Filter expected value from list in df column

I have a data frame with the following column:

raw_col
['a','b','c']
['b']
['a','b']
['c']

I want to return a column with single value based on a conditional statement. I wrote the following function:

def filter_func(elements):
  if "a" in elements:
    return "a"
  else:
    return "Other"

When running the function on the column df.withColumn("col", filter_func("raw_col")) I have the following error col should be Column

What’s wrong here? What should I do?

Answer

You can use array_contains function:

import pyspark.sql.functions as f

df = df.withColumn("col", f.when(f.array_contains("raw_col", f.lit("a")), f.lit("a")).otherwise(f.lit("Other")))

But if you have a complex logic and need necessary use the filter_func, it’s needed to create an UDF:

@f.udf()
def filter_func(elements):
    if "a" in elements:
        return "a"
    else:
        return "Other"

df = df.withColumn("col", filter_func("raw_col"))