Python: ValueError: I/O operation on closed file on csv file

Question

When I run the following code:

def read_s_par_csv(file_name):

    with open(file_name,'r') as csvDataFile:
        csvReader = csv.reader(csvDataFile)

        vg = []
        vd = []

        for row in csvReader:
            vg.append(row[0])
            vd.append(row[1])

    return vg,vd


if __name__ == '__main__':
    vg,vd = read_s_par_csv('./s_par_test.csv')
    print(vg)

I get the following error

Traceback (most recent call last):
File "..", line 201, in vg,vd = read_s_par_csv('./s_par_test.csv')
File "..", line 189, in read_s_par_csv for row in csvReader: ValueError: I/O operation on closed file