在 python 3 中遍历 JSON 文件

Question

目前我正在尝试从包含日期和国家/地区的 json 文件中获取“严格”数据。以下是 json 输出的摘录：

import pandas as pd
import json
from bs4 import BeautifulSoup

# load file
with open("Stringency April 8.txt") as file:
    stringency_data = json.load(file)

stringency_data["data"]

#this gives the output:

{'2020-01-02': {'ABW': {'confirmed': None,`
   'country_code': 'ABW',
   'date_value': '2020-01-02',
   'deaths': None,
   'stringency': 0,
   'stringency_actual': 0},
  'AFG': {'confirmed': 0,
   'country_code': 'AFG',
   'date_value': '2020-01-02',
   'deaths': 0,
   'stringency': 0,
   'stringency_actual': 0},
  'AGO': {'confirmed': None,
   'country_code': 'AGO',
   'date_value': '2020-01-02',
   'deaths': None,
   'stringency': 0,
   'stringency_actual': 0},
  'AUS': {'confirmed': 0,
   'country_code': 'AUS',
   'date_value': '2020-01-02',
   'deaths': 0,
   'stringency': 7.14,
   'stringency_actual': 7.14},
  'AUT': {'confirmed': 0,
   'country_code': 'AUT',
   'date_value': '2020-01-02',
   'deaths': 0,
   'stringency': 0,
   'stringency_actual': 0},.........

到目前为止，这是我的代码（为了这篇文章，我已经缩短了一点）：

# create empty list for dates

date_index = []
[date_index.append(date) for date in stringency_data["data"]]



#creates empty lists for countries

Australia = []
Austria = []
...
US = []

# put these lists into a list
countries_lists = [Australia, Austria,...US]

# put country codes into a list
country_codes = ["AUS", "AUT",..."USA"]

# loop through countries

i = 0

for country, code in zip(countries_lists, country_codes):
    while i<=len(date_index):
        country.append(stringency_data["data"][date_index[i]][code]["stringency_actual"])
        i+=1

当我打印“澳大利亚”列表时，我得到了我想要的所有值。但是从奥地利开始的任何国家仍然是一个空列表。

我得到输出 - KeyError：“AUS”。这表明代码检索了整个时间序列，但仅针对第一个国家（澳大利亚）。如何为每个国家/地区代码循环？

Answer 1

以下是我对您描述/显示的数据的看法：

file data is a dictionary; single known/desired key is "data", value is a dictionary.
--> keys are all date_strings.  Each value is a dictionary.
-----> keys are all country_codes.  Each value is a dictionary.
--------> a key "stringency_actual" is present, and its value is desired.

因此，获取这些数据的简单计划可能如下所示：

1. grab file['data']
2. iterate all keys and values in this dictionary.  (Actually, you may only care about the values.)
3. iterate all keys and values in this dictionary.  Keys are country_codes, which tell you to which list you want to append the stringency_actual value you're about to get.
4. grab this dictionary['stringency_actual'] and append it to the list corresponding to the correct country.
4b. translate the country_code to the country_name, since that's apparently how you would like to store this data for now.

我更改了数据检索，因为数据都是字典，因此它可以通过其键进行自我描述。这样做可以帮助防止我在原始问题和评论中看到的 KeyError 。 （如果没有完整的输入文件或 KeyError 的行号，我认为我们都无法 100% 确定输入中的哪个值导致了该 KeyError。）

可能的答案：

import json

# Input sample data; would actually be retrieved from file.
stringency_data = json.loads("""
{"data": {"2020-01-02": {"ABW": {"confirmed": null,
   "country_code": "ABW",
   "date_value": "2020-01-02",
   "deaths": null,
   "stringency": 0,
   "stringency_actual": 0},
  "AFG": {"confirmed": 0,
   "country_code": "AFG",
   "date_value": "2020-01-02",
   "deaths": 0,
   "stringency": 0,
   "stringency_actual": 0},
  "AGO": {"confirmed": null,
   "country_code": "AGO",
   "date_value": "2020-01-02",
   "deaths": null,
   "stringency": 0,
   "stringency_actual": 0},
  "AUS": {"confirmed": 0,
   "country_code": "AUS",
   "date_value": "2020-01-02",
   "deaths": 0,
   "stringency": 7.14,
   "stringency_actual": 7.14},
  "AUT": {"confirmed": 0,
   "country_code": "AUT",
   "date_value": "2020-01-02",
   "deaths": 0,
   "stringency": 0,
   "stringency_actual": 0}}}
}""")

country_name_by_code = {
    'ABW': 'Aruba',
    'AFG': 'Afghanistan',
    'AUS': 'Australia',
    'AUT': 'Austria',
#    ...
    'USA': 'United States'
}

# Output data we want to create
actual_stringencies_by_country_name = {}


# Helper method to store data we're interested in
def append_country_stringency(country_code, actual_stringency_value):
    if country_code not in country_name_by_code:
        print(f'Unknown country_code value "{country_code}"; ignoring.')
        return

    country_name = country_name_by_code[country_code]

    if country_name not in actual_stringencies_by_country_name:
        actual_stringencies_by_country_name[country_name] = []

    actual_stringencies_by_country_name[country_name].append(actual_stringency_value)


# Walk our input data and store the parts we're looking for
for date_string, data_this_date in stringency_data['data'].items():
    for country_code, country_data in data_this_date.items():
        append_country_stringency(country_code, country_data['stringency_actual'])

print(actual_stringencies_by_country_name)

我的输出：

C:\some_dir>python test.py
Unknown country_code value "AGO"; ignoring.
{'Aruba': [0], 'Afghanistan': [0], 'Australia': [7.14], 'Austria': [0]}