1 JSON

JSON (javaScript Object Notation) is a lightweight data-interchange format. It is easy for humans to read and write. It is easy for machines to parse and generate. It is based on a subset of the Javascript PRogramming Language, Standard ECMA-262 3rd Edition - December 1999. JSON is a text format that is completely language independent but uses conventions that are familiar to programmers of the C-family of languages, including C, C++, C#, Java, JavaScript, Perl, Python, and many others. These properties make JSON an ideal data-interchange language.

JSON is built on two structures:

These are universal data structures. Virtually all modern programming languages support them in one form or another. It makes sense that a data format that is interchangeable with programming languages also be based on these structures.

In JSON, they take on these forms:

An object is an unordered set of name/value pairs. An object begins with { (left brace)and ends with } (right brace). Each name is followed by : (colon) and the name/value pairs are separated by , (comma).

An array is an ordered collection of values. An array begins with [ (left bracket) and ends with ] (right bracket). Values are separated by , (comma).

A value can be a string in double quotes, or a number, or true or false or null, or anobject or an array. These structures can be nested.

A string is a sequence of zero or more Unicode characters, wrapped in double quotes, using backslash escapes. A character is represented as a single character string. A string is very much like a C or Java string.

A number is very much like a C or Java number, except that the octal and hexadecimal formats are not used.

Whitespace can be inserted between any pair of tokens. Excepting a few encoding details, that completely describes the language.

参考：http://json.org/

JSON 语法规则

JSON 语法是 JavaScript 对象表示法语法的子集。

JSON 名称/值对

JSON 数据的书写格式是：名称/值对。

名称/值对包括字段名称（在双引号中），后面写一个冒号，然后是值：

"firstName" : "John"
这很容易理解，等价于这条 JavaScript 语句：
firstName = "John"
JSON 值
JSON 值可以是：
数字（整数或浮点数）字符串（在双引号中）逻辑值（true 或 false）数组（在方括号中）对象（在花括号中）null
JSON 对象
JSON 对象在花括号中书写：
对象可以包含多个名称/值对：
{ "firstName":"John" , "lastName":"Doe" }
这一点也容易理解，与这条 JavaScript 语句等价：
firstName = "John"lastName = "Doe"
JSON 数组
JSON 数组在方括号中书写：
数组可包含多个对象：
{"employees": [{ "firstName":"John" , "lastName":"Doe" },{ "firstName":"Anna" , "lastName":"Smith" },{ "firstName":"Peter" , "lastName":"Jones" }]}
在上面的例子中，对象 "employees" 是包含三个对象的数组。每个对象代表一条关于某人（有姓和名）的记录。
JSON 文件
JSON 文件的文件类型是 ".json"JSON 文本的 MIME 类型是 "application/json"
参考：http://www.runoob.com/json/json-tutorial.html
2 Python JSON
两个主要的函数是 json.dumps() 和 json.loads()
3 实例
3.1 json.dumps
在做HTTP API开发时，通过REST Client下发POST请求，请求的Payload为：
{    "target_ip": "192.168.16.120",    "kwargs": {        "server_ip": "192.168.111.117"    }}HTTP请求的自定义Header是：
Accept	application/json	  Content-Type	application/json
当程序收到Payload后，打印结果与入库后的结果都是Unicode串：
{'target_ip': u'192.168.16.120', 'kwargs': {u'server_ip': u'192.168.111.111'}}
但是要在库中存非Unicode串，怎么做？
用json.dumps来转换字符串，转换后输出：
{"target_ip": "192.168.16.120", "kwargs": {"server_ip": "192.168.111.111"}用python执行：
>>> import json>>> data = [ { 'a' : 1, 'b' : 2, 'c' : 3, 'd' : 4, 'e' : 5 } ]>>> json.dumps(data)'[{"a": 1, "c": 3, "b": 2, "e": 5, "d": 4}]'>>> data = {'target_ip': u'192.168.16.120', 'kwargs': {u'server_ip': u'192.168.111.111'}}>>> json.dumps(data)'{"target_ip": "192.168.16.120", "kwargs": {"server_ip": "192.168.111.111"}}'>>>