What is the point of the finally clause? Why not put any statements you want executed after the try block (regardless of whether or not an exception has been raised) after the entire try ... except clause?
Hint: See what happens if you modify Example E4.5 to put the statements in the finally clause after the try block.
The point of finally in Example E4.5 is that statements in this block get executed before the function returns. If the line
print(' Done with file {}'.format(filename))
were moved to after the try block, it would not be executed if a IOError exception is raised (because the function would have returned to its caller before this print function is encountered.)