Explanation
Output of correct code block:
+----------------------------+
|size(split(supplier, , -1))|
+----------------------------+
| 3|
| 1|
| 3|
+----------------------------+
This question shows a typical use case for the split command: Splitting a string into words. An additional difficulty is that you are asked to count the words. Although it is tempting to use the count method here, the size method (as in: size of an array) is actually the correct one to use. Familiarize yourself with the split and the size methods using the linked documentation below.
More info:
Split method: pyspark.sql.functions.split - PySpark 3.1.2 documentation Size method: pyspark.sql.functions.size - PySpark 3.1.2 documentation Static notebook | Dynamic notebook: See test 2