如何从python中的字典中选择深度嵌套的键：值

Question

我从网站下载了一个 json 数据，我想从嵌套的 json 中选择特定的键：值。我将 json 转换为 python 字典。然后我使用字典理解来选择嵌套的 key:values ，但是嵌套太多了，我相信有比单独扩展每个字典更好的方法。我在我的方法中看到了冗余。你能推荐一个更好的方法吗？

{
    "success": true,
    "payload": {
        "tag": {
            "slug": "python",
            "name": "Python",
            "postCount": 10590,
            "virtuals": {
                "isFollowing": false
            }
        },
        "metadata": {
            "followerCount": 18053,
            "postCount": 10590,
            "coverImage": {
                "id": "1*O3-jbieSsxcQFkrTLp-1zw.gif",
                "originalWidth": 550,
                "originalHeight": 300
            }
        }
    }
}    

我的方法：

从日期时间导入日期时间，时间增量

import json,re

data=r'data.json'
#reads json and converts to dictionary
def js_r(data):
    with open(data, encoding='Latin-1') as f_in:
        return json.load(f_in)

def find_key(obj, key):
    if isinstance(obj, dict):
        yield from iter_dict(obj, key, [])
    elif isinstance(obj, list):
        yield from iter_list(obj, key, [])

def iter_dict(d, key, indices):
    for k, v in d.items():
        if k == key:
            yield indices + [k], v
        if isinstance(v, dict):
            yield from iter_dict(v, key, indices + [k])
        elif isinstance(v, list):
            yield from iter_list(v, key, indices + [k])

def iter_list(seq, key, indices):
    for k, v in enumerate(seq):
        if isinstance(v, dict):
            yield from iter_dict(v, key, indices + [k])
        elif isinstance(v, list):
            yield from iter_list(v, key, indices + [k])
if __name__=="__main__":
    my_dict=js_r(data)
    print ( "This is dictionary for python tag",my_dict)
    keys=my_dict.keys()
    print ("This is the dictionary keys",my_dict.keys())
    my_payload=list(find_key(my_dict,'title'))
    print ("These are my payload",my_payload)
    my_post=iter_dict(my_dict,'User','id')
    print(list(my_post))

Answer 1

我建议您使用python-benedict，这是一个可靠的python dict 子类，具有完整的keypath 支持 和许多实用方法。

它提供多种格式的 IO 支持，包括json。

你可以直接从json文件初始化：

from benedict import benedict

d = benedict.from_json('data.json')

现在你的 dict 有了 keypath 支持：

print(d['payload.metadata.coverImage.id'])

# or use get to avoid a possible KeyError
print(d.get('payload.metadata.coverImage.id'))

安装：pip install python-benedict

这里是库存储库和文档： https://github.com/fabiocaccamo/python-benedict

注意：我是这个项目的作者

Answer 2

以下是您如何使用来自Functions that help to understand json(dict) structure 的find_keys 生成器从该JSON 数据中获取“id”值，以及我随机选择的其他一些键。此代码从字符串中获取 JSON 数据，而不是从文件中读取。

import json

json_data = '''\
{
    "success": true,
    "payload": {
        "tag": {
            "slug": "python",
            "name": "Python",
            "postCount": 10590,
            "virtuals": {
                "isFollowing": false
            }
        },
        "metadata": {
            "followerCount": 18053,
            "postCount": 10590,
            "coverImage": {
                "id": "1*O3-jbieSsxcQFkrTLp-1zw.gif",
                "originalWidth": 550,
                "originalHeight": 300
            }
        }
    }
}
'''

data = r'data.json'

#def js_r(data):
    #with open(data, encoding='Latin-1') as f_in:
        #return json.load(f_in)

# Read the JSON from the inline json_data string instead of from the data file
def js_r(data):
    return json.loads(json_data)

def find_key(obj, key):
    if isinstance(obj, dict):
        yield from iter_dict(obj, key, [])
    elif isinstance(obj, list):
        yield from iter_list(obj, key, [])

def iter_dict(d, key, indices):
    for k, v in d.items():
        if k == key:
            yield indices + [k], v
        if isinstance(v, dict):
            yield from iter_dict(v, key, indices + [k])
        elif isinstance(v, list):
            yield from iter_list(v, key, indices + [k])

def iter_list(seq, key, indices):
    for k, v in enumerate(seq):
        if isinstance(v, dict):
            yield from iter_dict(v, key, indices + [k])
        elif isinstance(v, list):
            yield from iter_list(v, key, indices + [k])

if __name__=="__main__":
    # Read the JSON data
    my_dict = js_r(data)
    print("This is the JSON data:")
    print(json.dumps(my_dict, indent=4), "\n")

    # Find the id key
    keypath, val = next(find_key(my_dict, "id"))
    print("This is the id: {!r}".format(val))
    print("These are the keys that lead to the id:", keypath, "\n")

    # Find the name, followerCount, originalWidth, and originalHeight
    print("Here are some more (key, value) pairs")
    keys = ("name", "followerCount", "originalWidth", "originalHeight")
    for k in keys:
        keypath, val = next(find_key(my_dict, k))
        print("{!r}: {!r}".format(k, val))

输出

This is the JSON data:
{
    "success": true,
    "payload": {
        "tag": {
            "slug": "python",
            "name": "Python",
            "postCount": 10590,
            "virtuals": {
                "isFollowing": false
            }
        },
        "metadata": {
            "followerCount": 18053,
            "postCount": 10590,
            "coverImage": {
                "id": "1*O3-jbieSsxcQFkrTLp-1zw.gif",
                "originalWidth": 550,
                "originalHeight": 300
            }
        }
    }
} 

This is the id: '1*O3-jbieSsxcQFkrTLp-1zw.gif'
These are the keys that lead to the id: ['payload', 'metadata', 'coverImage', 'id'] 

Here are some more (key, value) pairs
'name': 'Python'
'followerCount': 18053
'originalWidth': 550
'originalHeight': 300

---

顺便说一句，JSON 通常使用 UTF 编码，而不是 Latin-1。默认编码是 UTF-8，如果可能，您应该使用它。