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.

參考：http://json.org/

JSON 語法規則

JSON 語法是 JavaScript 對象表示法語法的子集。

JSON 名稱/值對

JSON 數據的書寫格式是：名稱/值對。

名稱/值對包括字段名稱（在雙引號中），后面寫一個冒號，然后是值：

"firstName" : "John"
這很容易理解，等價于這條 JavaScript 語句：
firstName = "John"
JSON 值
JSON 值可以是：
數字（整數或浮點數）字符串（在雙引號中）邏輯值（true 或 false）數組（在方括號中）對象（在花括號中）null
JSON 對象
JSON 對象在花括號中書寫：
對象可以包含多個名稱/值對：
{ "firstName":"John" , "lastName":"Doe" }
這一點也容易理解，與這條 JavaScript 語句等價：
firstName = "John"lastName = "Doe"
JSON 數組
JSON 數組在方括號中書寫：
數組可包含多個對象：
{"employees": [{ "firstName":"John" , "lastName":"Doe" },{ "firstName":"Anna" , "lastName":"Smith" },{ "firstName":"Peter" , "lastName":"Jones" }]}
在上面的例子中，對象 "employees" 是包含三個對象的數組。每個對象代表一條關于某人（有姓和名）的記錄。
JSON 文件
JSON 文件的文件類型是 ".json"JSON 文本的 MIME 類型是 "application/json"
參考：http://www.runoob.com/json/json-tutorial.html
2 Python JSON
兩個主要的函數是 json.dumps() 和 json.loads()
3 實例
3.1 json.dumps
在做HTTP API開發時，通過REST Client下發POST請求，請求的Payload為：
{    "target_ip": "192.168.16.120",    "kwargs": {        "server_ip": "192.168.111.117"    }}HTTP請求的自定義Header是：
Accept	application/json	  Content-Type	application/json
當程序收到Payload后，打印結果與入庫后的結果都是Unicode串：
{'target_ip': u'192.168.16.120', 'kwargs': {u'server_ip': u'192.168.111.111'}}
但是要在庫中存非Unicode串，怎么做？
用json.dumps來轉換字符串，轉換后輸出：
{"target_ip": "192.168.16.120", "kwargs": {"server_ip": "192.168.111.111"}用python執行：
>>> 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"}}'>>>