RDD flatMap 操作例子：
flatMap，对原RDD的每个元素(行)执行函数操作，然后把每行都“拍扁”
[training@localhost ~]$ hdfs dfs -put cats.txt
[training@localhost ~]$ hdfs dfa -cat cats.txt
Error: Could not find or load main class dfa
[training@localhost ~]$ hdfs dfs -cat cats.txt
The cat on the mat
The aardvark sat on the sofa
mydata=sc.textFile("cats.txt")
mydata.count()
Out[14]: 2
mydata.take(2)
Out[15]: [u'The cat on the mat', u'The aardvark sat on the sofa']
myflatdata=mydata.flatMap(lambda line: line.split(' '))
myflatdta.count()
Out[19]: 11
myflatdata.take(2)
Out[20]: [u'The', u'cat']
myflatdata.take(11)
Out[21]:
[u'The',
u'cat',
u'on',
u'the',
u'mat',
u'The',
u'aardvark',
u'sat',
u'on',
u'the',
u'sofa']