如何在每一行添加行号？

Question

假设这些是我的数据:

‘Maps‘ and ‘Reduces‘ are two phases of solving a query in HDFS.
‘Map’ is responsible to read data from input location.
it will generate a key value pair.
that is, an intermediate output in local machine.
’Reducer’ is responsible to process the intermediate.
output received from the mapper and generate the final output.

我想在每一行添加一个数字,如下面的输出:

1,‘Maps‘ and ‘Reduces‘ are two phases of solving a query in HDFS.
2,‘Map’ is responsible to read data from input location.
3,it will generate a key value pair.
4,that is, an intermediate output in local machine.
5,’Reducer’ is responsible to process the intermediate.
6,output received from the mapper and generate the final output.

将它们保存到文件中.

我试过了:

object DS_E5 {
  def main(args: Array[String]): Unit = {

    var i=0
    val conf = new SparkConf().setAppName("prep").setMaster("local")
    val sc = new SparkContext(conf)
    val sample1 = sc.textFile("data.txt")
    for(sample<-sample1){
      i=i+1
      val ss=sample.map(l=>(i,sample))
      println(ss)
    }
 }
}

但它的输出就像吹:

Vector((1,‘Maps‘ and ‘Reduces‘ are two phases of solving a query in HDFS.))
...

如何编辑我的代码以生成像我最喜欢的输出的输出？

Answer 1

zipWithIndex这就是你需要的.它通过在对的第二个位置添加索引RDD[T]来 映射RDD[(T, Long)].

sample1
   .zipWithIndex()
   .map { case (line, i) => i.toString + ", " + line }

或使用字符串插值(请参阅@ DanielC.Sobral的评论)

sample1
    .zipWithIndex()
    .map { case (line, i) => s"$i, $line" }