pyspark dataframe withColumn command not working

Question

I have a input dataframe: df_input (updated df_input)

|comment|inp_col|inp_val|
|11     |a      |a1     |
|12     |a      |a2     |
         


        

Answer 1

Can you tryout this solution. Your approach may run into whole lot of problems.

import pyspark.sql.functions as F
from pyspark.sql.functions import col
from pyspark.sql.window import Window
#Test data
tst = sqlContext.createDataFrame([(1,'a','3'),(1,'a','4'),(1,'b','5'),(1,'b','7'),(2,'c','&b'),(2,'c','&a'),(2,'d','&b')],schema=['col1','col2','col3'])
# extract the special character out
tst_1 = tst.withColumn("col3_extract",F.substring(F.col('col3'),2,1))
# Selecct which values need to be replaced; withColumnRenamed will also solve spark self join issues
# The substring search can also be done using regex function
tst_filter=tst.where(~F.col('col3').contains('&')).withColumnRenamed('col2','col2_collect')
# For the selected data, perform a collect list
tst_clct = tst_filter.groupby('col2_collect').agg(F.collect_list('col3').alias('col3_collect'))
#%% Join the main table with the collected list
tst_join = tst_1.join(tst_clct,on=tst_1.col3_extract==tst_clct.col2_collect,how='left').drop('col2_collect')
#%% In the column3  replace the values such as a, b
tst_result = tst_join.withColumn("result",F.when(~F.col('col3').contains('&'),F.array(F.col('col3'))).otherwise(F.col('col3_collect')))

Results :

+----+----+----+------------+------------+------+
|col1|col2|col3|col3_extract|col3_collect|result|
+----+----+----+------------+------------+------+
|   2|   c|  &a|           a|      [3, 4]|[3, 4]|
|   2|   c|  &b|           b|      [7, 5]|[7, 5]|
|   2|   d|  &b|           b|      [7, 5]|[7, 5]|
|   1|   a|   3|            |        null|   [3]|
|   1|   a|   4|            |        null|   [4]|
|   1|   b|   5|            |        null|   [5]|
|   1|   b|   7|            |        null|   [7]|
+----+----+----+------------+------------+------+