PySpark-从值列表中添加列

问题描述

我必须根据值列表将列添加到PySpark DataFrame。

a= spark.createDataFrame([("Dog", "Cat"), ("Cat", "Dog"), ("Mouse", "Cat")],["Animal", "Enemy"])

我有一个名为Rating的列表，它是对每只宠物的评级。

rating = [5,4,1]

我需要向数据帧追加一个名为Rating的列，以便

+------+-----+------+
|Animal|Enemy|Rating|
+------+-----+------+
|   Dog|  Cat|     5|
|   Cat|  Dog|     4|
| Mouse|  Cat|     1|
+------+-----+------+

我执行了以下操作，但它只返回评级列中列表中的第一个值

def add_labels():
    return rating.pop(0)

labels_udf = udf(add_labels, IntegerType())

new_df = a.withColumn('Rating', labels_udf()).cache()

输出：

+------+-----+------+
|Animal|Enemy|Rating|
+------+-----+------+
|   Dog|  Cat|     5|
|   Cat|  Dog|     5|
| Mouse|  Cat|     5|
+------+-----+------+

---

解决方案

from pyspark.sql.functions import monotonically_increasing_id, row_number
from pyspark.sql import Window

#sample data
a= sqlContext.createDataFrame([("Dog", "Cat"), ("Cat", "Dog"), ("Mouse", "Cat")],
                               ["Animal", "Enemy"])
a.show()

#convert list to a dataframe
rating = [5,4,1]
b = sqlContext.createDataFrame([(l,) for l in rating], ['Rating'])

#add 'sequential' index and join both dataframe to get the final result
a = a.withColumn("row_idx", row_number().over(Window.orderBy(monotonically_increasing_id())))
b = b.withColumn("row_idx", row_number().over(Window.orderBy(monotonically_increasing_id())))

final_df = a.join(b, a.row_idx == b.row_idx).
             drop("row_idx")
final_df.show()

输入：

+------+-----+
|Animal|Enemy|
+------+-----+
|   Dog|  Cat|
|   Cat|  Dog|
| Mouse|  Cat|
+------+-----+

输出为：

+------+-----+------+
|Animal|Enemy|Rating|
+------+-----+------+
|   Cat|  Dog|     4|
|   Dog|  Cat|     5|
| Mouse|  Cat|     1|
+------+-----+------+