Python，jsonpath:如何正确解析jsonpath？

Question

我有一个实现问题...

#!/usr/bin/python

#This is the API for BTC price request. 
# Average all the amounts, and push that to the program

import json
import urllib.request
from jsonpath_rw import parse as parse_jsonpath

class BtcAPI:

    def __init__(self, url, api_id, json_key):
        self.url = url
        self.api_id = api_id
        self.json_key = json_key

    def btc_api_call(self):

        hdr = { 'User-Agent' : 'Mozilla/5.0 (Windows NT 6.1; Win64; x64)' }
        req = urllib.request.Request(self.url, headers=hdr)
        readdata = urllib.request.urlopen(req)
        json_data = readdata.read()

        json_dict = json.loads(json_data)
        results = parse_jsonpath(self.json_key).find(json_dict)
        print(results)


class Price:


    def __init__(self, api_id, url, json_key):

        self.api_id = api_id
        self.url = url
        self.json_key = json_key

    def pass_for_request(self):

        get_price = BtcAPI(self.url, self.api_id, self.json_key)
        get_price.btc_api_call()


def Coindesk():
    coindesk = Price("coindesk","https://api.coindesk.com/v1/bpi/currentprice.json","time.updated")
coindesk.pass_for_request()

为"json_key“传递的值是"bpi.USD.rate_float"...在此url中。它被传递给一个名为"Price“的类，这个类创建了一些变量，这些变量传递给包含上述代码的类。

coindesk = Price("coindesk","api.coindesk.com/v1/bpi/currentprice.json", "bpi.USD.rate_float")

这就是我的目标json。正在尝试访问rate_float密钥：

{
  "time": {
    "updated": "Feb 5, 2018 18:34:00 UTC",
    "updatedISO": "2018-02-05T18:34:00+00:00",
    "updateduk": "Feb 5, 2018 at 18:34 GMT"
  },
  "disclaimer": "This data was produced from the CoinDesk Bitcoin Price Index (USD). Non-USD currency data converted using hourly conversion rate from openexchangerates.org",
  "chartName": "Bitcoin",
  "bpi": {
    "USD": {
      "code": "USD",
      "symbol": "$",
      "rate": "7,004.9588",
      "description": "United States Dollar",
      "rate_float": 7004.9588
  }
}

当我运行该程序时，它会向我发送整个json文件的输出，而不是我试图通过jsonpath发送给我的特定键，我使用的是jsonpath_rw，使用的是"bpi.USD.rate_float“。

如何使用jsonpath有效地定位rate_float密钥？

Answer 1

问题是，您可能认为results包含来自Python dict的普通字符串值。

这实际上不是jsonpath_rw返回的内容。如果你看一下https://github.com/kennknowles/python-jsonpath-rw中的例子，你会发现它是这样做的，例如

[match.value for match in jsonpath_expr.find({'foo': [{'baz': 1}, {'baz': 2}]})]

正如它提到的那样：

JsonPath.find的结果提供了详细的上下文和路径数据，因此很容易遍历到父对象，打印数据片段的完整路径，并生成自动ids。

find实际上返回一个包含上下文信息的对象列表。如果您想要的只是字符串值，并且您只希望为JSONPath表达式获得一个返回值，则需要执行以下操作：

results = parse_jsonpath(self.json_key).find(json_dict)
print(results[0].value)

Answer 2

下面是一个有效的Python 3方法：

def json_by_jsonpath():
    v_json     = "{\"_id\":{\"oid\":\"55561331552632234577\"},\"profilePatId\":\"123456\",\"patientPatId\":\"123456\",\"comboOrder\":false,\"globalOrderCode\":{\"$numberInt\":\"1\"},\"orderRefNum\":\"621980991862\",\"functionality\":{\"$numberInt\":\"38\"},\"rxType\":{\"$numberInt\":\"1\"},\"orderStoreNum\":\"59382\",\"orderChannel\":\"RR_EM\",\"orderChannelDtls\":\"QULL\",\"scriptDetailRetail\":[{\"rxNum\":{\"$numberInt\":\"274879\"},\"rxStoreNum\":{\"$numberInt\":\"59382\"},\"autoRefillEnabled\":false,\"autoRefillEligible\":false,\"insuranceAvailable\":false,\"sddDrugEligible\":false,\"drugQty\":{\"$numberInt\":\"0\"},\"deliveryInd\":\"1\",\"deliveryComments\":\"Ring bell and drop of in box. This comment is for SDD notes\",\"additionalComments\":\"Please call my insurance and this comment is on notes section\",\"appCode\":{\"$numberInt\":\"291\"}},{\"rxNum\":{\"$numberInt\":\"447902\"},\"rxStoreNum\":{\"$numberInt\":\"59382\"},\"autoRefillEnabled\":false,\"autoRefillEligible\":false,\"insuranceAvailable\":false,\"sddDrugEligible\":false,\"drugQty\":{\"$numberInt\":\"0\"},\"deliveryInd\":\"1\",\"deliveryComments\":\"Ring bell and drop of in box. This comment is for SDD notes\",\"additionalComments\":\"Please call my insurance and this comment is on notes section\",\"appCode\":{\"$numberInt\":\"100\"}}],\"_class\":\"com.rx.repositories.xOrderRetail\"}"


v_jsonpath =  '$._id.oid'  #'$.patientPatId'

        myjson = json.loads(v_json)
    #print(myjson)
    #result_list = [match.value for match in v_jsonpath.find(v_json)]
    #print(result_list)
    json_tag_val = parse(v_jsonpath).find(myjson)
    print(json_tag_val)

    return json_tag_val[0].value