.sample(...) transformation

The sample(withReplacement, fraction, seed) transformation samples a fraction of the data, with or without replacement (the withReplacement parameter), based on a random seed. 

Look at the following code snippet:

# Provide a sample based on 0.001% the
# flights RDD data specific to the fourth
# column (origin city of flight)
# without replacement (False) using random
# seed of 123 
(
    flights
    .map(lambda c: c[3])
    .sample(False, 0.001, 123)
    .take(5)
)

We can expect the following result:

# Output
[u'ABQ', u'AEX', u'AGS', u'ANC', u'ATL']