python - 数据库提取出的数据转json

Question

我从数据库中取出两列数据得到

data = [['美国', 46], ['英国', 27], ['中国', 26]]

如何转换为json格式的文件

{
    {
        name: '美国',
        value: 46
    },
    {
        name: '英国',
        value: 27
    },
    {
        name: '中国',
        value: 26
    },
}

求相关的python代码。最好能附上注释，本人初学者，多包涵，真的不是很会这个问题。

Answer 1

I think the result you want may be:

[
    {
        "name": "美国",
        "value": 46
    },
    {
        "name": "英国",
        "value": 27
    },
    {
        "name": "中国",
        "value": 26
    }
]

or:

{
    "data": [
        {
            "name": "美国",
            "value": 46
        },
        {
            "name": "英国",
            "value": 27
        },
        {
            "name": "中国",
            "value": 26
        }
    ]
}

import json


def convert_to_json_string_1(data):
    return json.dumps([{'name': i[0], 'value': i[1]} for i in data], indent=4)
    
def convert_to_json_string_2(data):
    return json.dumps({'data': [{'name': i[0], 'value': i[1]} for i in data]}, indent=4)

The json format actually serializes Python objects into a plain text file (for Python)
json.dumps function converts (serializes) a python object into a json string. Indent means using 4 spaces to indent Enter, this string is also a normal string, you can:

with open('some-file.json', 'w') as handle:
    handle.write(convert_to_json_string_1(data)

For beginners, the above code may not be easy to understand. Let’s write the first function in a more idiotic way:

def convert_to_json_string_1(data):
    ret = []  # 需要序列化的列表
    for i in data:
        tmp = {'name': i[0], 'value': i[1]}  # 通过data的每一个元素构造一个字典
        ret.append(tmp)
    ret = json.dumps(ret, indent=4)
    return ret

Answer 2

About the question

@pylego There is a problem. Your output example is not standard json (for the standard definition of json, please refer to: Introducing JSON). {} is a js object, similar to Python's dictionary. It should be composed of key-value pairs. , the example you gave:

{
    {
        name: '美国',
        value: 46
    },
    {
        name: '英国',
        value: 27
    },
    {
        name: '中国',
        value: 26
    },
}

Obviously not in compliance with the regulations, so guess:

[
    {
        "name": "美国",
        "value": 46
    },
    {
        "name": "英国",
        "value": 27
    },
    {
        "name": "中国",
        "value": 26
    }
]

That’s what you want.

How to do it

import json

data = [['美国', 46], ['英国', 27], ['中国', 26]]
names = 'name value'.split()

data = [dict(zip(names, d)) for d in data]

with open('out.json', 'w') as writer:
    json_data = json.dumps(data, sort_keys=True, indent=4, separators=(',', ': '), ensure_ascii=False) 
    print(json_data, file=writer)

Everyone should have similar methods in terms of practice, which can be roughly divided into three parts:

• Convert data to the desired form: list of dictionary

• Use json module to convert json module 將 data 轉為 json_data to json_data

• Write to file

(1) Convert data to the desired form: list of dictionary

The method of the first part is quite different, I chose to make it first namesThis list:

names = 'name value'.split()

Actually this is similar to:

names = ['name', 'value']

is the same, but I really like using split because it is faster to write (when there are many projects, you don’t need to put so many quotation marks).

Then I use a list comprehension to create a list of dictionary:

data = [dict(zip(names, d)) for d in data]

First use for d in data to iterate over each pair in for d in data 來迭代 data 中的一個一個 pair, 然後使用 zip, and then use zip to combine the project name with the corresponding value:

# zip
'美国',  46
   |     |      =>  ('name', '美国'), ('value', 46)
'name'  'value'

Then dict can take in an iterables (each item is a key-value pair, such as a two-element tuple) and create a dictionary.

(2) Use json module to convert json module 將 data 轉為 json_data to json_data

The second part, transfer out json_data, 這相當容易, 使用 dumps can be done, please refer to json.dumps

json_data = json.dumps(data, sort_keys=True, indent=4, separators=(',', ': '), ensure_ascii=False) 

• sort_keys: 會排序 json 中 object The keys inside can be set or not

• indent: Set indentation

• separators: 設定 json 輸出的分隔符號, ',' 用於分隔項目, ': ' Used to separate keys and values

• ensure_ascii: 設為 False, don’t use unicode escape when printing

(3) Write to file

Nothing special, use with 處理文件開關, 利用 print(file=XXX) output

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Questions I answered: Python-QA