python - 为什么在尝试从 JSON 对象中删除值时出现错误 "' unicode' 对象不支持项目删除？

Question

我正在尝试遍历对象列表，从每个对象中删除一个元素。每个对象都是一个新行。然后，我尝试按原样保存新文件，而对象中不包含元素。

{
    "business_id": "fNGIbpazjTRdXgwRY_NIXA",
    "full_address": "1201 Washington Ave\nCarnegie, PA 15106",
    "hours": {
        "Monday": {
            "close": "23:00",
            "open": "11:00"
        },
        "Tuesday": {
            "close": "23:00",
            "open": "11:00"
        },
        "Friday": {
            "close": "23:00",
            "open": "11:00"
        },
        "Wednesday": {
            "close": "23:00",
            "open": "11:00"
        },
        "Thursday": {
            "close": "23:00",
            "open": "11:00"
        },
        "Saturday": {
            "close": "23:00",
            "open": "11:00"
        }
    },
    "open": true,
    "categories": ["Bars", "American (Traditional)", "Nightlife", "Lounges", "Restaurants"],
    "city": "Carnegie",
    "review_count": 7,
    "name": "Rocky's Lounge",
    "neighborhoods": [],
    "longitude": -80.0849416,
    "state": "PA",
    "stars": 4.0,
    "latitude": 40.3964688,
    "attributes": {
        "Alcohol": "full_bar",
        "Noise Level": "average",
        "Music": {
            "dj": false
        },
        "Attire": "casual",
        "Ambience": {
            "romantic": false,
            "intimate": false,
            "touristy": false,
            "hipster": false,
            "divey": false,
            "classy": false,
            "trendy": false,
            "upscale": false,
            "casual": false
        },
        "Good for Kids": true,
        "Wheelchair Accessible": true,
        "Good For Dancing": false,
        "Delivery": false,
        "Dogs Allowed": false,
        "Coat Check": false,
        "Smoking": "no",
        "Accepts Credit Cards": true,
        "Take-out": true,
        "Price Range": 1,
        "Outdoor Seating": false,
        "Takes Reservations": false,
        "Waiter Service": true,
        "Wi-Fi": "free",
        "Caters": false,
        "Good For": {
            "dessert": false,
            "latenight": false,
            "lunch": false,
            "dinner": false,
            "brunch": false,
            "breakfast": false
        },
        "Parking": {
            "garage": false,
            "street": false,
            "validated": false,
            "lot": true,
            "valet": false
        },
        "Has TV": true,
        "Good For Groups": true
    },
    "type": "business"
}

我需要删除 hours 元素中包含的信息，但这些信息并不总是相同的。有的包含所有天数，有的只包含一两天的信息。

这是我试过的代码:

import json

with open('data.json') as data_file:
    data = json.load(data_file)
    for element in data: 
        del element['hours']

但是，我在运行代码时遇到错误:

TypeError: 'unicode' object does not support item deletion

Answer 1

假设您要覆盖同一个文件:

import json

with open('data.json', 'r') as data_file:
    data = json.load(data_file)

for element in data:
    element.pop('hours', None)

with open('data.json', 'w') as data_file:
    data = json.dump(data, data_file)

dict.pop(<key>, not_found=None)如果我了解您的要求，可能就是您要找的东西。因为它会删除 hours如果存在则为 key ，如果不存在则不会失败。

但是我不确定我是否理解为什么 hours 键是否包含几天对你有影响，因为你只是想摆脱整个键/值对，对吧？

现在，如果你真的想使用 del而不是 pop , 以下是如何使您的代码工作:

import json

with open('data.json') as data_file:
    data = json.load(data_file)

for element in data:
    if 'hours' in element:
        del element['hours']

with open('data.json', 'w') as data_file:
    data = json.dump(data, data_file)

如果你想把它写到另一个文件中，只需在第二个文件中更改文件名open声明。

您可能已经注意到，我不得不更改缩进，以便文件在数据清理阶段关闭，并可以在最后被覆盖。

with就是所谓的上下文管理器，无论它提供什么(这里是 data_file 文件描述符)仅在该上下文中可用。这意味着一旦 with 的缩进 block 结束，文件关闭，上下文结束，同时文件描述符变得无效/过时。

如果不这样做，您将无法以写入模式打开文件并获取要写入的新文件描述符。