Question

我有以下JSON字典。我想要做的是删除“orbiting_body”不是“地球”的所有“close_approach_data”对象。问题是orbiting_body可能有多个对象：“Earth”，在所有这些对象之间我试图保持最小的“approach_date”。

data = [
  {
    "id": "01",
    "close_approach_data": [
      {
        "orbiting_body": "Earth",
        "approach_date": "1945-06-07"
      },
      {
        "orbiting_body": "Earth",
        "approach_date": "1975-06-07"
      },
      {
        "orbiting_body": "Mars",
        "approach_date": "1935-06-07"
      }
    ]
  },
{
    "id": "02",
    "close_approach_data": [
      {
        "orbiting_body": "Earth",
        "approach_date": "1945-06-07"
      },
      {
        "orbiting_body": "Earth",
        "approach_date": "1975-06-07"
      },
      {
        "orbiting_body": "Mars",
        "approach_date": "1935-06-07"
      }
    ]
  }
]

我希望得到这个：

data = [
  {
    "id": "01",
    "close_approach_data": {
      "orbiting_body": "Mars",
      "approach_date": "1935-06-07"
    }
  },
  {
    "id": "02",
    "close_approach_data": {
      "orbiting_body": "Mars",
      "approach_date": "1935-06-07"
    }
  }
]

所以我想提出一些代码：

earthObjs =[]
for element in data:
    for subel in element["close_approach_data"]:
        if ([subel][0]["orbiting_body"]=="Earth"):
            #then i would have to store the objects
            earthObjs.append([subel])

    #here i am trying to find the object with the min 'approach_date'
    minEarth = min(dt.strptime(earthObjs["close_approach_date"],"%Y-%m-%d"))

    #then i would have to somehow place this as the only element of close_approach_data
    element["close_approach_data"] = json.loads(minEarth)

    #and clear the earthObjs list so it can be used for the next element
    earthObjs.clear()

我非常清楚我的一半代码不起作用。我想我可能最终会接近它的工作，我真的需要一些帮助。具体来说，我知道在搜索min时我做错了，因为我无法访问对象的'close_approach_data'字段。另外，我也不确定json.load s行。

Answer 1

以下是您将描述的处理代码直接转换为代码：

$username =

输出：

from datetime import datetime
import json

for dataset in data:
    earliest, initial = datetime.max, {}

    # Find the non-Earth body with the earliest approach date.
    for close_approach in dataset["close_approach_data"]:
        if close_approach["orbiting_body"] != "Earth":
            dt = datetime.strptime(close_approach["approach_date"],
                                   "%Y-%m-%d")
            if dt < earliest:
                dt, initial = earliest, close_approach

    # Replace entire close_approach_data list with a single object
    # comprised of the non-Earth item with the earliest date (or an
    # empty dictionary if there weren't any).
    dataset["close_approach_data"] = initial

print(json.dumps(data, indent=4))

Answer 2

这是实现算法的一种方法：

res = []

for d in data:
    res.append({**{'id': d['id'], **{'close_approch_data': \
    next((iter(sorted((e for e in d['close_approach_data'] \
                      if e['orbiting_body'] != 'Earth'), \
                     key=lambda x: x['approach_date']))), None)}}})

print(res)

[{'close_approch_data': {'approach_date': '1935-06-07',
                         'orbiting_body': 'Mars'},
  'id': '01'},
 {'close_approch_data': {'approach_date': '1935-06-07',
                         'orbiting_body': 'Mars'},
  'id': '02'}]

<强>解释

乍一看（和第二次），这看起来像一团糟。但关键部分是：

迭代你的词典列表。
对于每个id，请将项目附加到列表res。
仅通过生成器表达式中的if子句包含非来自地球的数据。
按接近日期排序;您可以继续使用datetime，但根据当前格式，这不是必需的。
通过next(iter(...))提取第一个元素（如果它存在）。如果不存在任何元素，请返回{'close_approach_data': None}。

删除除最小日期之外的所有嵌套JSON数组

2 个答案: