尝试从JSON fi计算数组中的项数

2024-04-26 23:39:16 发布

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我有一个用rpi创建的json文件（见下文），我在查看数组中的项数（在这个例子中，我在查看hex出现的次数）

JSON文件

{
    "now": 1558947116.6,
    "messages": 44571282,
    "aircraft": [{
            "hex": "405658",
            "alt_baro": 6775,
            "ias": 219,
            "mach": 0.376,
            "mag_heading": 75.4,
            "baro_rate": -1216,
            "geom_rate": -1344,
            "squawk": "0405",
            "mlat": [],
            "tisb": [],
            "messages": 48,
            "seen": 0.1,
            "rssi": -18.0
        }, {
            "hex": "4072a0",
            "flight": "BEE7TL ",
            "alt_baro": 23975,
            "gs": 278.0,
            "ias": 206,
            "tas": 302,
            "mach": 0.488,
            "track": 334.0,
            "roll": -0.4,
            "mag_heading": 320.6,
            "baro_rate": 1184,
            "geom_rate": 928,
            "squawk": "1440",
            "nav_altitude": 24000,
            "mlat": [],
            "tisb": [],
            "messages": 195,
            "seen": 0.1,
            "rssi": -19.1
        }, {
            "hex": "400a5b",
            "flight": "SHT17Q ",
            "alt_baro": 37000,
            "alt_geom": 36825,
            "gs": 460.6,
            "ias": 252,
            "tas": 450,
            "mach": 0.780,
            "track": 155.8,
            "track_rate": -0.03,
            "roll": -0.2,
            "mag_heading": 163.7,
            "baro_rate": 160,
            "geom_rate": 64,
            "squawk": "4464",
            "category": "A0",
            "nav_qnh": 1006.0,
            "nav_altitude": 37008,
            "lat": 53.376617,
            "lon": -2.895996,
            "nic": 8,
            "rc": 186,
            "seen_pos": 0.1,
            "version": 0,
            "nac_v": 2,
            "mlat": [],
            "tisb": [],
            "messages": 1949,
            "seen": 0.1,
            "rssi": -12.4
        }, {
            "hex": "a895eb",
            "flight": "UAL940 ",
            "alt_baro": 35000,
            "alt_geom": 34925,
            "gs": 530.7,
            "ias": 281,
            "tas": 476,
            "mach": 0.824,
            "track": 104.8,
            "track_rate": 0.03,
            "roll": 0.5,
            "mag_heading": 110.4,
            "baro_rate": 0,
            "geom_rate": 0,
            "squawk": "6323",
            "emergency": "none",
            "category": "A5",
            "nav_qnh": 1013.6,
            "nav_altitude": 35008,
            "nav_heading": 106.9,
            "lat": 53.059915,
            "lon": -2.493426,
            "nic": 8,
            "rc": 186,
            "seen_pos": 0.9,
            "version": 2,
            "nic_baro": 1,
            "nac_p": 9,
            "nac_v": 1,
            "sil": 3,
            "sil_type": "perhour",
            "gva": 2,
            "sda": 2,
            "mlat": [],
            "tisb": [],
            "messages": 5093,
            "seen": 0.1,
            "rssi": -3.8
        }, {
            "hex": "4074b4",
            "flight": "EZY93QG ",
            "alt_baro": 34000,
            "alt_geom": 34100,
            "gs": 410.4,
            "ias": 259,
            "tas": 430,
            "mach": 0.748,
            "track": 322.8,
            "track_rate": 0.00,
            "roll": 0.0,
            "mag_heading": 315.4,
            "baro_rate": 0,
            "geom_rate": 32,
            "squawk": "2720",
            "emergency": "none",
            "category": "A3",
            "nav_qnh": 1013.6,
            "nav_altitude": 34016,
            "nav_heading": 0.0,
            "lat": 52.728137,
            "lon": -1.090864,
            "nic": 8,
            "rc": 186,
            "seen_pos": 0.2,
            "version": 2,
            "nic_baro": 1,
            "nac_p": 9,
            "nac_v": 1,
            "sil": 3,
            "sil_type": "perhour",
            "gva": 2,
            "sda": 2,
            "mlat": [],
            "tisb": [],
            "messages": 4134,
            "seen": 0.1,
            "rssi": -10.3
        }, {
            "hex": "4ca4ed",
            "alt_baro": 38000,
            "gs": 394.2,
            "track": 285.4,
            "baro_rate": 832,
            "lat": 51.823487,
            "lon": -2.558136,
            "nic": 0,
            "rc": 0,
            "seen_pos": 45.6,
            "nac_v": 0,
            "mlat": ["gs", "track", "baro_rate", "lat", "lon", "nic", "rc", "nac_v"],
            "tisb": [],
            "messages": 95,
            "seen": 1.3,
            "rssi": -21.6
        }, {
            "hex": "406a99",
            "alt_baro": 9000,
            "squawk": "6357",
            "lat": 51.813538,
            "lon": -2.090075,
            "nic": 9,
            "rc": 75,
            "seen_pos": 55.6,
            "version": 2,
            "sil_type": "perhour",
            "mlat": [],
            "tisb": [],
            "messages": 559,
            "seen": 49.2,
            "rssi": -22.1
        }, {
            "hex": "710111",
            "mlat": [],
            "tisb": [],
            "messages": 49,
            "seen": 257.5,
            "rssi": -23.3
        }, {
            "hex": "392aef",
            "flight": "AFR1669 ",
            "alt_baro": 20750,
            "alt_geom": 20675,
            "gs": 430.0,
            "ias": 302,
            "tas": 408,
            "mach": 0.664,
            "track": 143.8,
            "track_rate": 0.00,
            "roll": 0.0,
            "mag_heading": 151.7,
            "baro_rate": 2112,
            "geom_rate": 2048,
            "squawk": "6301",
            "category": "A0",
            "nav_qnh": 1009.0,
            "nav_altitude": 31008,
            "lat": 52.662918,
            "lon": -2.054367,
            "nic": 7,
            "rc": 371,
            "seen_pos": 0.3,
            "version": 0,
            "nac_v": 2,
            "mlat": [],
            "tisb": [],
            "messages": 7400,
            "seen": 0.0,
            "rssi": -12.2
        }, {
            "hex": "400cee",
            "mlat": [],
            "tisb": [],
            "messages": 114,
            "seen": 91.0,
            "rssi": -22.6
        }
    }
}

