csv writer没有关闭文件

import csv

with open('example.csv', 'w', newline='') as csvfile:
    writer = csv.writer(csvfile)
    writer.writerow(['Name', 'Age'])
    writer.writerow(['Alice', 30])
    writer.writerow(['Bob', 25])

import csv

csvfile = open('example.csv', 'w', newline='')
writer = csv.writer(csvfile)
writer.writerow(['Name', 'Age'])
writer.writerow(['Alice', 30])
writer.writerow(['Bob', 25])
csvfile.close()