如何用 Python 解析嵌套的 Json？

Question

我正在尝试解析这个嵌套的 JSON 文件，但我运行无法获取我需要的每个元素。

这里是 json 例子：

    {
  "sensor-time" : {
    "timezone" : "New_York",
    "time" : "2020-07-15T12:45:02-04:00"
  },
  "status" : {
    "code" : "OK"
  },
  "content" : {
    "element" : [ {
      "element-id" : 0,
      "element-name" : "Line 0",
      "sensor-type" : "SINGLE_SENSOR",
      "data-type" : "LINE",
      "from" : "2020-07-15T12:30:00-04:00",
      "to" : "2020-07-15T12:45:00-04:00",
      "resolution" : "FIVE_MINUTES",
      "measurement" : [ {
        "from" : "2020-07-15T12:30:00-04:00",
        "to" : "2020-07-15T12:35:00-04:00",
        "value" : [ {
          "value" : 1,
          "label" : "fw"
        }, {
          "value" : 2,
          "label" : "bw"
        } ]
      }, {
        "from" : "2020-07-15T12:35:00-04:00",
        "to" : "2020-07-15T12:40:00-04:00",
        "value" : [ {
          "value" : 3,
          "label" : "fw"
        }, {
          "value" : 4,
          "label" : "bw"
        } ]
      }, {
        "from" : "2020-07-15T12:40:00-04:00",
        "to" : "2020-07-15T12:45:00-04:00",
        "value" : [ {
          "value" : 5,
          "label" : "fw"
        }, {
          "value" : 6,
          "label" : "bw"
        } ]
      } ]
    }, {
      "element-id" : 1,
      "element-name" : "Test Line",
      "sensor-type" : "SINGLE_SENSOR",
      "data-type" : "LINE",
      "from" : "2020-07-15T12:30:00-04:00",
      "to" : "2020-07-15T12:45:00-04:00",
      "resolution" : "FIVE_MINUTES",
      "measurement" : [ {
        "from" : "2020-07-15T12:30:00-04:00",
        "to" : "2020-07-15T12:35:00-04:00",
        "value" : [ {
          "value" : 7,
          "label" : "fw"
        }, {
          "value" : 8,
          "label" : "bw"
        } ]
      }, {
        "from" : "2020-07-15T12:35:00-04:00",
        "to" : "2020-07-15T12:40:00-04:00",
        "value" : [ {
          "value" : 9,
          "label" : "fw"
        }, {
          "value" : 10,
          "label" : "bw"
        } ]
      }, {
        "from" : "2020-07-15T12:40:00-04:00",
        "to" : "2020-07-15T12:45:00-04:00",
        "value" : [ {
          "value" : 11,
          "label" : "fw"
        }, {
          "value" : 12,
          "label" : "bw"
        } ]
      } ]
    } ]
  },
  "sensor-info" : {
    "serial-number" : "D7:40:1:7F:4A:72",
    "ip-address" : "192.168.130.44",
    "name" : "DemoNew",
    "group" : "Internal Test Devices",
    "device-type" : "PC2"
  }
}

我想获取的是每个元素名称的测量数据。请看下面的例子：

这是我尝试过的：

    data = {} # element-name ↦ direction ↦ {readings ↦ (timestamp × value) list, meta ↦ name ↦ value}
for element in json_data['content']['element']:
    element_name = element['element-name']
    element_data = {}

# collect
    for measurement in element['measurement']:
        dt = datetime.strptime(measurement['to'][:-3]+'00', '%Y-%m-%dT%H:%M:%S%z')
        t = mktime(dt.timetuple())

        for pair in measurement['value']:
            direction = pair['label']
            value     = pair['value']

            if not direction in element_data: element_data[direction] = []
            element_data[direction].append( (t, value) )

# insert
    metadata = {}
    for key in element:
        if not key in ['measurement', 'from', 'to']:
            metadata[key] = element[key]
    data[element_name] = {}
    for direction in element_data:
        data[element_name][direction] = {'readings': element_data[direction], 'meta': metadata}

camera_metadata = {}
for key in json_data:
    if not key in ['content']:
        camera_metadata[key] = json_data[key]

