基于python 的JSON数据的处理

JSON格式在python 中的使用。

JSON (JavaScript Object Notation) is a popular data format used for representing structured data. It’s common to transmit and receive data between a server and web application in JSON format.

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{
    "firstName": "Jane",
    "lastName": "Doe",
    "hobbies": ["running", "sky diving", "singing"],
    "age": 35,
    "children": [
        {
            "firstName": "Alice",
            "age": 6
        },
        {
            "firstName": "Bob",
            "age": 8
        }
    ]
}

JSON 主要有两种数据结构：

由 key-value对组成的数据结构。这种数据结构在不同的语言中有不同的实现。例如在 Python中是一种 dict 对象；在C语言中是一个struct；在其他语言中，则可能是 record等。
有序集合。这种数据结构在 Python 中对应于列表；在其他语言中，可能对应于 list等。

python JSON to dict

（注意使用string 类型表示 JSON 的方式，使用单引号，双引号，三个引号区分不同）

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import json

person = '{"name": "Bob", "languages": ["English", "Fench"]}'
person_dict = json.loads(person)

# Output: {'name': 'Bob', 'languages': ['English', 'Fench']}
print( person_dict)

# Output: ['English', 'French']
print(person_dict['languages'])

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import json
person_dict = {'name': 'Bob',
'age': 12,
'children': None
}
person_json = json.dumps(person_dict)

# Output: {"name": "Bob", "age": 12, "children": null}
print(person_json)

还有一种写法

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my_json_string = """{
   "article": [

      {
         "id":"01",
         "language": "JSON",
         "edition": "first",
         "author": "Derrick Mwiti"
      },

      {
         "id":"02",
         "language": "Python",
         "edition": "second",
         "author": "Derrick Mwiti"
      }
   ],

   "blog":[
   {
       "name": "Datacamp",
       "URL":"datacamp.com"
   }
   ]
}
"""
to_python = json.loads(my_json_string)

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to_python['blog']
# [{'URL': 'datacamp.com', 'name': 'Datacamp'}]

Python Tuple to JSON Array

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tuple_example = 'Mango', 'Banana', 'Apple';
print(json.dumps(tuple_example));
# ["Mango", "Banana", "Apple"]

Converting JSON to Python Objects

We can parse the above JSON string using json.loads() method from the json module. The result is a Python dictionary.

Converting Python Objects to JSON

Using json.dumps() we can convert Python Objects to JSON.

json.load vs json.loads

json.load is used when loading a file while json.loads(load string) is used when loading a string.

json.dump vs json.dumps

We use json.dump when we want to dump JSON into a file. json.dumps(dump string) is used when we need the JSON data as a string for parsing or printing.

json.dump()方法将JSON写入文件。

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import json

person_dict = {"name": "Bob",
"languages": ["English", "Fench"],
"married": True,
"age": 32
}

with open('person.txt', 'w') as json_file:
  json.dump(person_dict, json_file)

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import json

with open('person.json') as f:
  data = json.load(f)

# Output: {'languages': ['English', 'Fench'], 'name': 'http://china-testing.github.io/'}
print(data)

Format the Result

The example above prints a JSON string, but it is not very easy to read, with no indentations and line breaks.

The json.dumps() method has parameters to make it easier to read the result:

You can also define the separators, default value is (", “, “: “), which means using a comma and a space to separate each object, and a colon and a space to separate keys from values:

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# default choice
json.dumps(x)

格式更加可读

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json.dumps(x, indent=4)

修改了默认的分割符

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json.dumps(x, indent=4, separators=(". ", " = "))

python 格式和json 格式的相互转换

Python	JSON
dict	Object
list	Array
tuple	Array
str	String
int	Number
float	Number
True	true
False	false
None	null

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boolean_value = False
print(json.dumps(boolean_value))
# false

JSON in APIs

Flask provides the jsonify module that will enable us to achieve this.

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from flask import jsonify

@app.route('/_get_current_user')
def get_current_user():
    return jsonify(username=g.user.username,
                   email=g.user.email,
                   id=g.user.id)

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