我目前正在尝试制作一个程序，要求用户输入，该程序存储在字典和嵌套字典中。

一切正常，但是令我困惑的一件事是创建一个密钥，该密钥存储在while循环中存储字典的日期时间。

from datetime import datetime

now = datetime.now()
user_list = {}
list_of_users = {}

while True: 

    print("Please enter your desired username below")
    username = input("What is your username? ")

    if username == 'print':
        break

    else:
        first = input("What is your first name? ")

        list_of_users.update({username : user_list})
        user_list['given name'] = first
        user_list['given name'] = username
        user_list['date'] = now.strftime("%Y-%m-%d %H:%M:%S")

print(list_of_users)

这是示例输出。如您所见，字典的日期值具有相同的确切时间。我希望该时间基于while循环中数据的存储时间：

Please enter your desired username below
What is your username? monkey
What is your first name? john
Please enter your desired username below
What is your username? simon
What is your first name? whistler
Please enter your desired username below
What is your username? print
{'monkey': {'given name': 'simon','date': '2019-11-04 13:16:35'},'simon': {'given name': 'simon','date': '2019-11-04 13:16:35'}}

谢谢您的帮助！