Tags： ratetrackaltmessageshexseenrssinic
3条回答
网友
1楼 · 编辑于 2024-04-26 23:39:16

一个简单的解决方案是将JSON转换成String，然后使用.count()方法计算'hex'的频率

import json

data = {
  "now": 1558947116.6,
  "messages": 44571282,
  "aircraft": [
    {
      "hex": "405658",
      "alt_baro": 6775,
      "ias": 219,
      "mach": 0.376,
      "mag_heading": 75.4,
      "baro_rate": -1216,
      "geom_rate": -1344,
      "squawk": "0405",
      "mlat": [],
      "tisb": [],
      "messages": 48,
      "seen": 0.1,
      "rssi": -18.0
    },
    {
      "hex": "4072a0",
      "flight": "BEE7TL ",
      "alt_baro": 23975,
      "gs": 278.0,
      "ias": 206,
      "tas": 302,
      "mach": 0.488,
      "track": 334.0,
      "roll": -0.4,
      "mag_heading": 320.6,
      "baro_rate": 1184,
      "geom_rate": 928,
      "squawk": "1440",
      "nav_altitude": 24000,
      "mlat": [],
      "tisb": [],
      "messages": 195,
      "seen": 0.1,
      "rssi": -19.1
    },
    {
      "hex": "400a5b",
      "flight": "SHT17Q ",
      "alt_baro": 37000,
      "alt_geom": 36825,
      "gs": 460.6,
      "ias": 252,
      "tas": 450,
      "mach": 0.780,
      "track": 155.8,
      "track_rate": -0.03,
      "roll": -0.2,
      "mag_heading": 163.7,
      "baro_rate": 160,
      "geom_rate": 64,
      "squawk": "4464",
      "category": "A0",
      "nav_qnh": 1006.0,
      "nav_altitude": 37008,
      "lat": 53.376617,
      "lon": -2.895996,
      "nic": 8,
      "rc": 186,
      "seen_pos": 0.1,
      "version": 0,
      "nac_v": 2,
      "mlat": [],
      "tisb": [],
      "messages": 1949,
      "seen": 0.1,
      "rssi": -12.4
    },
    {
      "hex": "a895eb",
      "flight": "UAL940 ",
      "alt_baro": 35000,
      "alt_geom": 34925,
      "gs": 530.7,
      "ias": 281,
      "tas": 476,
      "mach": 0.824,
      "track": 104.8,
      "track_rate": 0.03,
      "roll": 0.5,
      "mag_heading": 110.4,
      "baro_rate": 0,
      "geom_rate": 0,
      "squawk": "6323",
      "emergency": "none",
      "category": "A5",
      "nav_qnh": 1013.6,
      "nav_altitude": 35008,
      "nav_heading": 106.9,
      "lat": 53.059915,
      "lon": -2.493426,
      "nic": 8,
      "rc": 186,
      "seen_pos": 0.9,
      "version": 2,
      "nic_baro": 1,
      "nac_p": 9,
      "nac_v": 1,
      "sil": 3,
      "sil_type": "perhour",
      "gva": 2,
      "sda": 2,
      "mlat": [],
      "tisb": [],
      "messages": 5093,
      "seen": 0.1,
      "rssi": -3.8
    },
    {
      "hex": "4074b4",
      "flight": "EZY93QG ",
      "alt_baro": 34000,
      "alt_geom": 34100,
      "gs": 410.4,
      "ias": 259,
      "tas": 430,
      "mach": 0.748,
      "track": 322.8,
      "track_rate": 0.00,
      "roll": 0.0,
      "mag_heading": 315.4,
      "baro_rate": 0,
      "geom_rate": 32,
      "squawk": "2720",
      "emergency": "none",
      "category": "A3",
      "nav_qnh": 1013.6,
      "nav_altitude": 34016,
      "nav_heading": 0.0,
      "lat": 52.728137,
      "lon": -1.090864,
      "nic": 8,
      "rc": 186,
      "seen_pos": 0.2,
      "version": 2,
      "nic_baro": 1,
