Frank Kane's Taming Big Data with Apache Spark and Python

Map ()

Just to review, a map function will transform each element of an RDD into one new element. There's always a one-to-one relationship between the RDD you started with and the transformed RDD that you end with. Look at the following figure. Let's say we have a text file that contains the sentence, "The quick red fox jumped over the lazy brown dogs", broken up on different lines as it's shown here. We could then write a mapper that has a lambda function that calls upper on each line that comes in, making everything uppercase. What we get back is exactly the same number of entries, just in uppercase:

We would have started with four lines ...