __name__ == '__main__':
» ...
This, again, is simply in the interest of space and readability. In the versions of the program listings
provided in the downloadable source code bundle, I have tried to adopt a coding style closer to PEP-8, so
do not be surprised if those listings look a bit different from the ones you see here in the book.
Your Comments
If you need to contact me directly about anything in the book, my e-mail address is
brandon@rhodesmill.org, and I welcome ideas, questions, or constructive criticism. But you should
submit any errata directly to the Apress web site on the page for this particular book, so that they can
maintain the central list of what will have to be revised for the next printing.
Be well; speak respectfully to everyone; write careful tests; and use your newfound powers for
good.Audience
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