How I can impute a specific row with mean in pandas? : I am trying to impute mean to a specific column in my data frame, the names of the columns are in a list.

for col in ValIndex: #ValIndex has the columns name
    dataSet[col] = dataSet[col].fillna(dataSet[col].mean())

I get this error when I run my code:

can only concatenate str (not "int") to str