pyspark : Convert DataFrame to RDD[string]

问题:

I'd like to convert pyspark.sql.dataframe.DataFrame to pyspark.rdd.RDD[String]

I converted a DataFrame df to RDD data:

data = df.rdd
type (data)
## pyspark.rdd.RDD 

the new RDD data contains Row

first = data.first()
type(first)
## pyspark.sql.types.Row

data.first()
Row(_c0=u'aaa', _c1=u'bbb', _c2=u'ccc', _c3=u'ddd')

I'd like to convert Row to list of String , like example below:

u'aaa',u'bbb',u'ccc',u'ddd'

Thanks

回答1:

PySpark Row is just a tuple and can be used as such. All you need here is a simple map (or flatMap if you want to flatten the rows as well) with list:

data.map(list)

or if you expect different types:

data.map(lambda row: [str(c) for c in row])