python - 将表列和值转换为嵌套 JSON

Question

我有一个 CSV 文件，其中的列如下

嵌套 JSON 对象所需的结果如下:

{
"Type" : "A"
"Value" :"1"

}

{
"Type" : "B"
"Value" :"1"

}

我尝试了以下代码:任何帮助将不胜感激。

from pyspark.sql.functions import *

    list1=['A','B','C']
    df2=spark.sql("select * from test   limit  10" )
    df3=df2.select(list1)
    for i in range(0,len(list1)):
      df4=df3.withColumn("Type",lit(list1[i]))

Answer 1

这可以通过 UnPivoting 技巧来完成...

假设您有如下所示的数据集..让我们将其称为患者的测试结果..A、B、C 列表示..测试类型 A 、测试类型 B...以及这些列中的值表示数字形式的测试结果

+-------------+---+---+---+---+---+---+---+
|PatientNumber|  A|  B|  C|  D|  E|  F|  G|
+-------------+---+---+---+---+---+---+---+
|          101|  1|  2|  3|  4|  5|  6|  7|
|          102| 11| 12| 13| 14| 15| 16| 17|
+-------------+---+---+---+---+---+---+---+

我添加了 PatientNumber 列，只是为了使数据看起来更合理。您可以从代码中删除它。

我将此数据集添加到 csv..

val testDF = spark.read.format("csv").option("header", "true").load("""C:\TestData\CSVtoJSon.csv""")

让我们创建 2 个数组，一个用于 id 列，另一个用于所有测试类型..

val idCols = Array("PatientNumber")

val valCols = testDF.columns.diff(idCols)

然后这是 Unpivot 的代码

val valcolNames = valCols.map(x => List(''' + x + ''', x))
val unPivotedDF = testDF.select($"PatientNumber", expr(s"""stack(${valCols.size},${valcolNames.flatMap(x => x).mkString(",")} ) as (Type,Value)"""))

以下是未透视数据的样子 -

+-------------+----+-----+
|PatientNumber|Type|Value|
+-------------+----+-----+
|          101|   A|    1|
|          101|   B|    2|
|          101|   C|    3|
|          101|   D|    4|
|          101|   E|    5|
|          101|   F|    6|
|          101|   G|    7|
|          102|   A|   11|
|          102|   B|   12|
|          102|   C|   13|
|          102|   D|   14|
|          102|   E|   15|
|          102|   F|   16|
|          102|   G|   17|
+-------------+----+-----+

最后将这个 Unpivoted DF 写为 Json -

unPivotedDF.coalesce(1).write.format("json").mode("Overwrite").save("""C:\TestData\output""")

Json 文件的内容看起来与您想要的结果相同 -

{"PatientNumber":"101","Type":"A","Value":"1"}
{"PatientNumber":"101","Type":"B","Value":"2"}
{"PatientNumber":"101","Type":"C","Value":"3"}
{"PatientNumber":"101","Type":"D","Value":"4"}
{"PatientNumber":"101","Type":"E","Value":"5"}
{"PatientNumber":"101","Type":"F","Value":"6"}
{"PatientNumber":"101","Type":"G","Value":"7"}
{"PatientNumber":"102","Type":"A","Value":"11"}
{"PatientNumber":"102","Type":"B","Value":"12"}
{"PatientNumber":"102","Type":"C","Value":"13"}
{"PatientNumber":"102","Type":"D","Value":"14"}
{"PatientNumber":"102","Type":"E","Value":"15"}
{"PatientNumber":"102","Type":"F","Value":"16"}
{"PatientNumber":"102","Type":"G","Value":"17"}