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

Compute averages

The last step is to transform the pairs of total number of friends and the number of times that key was encountered to an actual average value:

That's what this final line does with mapValues:

averageByAge = totalsByAge.mapValues(lambda x: x[0] / x[1])

Again, we're just receiving the value part of our key/value pair into our lambda function because we're calling mapValues and leaving the keys untouched.

So the age in this example, 33, will remain untouched and not even shown to us in our lambda function:

However, our lambda ...