Exam Associate-Developer-Apache-Spark Topic 1 Question 5 Discussion

Explanation
transactionsDf.sort("predError", ascending=False)
Correct! When using DataFrame.sort() and setting ascending=False, the DataFrame will be sorted by the specified column in descending order, putting all missing values last. An alternative, although not listed as an answer here, would be transactionsDf.sort(desc_nulls_last("predError")).
transactionsDf.sort(asc_nulls_last("predError"))
Incorrect. While this is valid syntax, the DataFrame will be sorted on column predError in ascending order and not in descending order, putting missing values last.
transactionsDf.desc_nulls_last("predError")
Wrong, this is invalid syntax. There is no method DataFrame.desc_nulls_last() in the Spark API. There is a Spark function desc_nulls_last() however (link see below).
transactionsDf.orderBy("predError").desc_nulls_last()
No. While transactionsDf.orderBy("predError") is correct syntax (although it sorts the DataFrame by column predError in ascending order) and returns a DataFrame, there is no method DataFrame.desc_nulls_last() in the Spark API. There is a Spark function desc_nulls_last() however (link see below).
transactionsDf.orderBy("predError").asc_nulls_last()
Incorrect. There is no method DataFrame.asc_nulls_last() in the Spark API (see above).
More info: pyspark.sql.functions.desc_nulls_last - PySpark 3.1.2 documentation and pyspark.sql.DataFrame.sort - PySpark 3.1.2 documentation (https://bit.ly/3g1JtbI , https://bit.ly/2R90NCS) Static notebook | Dynamic notebook: See test 1 (https://flrs.github.io/spark_practice_tests_code/#1/32.html ,
https://bit.ly/sparkpracticeexams_import_instructions)