How to place column name as variable when using Stringindexer in Pyspark

Question

{simpleDF.columns 
 #output :['color', 'lab', 'value1', 'value2']
 indexer = simpleDF.select('lab')

 from pyspark.ml.feature import StringIndexer
 # Let us create an object of the class StringIndexer
 lblindexer=StringIndexer().setInputCol(indexer).setOutputCol("LabelIndexed")
 idxRes=lblindexer.fit(simpleDF).transform(simpleDF)

 idxRes.show(5)}

it is working fine with this line of code but i want it more general

 #lblindexer=StringIndexer().setInputCol('lab').setOutputCol("LabelIndexed")

getting the error: TypeError: Invalid param value given for param "inputCol". Could not convert <class 'pyspark.sql.dataframe.DataFrame'> to string type

Answer 1

Use the column name for the input col, not a dataframe:

lblindexer=StringIndexer().setInputCol('lab').setOutputCol("LabelIndexed")

If you want to use a variable,

indexer = 'lab'
lblindexer=StringIndexer().setInputCol(indexer).setOutputCol("LabelIndexed")