      "nac_p": 9,
      "nac_v": 1,
      "sil": 3,
      "sil_type": "perhour",
      "gva": 2,
      "sda": 2,
      "mlat": [],
      "tisb": [],
      "messages": 4134,
      "seen": 0.1,
      "rssi": -10.3
    },
    {
      "hex": "4ca4ed",
      "alt_baro": 38000,
      "gs": 394.2,
      "track": 285.4,
      "baro_rate": 832,
      "lat": 51.823487,
      "lon": -2.558136,
      "nic": 0,
      "rc": 0,
      "seen_pos": 45.6,
      "nac_v": 0,
      "mlat": [
        "gs",
        "track",
        "baro_rate",
        "lat",
        "lon",
        "nic",
        "rc",
        "nac_v"
      ],
      "tisb": [],
      "messages": 95,
      "seen": 1.3,
      "rssi": -21.6
    },
    {
      "hex": "406a99",
      "alt_baro": 9000,
      "squawk": "6357",
      "lat": 51.813538,
      "lon": -2.090075,
      "nic": 9,
      "rc": 75,
      "seen_pos": 55.6,
      "version": 2,
      "sil_type": "perhour",
      "mlat": [],
      "tisb": [],
      "messages": 559,
      "seen": 49.2,
      "rssi": -22.1
    },
    {
      "hex": "710111",
      "mlat": [],
      "tisb": [],
      "messages": 49,
      "seen": 257.5,
      "rssi": -23.3
    },
    {
      "hex": "392aef",
      "flight": "AFR1669 ",
      "alt_baro": 20750,
      "alt_geom": 20675,
      "gs": 430.0,
      "ias": 302,
      "tas": 408,
      "mach": 0.664,
      "track": 143.8,
      "track_rate": 0.00,
      "roll": 0.0,
      "mag_heading": 151.7,
      "baro_rate": 2112,
      "geom_rate": 2048,
      "squawk": "6301",
      "category": "A0",
      "nav_qnh": 1009.0,
      "nav_altitude": 31008,
      "lat": 52.662918,
      "lon": -2.054367,
      "nic": 7,
      "rc": 371,
      "seen_pos": 0.3,
      "version": 0,
      "nac_v": 2,
      "mlat": [],
      "tisb": [],
      "messages": 7400,
      "seen": 0.0,
      "rssi": -12.2
    },
    {
      "hex": "400cee",
      "mlat": [],
      "tisb": [],
      "messages": 114,
      "seen": 91.0,
      "rssi": -22.6
    }
  ]
}

data = json.dumps(data)     # Convert JSON to String

hex_count = data.count('hex')       # Count Frequency of 'hex'
网友
2楼 · 编辑于 2024-04-26 23:39:16

如果使用json模块加载文件，则可以迭代aircraft列表中的条目，并计算hex在字典中的次数：

import json

with open('yourfile.json') as fh: # open the file
    data = json.load(fh) # load it into memory as dictionary

hexes = 0 # initialize this at 0 to avoid NameErrors

for craft in data['aircraft']: # iterate over the entries
    if 'hex' in craft: # check for key in dictionary
        hexes += 1 # if that key exists, it will increment hexes

hexes
# 10

或者，更简洁地说，您可以将列表理解与sum结合使用：

hexes = sum([1 for craft in data['aircraft'] if 'hex' in craft])

在这里你会得到一个list的1，对于每个包含键'hex'的工艺，你只需要sum这个结果

网友
3楼 · 编辑于 2024-04-26 23:39:16

您可以使用加载的json向计数器中添加：

count = 0
datastore = json.loads(json_string)
for air in datastore['aircraft']:
    if 'hex' in air:
        count += 1

print(count)

或者使用带lamda的过滤器进行检查，然后得到长度

d = json.loads(json_string)
aircrafts = d['aircraft']
count1 = len(list(filter(lambda x: 'hex' in x, aircrafts)))
print(count1)

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