Instead of summing up the booleans in step 3 to find the total number of missing values, we can take the mean of the Series to get the percentage of values that are missing:

>>> actor_1_fb_likes.isnull().mean()
0.0014

As was mentioned at the beginning of the recipe, it is possible to use parentheses instead of the backslash for multi-line code. Step 4 may be rewritten this way:

>>> (actor_1_fb_likes.fillna(0)
                     .astype(int)
                     .head())

Not all programmers like the use of method chaining, as there are some downsides. One such downside is that debugging becomes difficult. None of the intermediate objects produced during the chain are stored in a variable, so if there is an unexpected result, it will be difficult to trace the exact location in the chain where it occurred.

The example at the start of the recipe may be rewritten so that the result of each method gets preserved as/in a unique variable. This makes tracking bugs much easier, as you can inspect the object at each step:

>>> person1 = person.drive('store')
>>> person2 = person1.buy('food')
>>> person3 = person2.drive('home')
>>> person4 = person3.prepare('food')
>>> person5 = person4.cook('food')
>>> person6 = person5.serve('food')
>>> person7 = person6.eat('food')
>>> person8 = person7.cleanup('dishes')