熊猫json_normalize产生令人困惑的`KeyError`消息？
问题内容：
我正在尝试将嵌套的JSON转换为Pandas数据框。我一直使用json_normalize成功，直到遇到某种JSON。我制作了一个较小的版本来重新创建该问题。
from pandas.io.json import json_normalize
json=[{"events": [{"schedule": {"date": "2015-08-27",
"location": {"building": "BDC", "floor": 5},
"ID": 815},
"group": "A"},
{"schedule": {"date": "2015-08-27",
"location": {"building": "BDC", "floor": 5},
"ID": 816},
"group": "A"}]}]
然后，我运行：
json_normalize(json[0],'events',[['schedule','date'],['schedule','location','building'],['schedule','location','floor']])
期望看到这样的事情：
ID group schedule.date schedule.location.building schedule.location.floor
'815' 'A' '2015-08-27' 'BDC' 5
'816' 'A' '2015-08-27' 'BDC' 5
但是相反我得到了这个错误：
In [2]: json_normalize(json[0],'events',[['schedule','date'],['schedule','location','building'],['schedule','location','floor']])
---------------------------------------------------------------------------
KeyError Traceback (most recent call last)
<ipython-input-2-b588a9e3ef1d> in <module>()
----> 1 json_normalize(json[0],'events',[['schedule','date'],['schedule','location','building'],['schedule','location','floor']])
/Users/logan/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/pandas/io/json.pyc in json_normalize(data, record_path, meta, meta_prefix, record_prefix)
739 records.extend(recs)
740
--> 741 _recursive_extract(data, record_path, {}, level=0)
742
743 result = DataFrame(records)
/Users/logan/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/pandas/io/json.pyc in _recursive_extract(data, path, seen_meta, level)
734 meta_val = seen_meta[key]
735 else:
--> 736 meta_val = _pull_field(obj, val[level:])
737 meta_vals[key].append(meta_val)
738
/Users/logan/Library/Enthought/Canopy_64bit/User/lib/python2.7/site-packages/pandas/io/json.pyc in _pull_field(js, spec)
674 if isinstance(spec, list):
675 for field in spec:
--> 676 result = result[field]
677 else:
678 result = result[spec]
KeyError: 'schedule'
问题答案：
在这种情况下，我认为您只需要使用以下命令：
In [57]: json_normalize(data[0]['events'])
Out[57]:
group schedule.ID schedule.date schedule.location.building \
0 A 815 2015-08-27 BDC
1 A 816 2015-08-27 BDC
schedule.location.floor
0 5
1 5
该meta路径（[['schedule','date']...]）是在同一级别为“事件”嵌套为您的记录，即同级别指定数据。它看起来不太json_normalize适合处理带有嵌套列表的字典，因此，如果实际数据要复杂得多，则可能需要进行一些手动重塑。
