pyspark给dataframe增加新的一列的实现示例
熟悉pandas的pythoner应该知道给dataframe增加一列很容易，直接以字典形式指定就好了，pyspark中就不同了，摸索了一下，可以使用如下方式增加
frompysparkimportSparkContext frompysparkimportSparkConf frompypsark.sqlimportSparkSession frompyspark.sqlimportfunctions spark=SparkSession.builder.config(conf=SparkConf()).getOrCreate() data=[['Alice',19,'blue','["Alice",19,"blue"]'], ['Jane',20,'green','["Jane",20,"green"]'], ['Mary',21,'blue','["Mary",21,"blue"]'],] frame=spark.createDataFrame(data,schema=["name","age","eye_color","detail"]) frame.cache() frame.show()
+-----+---+---------+--------------------+
|name|age|eye_color| detail|
+-----+---+---------+--------------------+
|Alice|19| blue|["Alice",19,"bl...|
|Jane|20| green|["Jane",20,"gre...|
|Mary|21| blue|["Mary",21,"blue"]|
+-----+---+---------+--------------------+
1、增加常数项
frame2=frame.withColumn("contant",functions.lit(10))
frame2.show()
+-----+---+---------+--------------------+-------+
|name|age|eye_color| detail|contant|
+-----+---+---------+--------------------+-------+
|Alice|19| blue|["Alice",19,"bl...| 10|
|Jane|20| green|["Jane",20,"gre...| 10|
|Mary|21| blue|["Mary",21,"blue"]| 10|
+-----+---+---------+--------------------+-------+
2、简单根据某列进行计算
2.1使用withColumn
frame3_1=frame.withColumn("name_length",functions.length(frame.name))
frame3_1.show()
+-----+---+---------+--------------------+-----------+
|name|age|eye_color| detail|name_length|
+-----+---+---------+--------------------+-----------+
|Alice|19| blue|["Alice",19,"bl...| 5|
|Jane|20| green|["Jane",20,"gre...| 4|
|Mary|21| blue|["Mary",21,"blue"]| 4|
+-----+---+---------+--------------------+-----------+
2.2使用select
frame3_2=frame.select(["name",functions.length(frame.name).alias("name_length")])
frame3_2.show()
+-----+-----------+
|name|name_length|
+-----+-----------+
|Alice| 5|
|Jane| 4|
|Mary| 4|
+-----+-----------+
2.3使用selectExpr
frame3_3=frame.selectExpr(["name","length(name)asname_length"]) frame3_3.show()
+-----+-----------+
|name|name_length|
+-----+-----------+
|Alice| 5|
|Jane| 4|
|Mary| 4|
+-----+-----------+
3、定制化根据某列进行计算
比如我想对某列做指定操作，但是对应的函数没得咋办，造，自己造~
frame4=frame.withColumn("detail_length",functions.UserDefinedFunction(lambdaobj:len(json.loads(obj)))(frame.detail))
#or
deflength_detail(obj):
returnlen(json.loads(obj))
frame4=frame.withColumn("detail_length",functions.UserDefinedFunction(length_detail)(frame.detail))
frame4.show()
+-----+---+---------+--------------------+-------------+
|name|age|eye_color| detail|detail_length|
+-----+---+---------+--------------------+-------------+
|Alice|19| blue|["Alice",19,"bl...| 3|
|Jane|20| green|["Jane",20,"gre...| 3|
|Mary|21| blue|["Mary",21,"blue"]| 3|
+-----+---+---------+--------------------+-------------+
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