python - 为什么 json python 程序总是出现错误

Question

我是编程新手，我创建了一个子程序来存储您的姓名，而不是列表中的项目。

import json

list_ = []

filename = 'acco.json'
try:
    with open(filename) as f_obj:
        username = json.load(f_obj)
except FileNotFoundError:
    username = input("What is your name? ")
    while True:
        list_items = input("What is the item you want to add? q to quit")
        if list_items == 'q':
            break
        list_.append(list_items)
    with open(filename, 'w') as f_obj:
        json.dump(username, f_obj)
        print("These is your list of items:")
        print(list_)
        print("We'll remember you when you come back, " + username + "!")
        json.dump(list_items, f_obj)

else:
    print("Welcome back, " + username + "!")
    print("Here are the items of your list:")
    print(_list)

但是，当我运行该程序时，不断出现错误。该错误表明第 8 行有错误，即它所说的代码行

username = json.load(f_obj)

这是确切的错误

Traceback (most recent call last):
  File "/Users/dgranulo/Documents/rememberme.py", line 8, in <module>
    username = json.load(f_obj)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/json/__init__.py", line 296, in load
    parse_constant=parse_constant, object_pairs_hook=object_pairs_hook, **kw)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/json/__init__.py", line 348, in loads
    return _default_decoder.decode(s)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/json/decoder.py", line 340, in decode
    raise JSONDecodeError("Extra data", s, end)
json.decoder.JSONDecodeError: Extra data: line 1 column 8 (char 7)

如果有人可以提供帮助，我们将不胜感激， 谢谢，

Answer 1

您正在将对象一一序列化。一个 str 和一个 list。在 list 或 dict 等集合中执行一次。

这个有效；

>>> print(json.loads('"a"'))
a

但这一个 str 和 list 是一个错误；

>>> json.loads('"a"[1]')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.6/json/__init__.py", line 354, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python3.6/json/decoder.py", line 342, in decode
    raise JSONDecodeError("Extra data", s, end)
json.decoder.JSONDecodeError: Extra data: line 1 column 4 (char 3)

使用dict写入文件；

with open(filename, 'w') as f_obj:
    # json.dump(username, f_obj)
    print("These is your list of items:")
    print(list_)
    print("We'll remember you when you come back, " + username + "!")
    # json.dump(list_items, f_obj)
    # dump a dict
    json.dump({'username': username, 'items': list_}, f_obj)

现在 json.load 将返回一个带有 username 和 items 键的 dict。