为什么我写入文件可以保存，但是写时间只能显示不能保存到txt？

while True:
txt = ''
while len(txt)<3:
txt += input("请输入文字:") + '\n'
with open('/storage/emulated/0/1/3.txt', 'a+') as f:
f.write(txt)
from datetime import datetime
import time

    print(datetime.now())

print(datetime.today())

用str()把日期时间类转成字符串型数据就能写入了：

import os
path = 'd:\\mydir'

if not os.path.exists(path):
    os.mkdir(path)

from datetime import datetime

Time = str(datetime.today())

with open(path+'\\test.txt', 'w') as f:
    f.write( Time )