为什么csvwriter.writerow()在每个字符后面加一个逗号？

import csv

with open('example.csv', 'w', newline='') as csvfile:
    csvwriter = csv.writer(csvfile)
    csvwriter.writerow(['Column1', 'Column2', 'Column3'])

import csv

data = [
    ['Row1', 'Column1', 'Column2'],
    ['Row2', 'Column1', 'Column2'],
    ['Row3', 'Column1', 'Column2']
]

with open('example.csv', 'w', newline='') as csvfile:
    csvwriter = csv.writer(csvfile)
    csvwriter.writerow(['Column1', 'Column2', 'Column3'])
    for row in data:
        csvwriter.writerow(row)