译（三十六）-Python读取json数据

MWHLS • 2021/11/27 am9:26 • Python, 计算机语言

已阅： 47

stackoverflow热门问题目录
如有翻译问题欢迎评论指出，谢谢。

为什么 Python 无法解释 json 数据？

Why can\'t Python parse this JSON data?

为什么 Python 无法解释 json 数据？

michele asked:

文件里面有 json 如下：

{
"maps": [
    {
        "id": "blabla",
        "iscategorical": "0"
    },
    {
        "id": "blabla",
        "iscategorical": "0"
    }
],
"masks": [
    "id": "valore"
],
"om_points": "value",
"parameters": [
    "id": "valore"
]
}

然后我写了脚本来打印所有 json 数据：

import json
from pprint import pprint
with open('data.json') as f:
data = json.load(f)
pprint(data)

但程序报错了：

Traceback (most recent call last):
File "", line 5, in 
data = json.load(f)
File "/usr/lib/python3.5/json/__init__.py", line 319, in loads
return _default_decoder.decode(s)
File "/usr/lib/python3.5/json/decoder.py", line 339, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
File "/usr/lib/python3.5/json/decoder.py", line 355, in raw_decode
obj, end = self.scan_once(s, idx)
json.decoder.JSONDecodeError: Expecting ',' delimiter: line 13 column 13 (char 213)

怎么才能解释 json，并从中取值？

Answers:
- Justin Peel - vote: 2187
- 这串数据并不是有效的 JSON 格式，有的 [] 应该是 {} ：
  - [] 是 json 数组，对应 Python 的 list
  - {} 是 json 对象，对应 Python 的 dict
- 正确的 json 应该是这样的：
- ```
{
  "maps": [
      {
          "id": "blabla",
          "iscategorical": "0"
      },
      {
          "id": "blabla",
          "iscategorical": "0"
      }
  ],
  "masks": {
      "id": "valore"
  },
  "om_points": "value",
  "parameters": {
      "id": "valore"
  }
}
```
- 然后是代码：
- ```
  import json
  from pprint import pprint
  with open('data.json') as f:
      data = json.load(f)
  pprint(data)
```
- 对于这些数据，可以这样获取值：
- ```
data["maps"][0]["id"]
data["masks"]["id"]
data["om_points"]
```
- 试试，看看是不是正常了。
- Bengt - vote: 320
  - data.json 应该是这样的：
  - ```
  {
  "maps":[
       {"id":"blabla","iscategorical":"0"},
       {"id":"blabla","iscategorical":"0"}
      ],
  "masks":
       {"id":"valore"},
  "om_points":"value",
  "parameters":
       {"id":"valore"}
  }
```
- 代码应该是这样的：
- ```
import json
from pprint import pprint
with open('data.json') as data_file:    
data = json.load(data_file)
pprint(data)
```
  - 注意这只在 Python 2.6 及以上版本可用，因为它依赖于 with 。在 Python 2.5 使用 from __future__ import with_statement ，对于 Python 2.4 以下的版本，见 Justin Peel 的回答。
  - 这样可以获取单个值：
  - ```
  data["maps"][0]["id"]  # will return 'blabla'
  data["masks"]["id"]    # will return 'valore'
  data["om_points"]      # will return 'value'
```
- Geng Jiawen - vote: 76
  - Justin Peel 的回答很有效，不过如果在 Python 3 中读取 json 的话，可以这样：
  - ```
  with open('data.json', encoding='utf-8') as data_file:
  data = json.loads(data_file.read())
```
- 注意：使用 json.loads 代替 json.load 。在 Python 3 中，json.loads 传入字符串参数。json.load 传入类文件对象参数。 data_file.read() 返回字符串对象。
- 实话说，我不觉得大多数情况下读取整个 json 数据会有问题。我在 JS、Java、Kotlin、cpp、rust 都试过。考虑内存问题对我来说就像个笑话 🙂
- 换句话说，我不认为你能在不完全读取它的情况下解释 json 数据。

Why can\'t Python parse this JSON data?

michele asked:

I have this JSON in a file:
文件里面有 json 如下：

{
"maps": [
    {
        "id": "blabla",
        "iscategorical": "0"
    },
    {
        "id": "blabla",
        "iscategorical": "0"
    }
],
"masks": [
    "id": "valore"
],
"om_points": "value",
"parameters": [
    "id": "valore"
]
}

