Pivot and Concatenate columns in pyspark dataframe

I have this dataframe below, and I need to get basically one row with all the marks fields concatenated with a delimiter like pipe.
So: PACKAGING MARKS 3|PACKAGING MARKS 2|PACKAG…..

And there can be varying amounts of marks records for each mid.

Thanks

>Solution :

Assuming you want 1 delimited string for each "mid", you can collect all "marks" with collect_list() and use concat_ws() to create the string:

import pyspark.sql.functions as F

df.groupby('mid').agg(F.concat_ws('|', F.collect_list('marks')).alias('marks_str')).show(truncate=False)