Using dictionary or set

can you let me know how i can dictionary set

Please try to explain the goal more clearly. Should the dictionary (or set) be the final result for this part of the code? Or do you think it should help with writing the file? What do you want it to contain after the code runs? What do you think sets and dictionaries are for, exactly - if you don’t know which one you want, then how did you decide that it should be one of them?

And you want… the keys to be all the column names from the input CSV files, and each value to be the name of the file, where the column was found? Or what, exactly?