I wrote this script to print all of the JSON data:
然后我写了脚本来打印所有 json 数据：

import json
from pprint import pprint
with open('data.json') as f:
data = json.load(f)
pprint(data)

This program raises an exception, though:
但程序报错了：

Traceback (most recent call last):
File "", line 5, in 
data = json.load(f)
File "/usr/lib/python3.5/json/__init__.py", line 319, in loads
return _default_decoder.decode(s)
File "/usr/lib/python3.5/json/decoder.py", line 339, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
File "/usr/lib/python3.5/json/decoder.py", line 355, in raw_decode
obj, end = self.scan_once(s, idx)
json.decoder.JSONDecodeError: Expecting ',' delimiter: line 13 column 13 (char 213)

How can I parse the JSON and extract its values?
怎么才能解释 json，并从中取值？

Answers:
- Justin Peel - vote: 2187
- Your data is not valid JSON format. You have [] when you should have {}:
  这串数据并不是有效的 JSON 格式，有的 [] 应该是 {} ：
  - [] are for JSON arrays, which are called list in Python
    [] 是 json 数组，对应 Python 的 list
  - {} are for JSON objects, which are called dict in Python
    {} 是 json 对象，对应 Python 的 dict
- Here\'s how your JSON file should look:
  正确的 json 应该是这样的：
- ```
{
  "maps": [
      {
          "id": "blabla",
          "iscategorical": "0"
      },
      {
          "id": "blabla",
          "iscategorical": "0"
      }
  ],
  "masks": {
      "id": "valore"
  },
  "om_points": "value",
  "parameters": {
      "id": "valore"
  }
}
```
- Then you can use your code:
  然后是代码：
- ```
import json
from pprint import pprint
with open('data.json') as f:
  data = json.load(f)
pprint(data)
```
- With data, you can now also find values like so:
  对于这些数据，可以这样获取值：
- ```
data["maps"][0]["id"]
data["masks"]["id"]
data["om_points"]
```
- Try those out and see if it starts to make sense.
  试试，看看是不是正常了。
- Bengt - vote: 320
  - Your data.json should look like this:
    data.json 应该是这样的：
  - ```
  {
  "maps":[
       {"id":"blabla","iscategorical":"0"},
       {"id":"blabla","iscategorical":"0"}
      ],
  "masks":
       {"id":"valore"},
  "om_points":"value",
  "parameters":
       {"id":"valore"}
  }
```
- Your code should be:
  代码应该是这样的：
- ```
import json
from pprint import pprint
with open('data.json') as data_file:    
data = json.load(data_file)
pprint(data)
```
  - Note that this only works in Python 2.6 and up, as it depends upon the with-statement. In Python 2.5 use from __future__ import with_statement, in Python <= 2.4, see Justin Peel\'s answer, which this answer is based upon.
    注意这只在 Python 2.6 及以上版本可用，因为它依赖于 with 。在 Python 2.5 使用 from __future__ import with_statement ，对于 Python 2.4 以下的版本，见 Justin Peel 的回答。
  - You can now also access single values like this:
    这样可以获取单个值：
  - ```
  data["maps"][0]["id"]  # will return 'blabla'
  data["masks"]["id"]    # will return 'valore'
  data["om_points"]      # will return 'value'
```
- Geng Jiawen - vote: 76
  - Justin Peel\'s answer is really helpful, but if you are using Python 3 reading JSON should be done like this:
    Justin Peel 的回答很有效，不过如果在 Python 3 中读取 json 的话，可以这样：
  - ```
  with open('data.json', encoding='utf-8') as data_file:
  data = json.loads(data_file.read())
```
- Note: use json.loads instead of json.load. In Python 3, json.loads takes a string parameter. json.load takes a file-like object parameter. data_file.read() returns a string object.
  注意：使用 json.loads 代替 json.load 。在 Python 3 中，json.loads 传入字符串参数。json.load 传入类文件对象参数。 data_file.read() 返回字符串对象。
- To be honest, I don\'t think it\'s a problem to load all json data into memory in most cases.I see this in JS, Java, Kotlin, cpp, rust almost every language I use.Consider memory issue like a joke to me 🙂
  实话说，我不觉得大多数情况下读取整个 json 数据会有问题。我在 JS、Java、Kotlin、cpp、rust 都试过。考虑内存问题对我来说就像个笑话 🙂
- On the other hand, I don\'t think you can parse json without reading all of it.
  换句话说，我不认为你能在不完全读取它的情况下解释 json 数据。