tl;dr

Using ensure_ascii=False in json.dump() method will write non-ASCII characters as it is to the file.

with open('data.json', 'w', encoding='utf-8') as f:
    json.dump(data, f, ensure_ascii=False)

Problem

When writing JSON data to a file using json.dump() method, non-ASCII characters such as Korean are not written as it is to the file.
Instead, they are escaped using Unicode escape sequences like this.

{
    "name": "\ud55c\uae00",
    "age": 30
}

Solution

This is because json.dump() method by default encodes data based on the ASCII character set.
To solve this problem, you can use the ensure_ascii=False parameter in the json.dump() method.

import json

data = {
    "name": "한글",
    "age": 30
}

with open('data.json', 'w', encoding='utf-8') as f:
    json.dump(data, f, ensure_ascii=False)

Do not forget to specify the encoding as utf-8 when opening the file to write the JSON data.
If you omit the encoding parameter, the default encoding of the system will be used, which may differ depending on the system and cause encoding errors.