df = spark.createDataFrame([(["c", "b", "a","e","f"],'a')], ['arraydata','item'])

df.select(df.arraydata, array_position(f.col("arraydata"),'a')).show()

+---------------+----------------------------+
|      arraydata|array_position(arraydata, a)|
+---------------+----------------------------+
|[c, b, a, e, f]|                           3|
+---------------+----------------------------+

from pyspark.sql.functions import array_position
df.select(df.arraydata, array_position(f.col("arraydata"),f.col("item"))).show()

TypeError: Column is not iterable