Question

我有一个字典，每次使用用户创建的用户名和密码运行代码时我都会更新。每当我运行脚本时，更新的键和值都会成功出现在JSON文件中。问题是新的字典值和键替换了JSON文件的内容而不是添加到它们。

my_dict = {}

# there's code here that utilizes the update method for dictionaries to populate #my_dict with a key and value. Due to its length, I'm not posting it. 

with open('data.json', 'r') as f:
    json_string = json.dumps(my_dict)
    json_string


with open('data.json', 'r') as f:
    json.loads(json_string)


with open('data.json', 'w') as f:
    f.write(json_string)

#these successfully write and save the data to the data.json file. When I run #the script again, however, the new data replaces the old data in my_dict. I #want the new my_dict data to be added instead. How do I do this?

Answer 1

在写入文件时使用附加状态，如：

with open('data.json', 'a') as f:
    f.write(json_string)

这将附加字符串，而不是完全替换文件。

Answer 2

如果您需要更新JSON文件只是为了每次都保存相同的字典，我认为您的代码工作正常。

但是如果你需要一个JSON数组，我会在开头插入“[]”。然后在每次迭代时，您可以删除文件的最后一个字符，插入逗号并序列化该字典。这使您的JSON文件成为有效文件。

也许你考虑过这个案子？

import os
import json

my_dict = {}
file_name = "data.json"


def update_dict():
    #update your dictionary here
    my_dict["..."] = ...


if __name__ == "__main__":
    with open(file_name, 'wb+') as file:
        file.write('[]'.encode('utf-8'))

        i = 0

        #do it N times just for testing

        while i < 10:
            update_dict()
            file.seek(-1, os.SEEK_END)
            file.truncate()
            json_str = json.dumps(my_dict)
            file.write(json_str.encode('utf-8'))
            file.write(',]'.encode('utf-8'))
            i += 1

        file.seek(-2, os.SEEK_END)
        file.truncate()
        file.write(']'.encode('utf-8'))
        file.close()

如何将字典的内容存储到json文件中

2 个答案: