Unhashable 類型：在 pymongo 中使用 push 時的“list”

Question

我目前正在從事 web 抓取項目。 目標是每天檢索加油站 (900+) 中可用的不同類型燃料的價格。 如果價格發生變化，腳本就能將 append 的新價格添加到我的 Mongodb 數據庫中。

收集的數據如下所示：

Price_post_api = {

    "station_id": 31200009,
    "price_detail": [
      {
        "fuel_id": 1,
        "fuel_name": "Gazole",
        "fuel_cost": 1.959,
        "update_date": {
          "$date": "2022-05-30T10:05:22Z"
        }
      },
      {
        "fuel_id": 2,
        "fuel_name": "SP95",
        "fuel_cost": 2.049,
        "update_date": {
          "$date": "2022-05-30T10:05:23Z"
        }
      },
      {
        "fuel_id": 5,
        "fuel_name": "E10",
        "fuel_cost": 2.009,
        "update_date": {
          "$date": "2022-05-30T10:05:23Z"
        }
      }
    ]
  },

我很難弄清楚如何根據"fuel_cost"字段正確$push Mongodb 中的數據。 這里是 db 中預期的 output 的示例。

Mongodb_price_data ={
    "station_id": 31200009,
    "price_detail": [
      {
        "fuel_id": 1,
        "fuel_name": "Gazole",
        "fuel_cost": 1.959,
        "update_date": {
          "$date": "2022-05-30T10:05:22Z"
        }
      },
      {
        "fuel_id": 1,
        "fuel_name": "Gazole",
        "fuel_cost": 35.87,
        "update_date": {
          "$date": "2022-05-31T10:09:22Z"
        }
      },
      {
        "fuel_id": 2,
        "fuel_name": "SP95",
        "fuel_cost": 2.049,
        "update_date": {
          "$date": "2022-05-30T10:05:23Z"
        }
      },
      {
        "fuel_id": 2,
        "fuel_name": "Gazole",
        "fuel_cost": 1.59,
        "update_date": {
          "$date": "2022-07-14T00:10:19Z"
        }
      },
      {
        "fuel_id": 5,
        "fuel_name": "E10",
        "fuel_cost": 2.009,
        "update_date": {
          "$date": "2022-05-30T10:05:23Z"
        }
      }
    ]
}

到目前為止，我已經創建了以下 function：

def update_new_price(station_id, fuel_id, fuel_name, cost):
    query = {'station_id':station_id, 'price_detail.fuel_id':fuel_id, 'price_detail.fuel_name':fuel_name,'price_detail.fuel_cost':cost}
    new_value = {
        '$push':{
            'price_detail':{
                [{'price_detail.fuel_id': fuel_id,'price_detail.fuel_name':fuel_name ,'price_detail.fuel_cost':cost}]
            }}}
    result = db[CL_PRICE].find(query)
    if not list(result):
        db[CL_PRICE].update_one(query,new_value,upsert= True)
        print('new value added')
    else:
        print('Already exists')

一旦我運行我的代碼，我就會收到一條錯誤消息。

  'price_detail':{
TypeError: unhashable type: 'list'

知道為什么以及如何解決它嗎？

Answer 1

我認為你需要在那里移除額外的彎曲支架。

代替

            'price_detail':{
                [{'price_detail.fuel_id': fuel_id,'price_detail.fuel_name':fuel_name ,'price_detail.fuel_cost':cost}]
            }

應該是

            'price_detail': [
                {'price_detail.fuel_id': fuel_id,'price_detail.fuel_name':fuel_name ,'price_detail.fuel_cost':cost}
            ]

您實際上是在嘗試創建一個由單個元素組成的集合，該元素是一個列表。 並且 set 只能包含列表不是的可散列對象。

一個最小的可重現示例是

>>> {[1, 2, 3]}
Traceback (most recent call last):
  Input In [2] in <cell line: 1>
    {[1, 2, 3]}
TypeError: unhashable type: 'list'

中間沒有:的{}是創建集合的語法。 為清楚起見，以下是一些創建集合的正確方法的示例。

>>> {(1, 2, 3)}  # a set containing a single tuple
{(1, 2, 3)}
>>> {*[1, 2, 3]}  # a set of three elements created from a list
{1, 2, 3}
>>> {1, 2, 3}  # a set created from three values
{1, 2, 3}
>>> {x for x in range(1, 4)}  # a set comprehension expression
{1, 2, 3}