.sortByKey(...) transformation

The sortByKey(asc) transformation orders (key, value) RDD by key and returns an RDD in ascending or descending order. Look at the following code snippet:

# Takes the origin code and delays, remove header
# runs a group by origin code via reduceByKey()
# sorting by the key (origin code)
(
    flights
    .zipWithIndex()
    .filter(lambda (row, idx): idx > 0)
    .map(lambda (row, idx): row)
    .map(lambda c: (c[3], int(c[1])))
    .reduceByKey(lambda x, y: x + y)
    .sortByKey()
    .take(50)
)

This will produce this output:

# Output
[(u'ABE', 5113),  
 (u'ABI', 5128),  
 (u'ABQ', 64422),  
 (u'ABY', 1554),  
 (u'ACT', 392),
 ...]