Author Dusty Phillips Reviewers

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Which version do you find easier to use? Which is more elegant? What is easier to 
read? These are subjective questions; the answer varies for each of us. Knowing the 
answer, however, is important; if you find you prefer inheritance over composition, 
you have to pay attention that you don't overuse inheritance in your daily coding. If 
you prefer composition, make sure you don't miss opportunities to create an elegant 
inheritance-based solution.
Finally, add some error handlers to the various classes we created in the case study. 
They should ensure single characters are entered, that you don't try to move the 
cursor past the end or beginning of the file, that you don't delete a character that 
doesn't exist, and that you don't save a file without a filename. Try to think of as 
many edge cases as you can, and account for them (thinking about edge cases is 
about 90 percent of a professional programmer's job!) Consider different ways to 
handle them; should you raise an exception when the user tries to move past the
end of the file, or just stay on the last character?
Pay attention, in your daily coding, to the copy and paste commands. Every time
you use them in your editor, consider whether it would be a good idea to improve 
your program's organization so that you only have one version of the code you are 
about to copy.
Summary
In this chapter, we focused on identifying objects, especially objects that are not 
immediately apparent; objects that manage and control. Objects should have both 
data and behavior, but properties can be used to blur the distinction between the 
two. The DRY principle is an important indicator of code quality and inheritance
and composition can be applied to reduce code duplication.
In the next chapter, we'll cover several of the built-in Python data structures and 
objects, focusing on their object-oriented properties and how they can be extended
or adapted.
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