PySpark replace null in column with value in other column

Question

I want to replace null values in one column with the values in an adjacent column ,for example if i have

A|B
0,1
2,null
3,null
4,2

I want i

Answer 1

At the end found an alternative:

df.withColumn("B",coalesce(df.B,df.A)) 

Answer 2

Another Answer.

If the below df1 your dataframe

rd1 = sc.parallelize([(0,1), (2,None), (3,None), (4,2)])
df1 = rd1.toDF(['A', 'B'])

from pyspark.sql.functions import when
df1.select('A',
           when( df1.B.isNull(), df1.A).otherwise(df1.B).alias('B')
          )\
   .show()

Answer 3

df.rdd.map(lambda row: row if row[1] else Row(a=row[0],b=row[0])).toDF().show()