她就是我得到的结果：

    {'Line 0': {'fw': {'readings': [(1594830900.0, 1),
    (1594831200.0, 3),
    (1594831500.0, 5)],
   'meta': {'element-id': 0,
    'element-name': 'Line 0',
    'sensor-type': 'SINGLE_SENSOR',
    'data-type': 'LINE',
    'resolution': 'FIVE_MINUTES'}},
  'bw': {'readings': [(1594830900.0, 2), (1594831200.0, 4), (1594831500.0, 6)],
   'meta': {'element-id': 0,
    'element-name': 'Line 0',
    'sensor-type': 'SINGLE_SENSOR',
    'data-type': 'LINE',
    'resolution': 'FIVE_MINUTES'}}},
 'GP Test CL.01': {'fw': {'readings': [(1594830900.0, 7),
    (1594831200.0, 9),
    (1594831500.0, 11)],
   'meta': {'element-id': 1,
    'element-name': 'GP Test CL.01',
    'sensor-type': 'SINGLE_SENSOR',
    'data-type': 'LINE',
    'resolution': 'FIVE_MINUTES'}},
  'bw': {'readings': [(1594830900.0, 8),
    (1594831200.0, 10),
    (1594831500.0, 12)],
   'meta': {'element-id': 1,
    'element-name': 'GP Test CL.01',
    'sensor-type': 'SINGLE_SENSOR',
    'data-type': 'LINE',
    'resolution': 'FIVE_MINUTES'}}}}

我需要调整什么才能使结果看起来像上面的屏幕截图示例？

Answer 1

您试图一次获取一部分信息。但是要将 json 解析为数据框，您需要在嵌套循环中完成所有操作。

    result = []
    for element in json_data['content']['element']:
        for m in element['measurement']:
            data = {}
            for val in m['value']:
                data['SERIAL_NUMBER'] = json_data['sensor-info']['serial-number']
                data['IP'] = json_data['sensor-info']['ip-address']
                data['name'] = json_data['sensor-info']['name']
                data['Group'] = json_data['sensor-info']['group']
                data['Device Type'] = json_data['sensor-info']['device-type']
                data['element-id'] = element['element-id']
                data['Line name'] = element['element-name']
                data['From time'] = m['from']
                data['to time'] = m['to']
                data[val['label']] = val['value']
            result.append(data)
    df = pd.DataFrame(result)

输出：

      SERIAL_NUMBER              IP     name                  Group  \
0  D7:40:1:7F:4A:72  192.168.130.44  DemoNew  Internal Test Devices   
1  D7:40:1:7F:4A:72  192.168.130.44  DemoNew  Internal Test Devices   
2  D7:40:1:7F:4A:72  192.168.130.44  DemoNew  Internal Test Devices   
3  D7:40:1:7F:4A:72  192.168.130.44  DemoNew  Internal Test Devices   
4  D7:40:1:7F:4A:72  192.168.130.44  DemoNew  Internal Test Devices   
5  D7:40:1:7F:4A:72  192.168.130.44  DemoNew  Internal Test Devices   

  Device Type  element-id  Line name                  From time  \
0         PC2           0     Line 0  2020-07-15T12:30:00-04:00   
1         PC2           0     Line 0  2020-07-15T12:35:00-04:00   
2         PC2           0     Line 0  2020-07-15T12:40:00-04:00   
3         PC2           1  Test Line  2020-07-15T12:30:00-04:00   
4         PC2           1  Test Line  2020-07-15T12:35:00-04:00   
5         PC2           1  Test Line  2020-07-15T12:40:00-04:00   

                     to time  fw  bw  
0  2020-07-15T12:35:00-04:00   1   2  
1  2020-07-15T12:40:00-04:00   3   4  
2  2020-07-15T12:45:00-04:00   5   6  
3  2020-07-15T12:35:00-04:00   7   8  
4  2020-07-15T12:40:00-04:00   9  10  
5  2020-07-15T12:45:00-04:00  11  12

如您所见，我没有弄清楚您的时间格式。另外，我认为你切换了“组”和“设备类型”。

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