python从json文件中提取密钥不起作用

Question

我是 python 新手，我正在使用 python 3.9.13 尝试从 json 文件中的现有键中提取值。 我知道json.load() 函数输出一个字典，所以在我的代码的最后一部分我在字典中搜索。

这是我的python代码：

import os
import json

with open('./output.json', 'r') as f:
  data = json.load(f)

values= []

if "created" in data:
    print("Key found!")
    print ("Version: ", data["version"], "created at: ", data["created"])
    values.append(data["version"])

print(values)

这是我正在读取的 output.json 文件：

{
  "section1": [
    {
      "name": "name1",
      "version": "1.0.0",
      "description": "",
      "apiVersion": "v2",
      "appVersion": "1.0.22",
      "type": "application",
      "created": "2022-05-03T11:20:45Z"
    },
    {
      "name": "name1",
      "version": "1.0.1",
      "description": "",
      "apiVersion": "v2",
      "appVersion": "1.0.22",
      "type": "application",
      "created": "2022-04-20T13:55:16Z"
    }
  ],
  "section2": [
    {
      "name": "name2",
      "version": "2.0.0",
      "description": "",
      "apiVersion": "v2",
      "appVersion": "1.0.17",
      "type": "application",
      "created": "2022-01-25T07:58:09Z"
    },
    {
      "name": "name2",
      "version": "2.0.1",
      "description": "",
      "apiVersion": "v2",
      "appVersion": "1.0.17",
      "type": "application",
      "created": "2022-01-18T07:08:38Z"
    }
  ]
}

我希望我的数组 values 是：

[1.0.0, 1.0.1, 2.0.0, 2.0.1]

但是我的输出是一个空数组，我不知道为什么。

非常感谢您的帮助！

Answer 1

首先，假设data 是dict 类型，如上所述从JSON 填充：

data = json.load(f)

那么实现所需输出的最简单方法是使用嵌套的list 理解，如下所示：

>>> [dct['version'] for lst in data.values() for dct in lst]
['1.0.0', '1.0.1', '2.0.0', '2.0.1']

请注意，上面的list 理解基本上相当于两个for 循环：

result = []
for lst in data.values():
    for dct in lst:
        result.append(dct['version'])

如果您需要专门检查是否存在 "created" 键，或者如果您需要验证您正在迭代 list 和 dict 类型，例如，您可以改用以下方法：

result = [dct['version'] for lst in data.values() if isinstance(lst, list)
          for dct in lst if isinstance(dct, dict) and 'created' in dct]

Answer 2

您不尊重字典层次结构，当您调用字典中的键时，它不会遍历该字典的所有级别...

这是完成这项工作的代码的更改版本：

import os
import json

with open('./output.json', 'r') as f:
    json_dict = json.load(f)

values= []

for section in json_dict.values():
    for el in section:
        print("Key found!")
        print ("Version: ", el["version"], "created at: ", el["created"])
        values.append(el["version"])

print(values) 

输出：

Key found!
Version:  1.0.0 created at:  2022-05-03T11:20:45Z
Key found!
Version:  1.0.1 created at:  2022-04-20T13:55:16Z
Key found!
Version:  2.0.0 created at:  2022-01-25T07:58:09Z
Key found!
Version:  2.0.1 created at:  2022-01-18T07:08:38Z
['1.0.0', '1.0.1', '2.0.0', '2.0.1']

Answer 3

你的代码可能是这样的：

import os
import json

with open('./output.json', 'r') as f:
  data = json.load(f)

values= []
for section in data:
    for x in range(len(data.values())):
        if "created" in data[section][x]:
            print("Key found!")
            print ("Version: ", data[section][x]["version"], "created at: ", data[section][x]["created"])
            values.append(data[section][x]["version"])

print(values)