How to rename a CSV file by adding MODIFIED in the filename?

[Python_User]

What does this part of the code below? Could you provide some explanation behind the lines of code as comments?

for example, filename = Path('/media/stubens/DataDrive-3XT/projs/T-Z/T/TryStuff/data/csv/IllinoisData.csv')

def read_csv_file(filename):

    parts = list(filename.parts)
    # parts = ['/', 'media', '/', 'stubens', '/', 'DataDrive-3XT','/', 'projs', '/', 'T-Z', '/', 'T', '/', 'TryStuff', '/', 'data', '/', 'csv', '/', 'IllinoisData.csv']

    parts[-1] = f"{filename.stem}Modified{filename.suffix}"
    # parts[-1] = 'IllinoisDataModified.csv'
    # parts = ['/', 'media', '/', 'stubens', '/', 'DataDrive-3XT','/', 'projs', '/', 'T-Z', '/', 'T', '/', 'TryStuff', '/', 'data', '/', 'csv', '/', 'IllinoisDataModified.csv']

    parts[0] = ''
    # removes '/' from index 0 because join will add it back again
    # parts = ['media', '/', 'stubens', '/', 'DataDrive-3XT','/', 'projs', '/', 'T-Z', '/', 'T', '/', 'TryStuff', '/', 'data', '/', 'csv', '/', 'IllinoisDataModified.csv']

    outfilename = Path(f"{'/'.join(parts)}")
    # join fileparts back together
    # outfilename = '/media/stubens/DataDrive-3XT/projs/T-Z/T/TryStuff/data/csv/IllinoisDataModified.csv'
 
    print(f"new output file name: {outfilename}")
    # will print
    # '/media/stubens/DataDrive-3XT/projs/T-Z/T/TryStuff/data/csv/IllinoisDataModified.csv'

    # open two files, filename as input (fp), outfilename as output (fout)
    with filename.open() as fp, outfilename.open('w') as fout:

        # set csv reader to flename (fp)
        crdr = csv.reader(fp, delimiter=',')

        # set csv writer to outfilename (fout), delimiter = ','
        cwrtr = csv.writer(fout, delimiter=',')

        # for each row in crdr (csv input)
        for row in crdr:

            # print the row
            print(row)

            # ...
            # Your code goes here
            # ...

            # write modified row
            cwrtr.writerow(row)

Thanks!!