当我尝试提取特定值时，json文件出现关键错误

Question

我想将所有这些元素作为列按以下顺序制作一个数据框：

来自“播放列表”： 'name'、'collaborative'、'pid'、'modified_at'、'num_tracks'、'num_albums'、'num_followers'、 'num_edits'、'duration_ms'、'num_artists'

来自“轨道”： '位置'， 'artist_name'、'track_uri'、'artist_uri'、'track_name'、'album_uri'、'duration_ms'、'album_name'

来自“信息”： 'generated_on'、'slice'、'版本'

json文件的一部分如下：

{
    "info": {
        "generated_on": "2017-12-03 08:41:42.057563", 
        "slice": "0-999", 
        "version": "v1"
    }, 
    "playlists": [
        {
            "name": "Throwbacks", 
            "collaborative": "false", 
            "pid": 0, 
            "modified_at": 1493424000, 
            "num_tracks": 52, 
            "num_albums": 47, 
            "num_followers": 1, 
            "tracks": [
                {
                    "pos": 0, 
                    "artist_name": "Missy Elliott", 
                    "track_uri": "spotify:track:0UaMYEvWZi0ZqiDOoHU3YI", 
                    "artist_uri": "spotify:artist:2wIVse2owClT7go1WT98tk", 
                    "track_name": "Lose Control (feat. Ciara & Fat Man Scoop)", 
                    "album_uri": "spotify:album:6vV5UrXcfyQD1wu4Qo2I9K", 
                    "duration_ms": 226863, 
                    "album_name": "The Cookbook"
                }, 
                {
                    "pos": 1, 
                    "artist_name": "Britney Spears", 
                    "track_uri": "spotify:track:6I9VzXrHxO9rA9A5euc8Ak", 
                    "artist_uri": "spotify:artist:26dSoYclwsYLMAKD3tpOr4", 
                    "track_name": "Toxic", 
                    "album_uri": "spotify:album:0z7pVBGOD7HCIB7S8eLkLI", 
                    "duration_ms": 198800, 
                    "album_name": "In The Zone"
                }, 
 ], 
            "num_edits": 6, 
            "duration_ms": 11532414, 
            "num_artists": 37
        }, 

当我运行程序时，它给出了以下错误：

TypeError Traceback（最近一次调用最后一次） ~\AppData\Local\Temp/ipykernel_3208/3949258436.py 在 16 17 ---> 18 数据= pd.json_normalize(js['playlists'], ['name', 'collaborative', 'pid', 'modified_at', 'num_tracks', 'num_albums', 19 'num_followers'、'tracks'、'num_edits'、'num_artists']、js['info']） 20

~\anaconda3\lib\site-packages\pandas\io\json_normalize.py in _json_normalize(data, record_path, meta, meta_prefix, record_prefix, errors, sep, max_level) 293 294 meta_vals：默认字典=默认字典（列表） --> 295 meta_keys = [sep.join(val) for val in _meta] 296 297 def _recursive_extract（数据，路径，seen_meta，级别=0）：

~\anaconda3\lib\site-packages\pandas\io\json_normalize.py in (.0) 293 294 meta_vals：默认字典=默认字典（列表） --> 295 meta_keys = [sep.join(val) for val in _meta] 296 297 def _recursive_extract（数据，路径，seen_meta，级别=0）：

TypeError: 序列项 0: 预期的 str 实例，找到字典

这是我的代码：

import json
import pandas as pd
import os



path = 'C:\\Users\\sotir\\Desktop\\machinedataset'

filenames = os.listdir(path)
for filename in sorted(filenames):
    if filename.startswith("mpd.slice.") and filename.endswith(".json"):
        fullpath = os.sep.join((path, filename))
        f = open(fullpath)
        js = json.load(f)
        f.close()


data= pd.json_normalize(js['playlists'],  ['name', 'collaborative', 'pid', 'modified_at', 'num_tracks', 'num_albums',
                                                    'num_followers', 'tracks', 'num_edits',  'num_artists'], js['info'])

Answer 1

为了解决您的直接错误，在您的 pd.json.normalize() 调用中，将最后一个 arg 更改为：

['info']

到：

js['info']

你会得到更多的错误，但这是一个新问题的素材。

Answer 2

修改问题的答案：

根据https://pandas.pydata.org/pandas-docs/version/1.2.0/reference/api/pandas.json_normalize.html，pd.json_normalize() 的第三个参数是meta=None

查看该文档页面（您肯定需要查看），我们看到：

pandas.json_normalize
pandas.json_normalize(data, record_path=None, meta=None, meta_prefix=None, record_prefix=None, errors='raise', sep='.', max_level=None)[source]
Normalize semi-structured JSON data into a flat table.

Parameters:
data: dict or list of dicts
    Unserialized JSON objects.

record_path: str or list of str, default None
    Path in each object to list of records. If not passed, data will be assumed to be an array of records.

meta: list of paths (str or list of str), default None
    Fields to use as metadata for each record in resulting table.

根据文档，meta 是一个字符串或字符串列表。您正在传递一个字典，这导致了错误。您需要阅读文档以了解如何调用 json_normalize()