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reduce, reuse, recycle

Don’t repeat code; create a function

Take a look at the code that you’ve created so far, which (in an effort to save
you from having your brain explode) has already been amended to process yet
another nested list. Notice anything?
This code is essentially the
same as this code…

for each_item in movies: …which is essentially
if isinstance(each_item, list): the same as this
for nested_item in each_item: code…
if isinstance(nested_item, list):
…which is not
for deeper_item in nested_item: that much
if isinstance(deeper_item, list): different than
for deepest_item in deeper_item: this code.
print(deepest_item)
else:
print(deeper_item)
else:
print(nested_item) There’s not much
four statements, either!
else: difference among these
print(each_item)

This code is beginning to get a little scary…

Your code now contains a lot of repeated code. It’s also a mess to look at, even
though it works with the movie buff’s amended data. All that nesting of for
loops is hard to read, and it’s even harder to ensure that the else suites are
associated with the correct if statement.

There has to be a better way…but what to do?
When code repeats in this way, most programmers look for a way to take
the general pattern of the code and turn it into a reusable function. And
Python programmers think this way, too. Creating a reusable function lets
you invoke the function as needed, as opposed to cutting and pasting existing
code.

So, let’s turn the repeating code into a function.

28 Chapter 1