.flatMap(...) transformation

The flatMap(f) transformation is similar to map, but the new RDD flattens out all of the elements (that is, a sequence of events). Let's look at the following snippet:

# Filter only second column == "WA", 
# select first two columns within the RDD,
# and flatten out all values
(
    airports
    .filter(lambda c: c[1] == "WA")
    .map(lambda c: (c[0], c[1]))
    .flatMap(lambda x: x)
    .take(10)
)

The preceding code will produce the following output:

# Output
[u'Bellingham',  
 u'WA',  
 u'Moses Lake',  
 u'WA',  
 u'Pasco',  
 u'WA',  
 u'Pullman',  
 u'WA',  
 u'Seattle',  
 u'WA']