insert an image into a column of csv file.

def image_to_csv(image_path, csv_path, col_num):
  with open(csv_path) as f:
    reader = csv.reader(f)
    # read CSV into list
    data = list(reader)
  # insert image file name into column
  data[0][col_num] = image_path
  # write CSV
  with open(csv_path, 'w') as f:
    writer = csv.writer(f)
    writer.writerows(data)