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jsonpath:使用Python处理JSON数据_python json数组

作者：神奇cpp | 2024-08-04 09:18:00

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python json数组

使用Python处理JSON数据

25.1 JSON简介

25.1.1 什么是JSON

    JSON全称为JavaScript Object Notation，一般翻译为JS标记，是一种轻量级的数据交换格式。是基于ECMAScript的一个子集，采用完全独立于编程语言的文本格式来存储和表示数据。简洁和清晰的层次结构使得JSON成为理想的数据交换语言，其主要特点有：易于阅读、易于机器生成、有效提升网络速度等。

25.1.2 JSON的两种结构

    JSON简单来说，可以理解为JavaScript中的数组和对象，通过这两种结构，可以表示各种复杂的结构。

25.1.2.1 数组

    数组在JavaScript是使用中括号[ ]来定义的，一般定义格式如下所示：

let array=["Surpass","28","Shanghai"];

    若要对数组取值，则需要使用索引。元素的类型可以是数字、字符串、数组和对象等。

25.1.2.2 对象

    对象在JavaScript是使用大括号{ }来定义的，一般定义格式如下所示：

  1. let personInfo={
  2.   name:"Surpass",
  3.   age:28,
  4.   location:"Shanghai"
  5. }

    对象一般是基于key和value，在JavaScript中，其取值方式也非常简单variable.key即可。元素value的类型可以是数字、字符串、数组和对象等。

25.1.3 支持的数据格式

    JSON支持的主要数据格式如下所示：

  • 数组：使用中括号
  • 对象：使用大括号
  • 整型、浮点型、布尔类型和null
  • 字符串类型：必须使用双引号，不能使用单引号

    多个数据之间使用逗号做为分隔符，基与Python中的数据类型对应表如下所示：

JSONPython
Objectdict
arraylist
stringstr
number(int)int
number(real)float
trueTrue
falseFalse
nullNone

25.2 Python对JSON的支持

25.2.1 Python 和 JSON 数据类型

    在Python中主要使用json模块来对JSON数据进行处理。在使用前，需要导入json模块，用法如下所示：

import json

    json模块中主要包含以下四个操作函数，如下所示：

    在json的处理过种中，Python中的原始类型与JSON类型会存在相互转换，具体的转换表如下所示：

  • Python 转换为 JSON
PythonJSON
dictObject
listarray
tuplearray
strstring
intnumber
floatnumber
Truetrue
Falsefalse
Nonenull
  • JSON 转换为 Python
JSONPython
Objectdict
arraylist
stringstr
number(int)int
number(real)float
trueTrue
falseFalse
nullNone
25.2.2 json模块常用方法

    关于Python 内置的json模块，可以查看之前我写的文章：https://www.cnblogs.com/surpassme/p/13034972.html

25.3 使用JSONPath处理JSON数据

    内置的json模块，在处理简单的JSON数据时，易用且非常非常方便，但在处理比较复杂且特别大的JSON数据，还是有一些费力，今天我们使用一个第三方的工具来处理JSON数据，叫JSONPath。

25.3.1 什么是JSONPath

    JSONPath是一种用于解析JSON数据的表达语言。经常用于解析和处理多层嵌套的JSON数据，其用法与解析XML数据的XPath表达式语言非常相似。

25.3.2 安装

    安装方法如下所示：

# pip install -U jsonpath
25.3.3 JSONPath语法

    JSONPath语法与XPath非常相似，其对应参照表如下所示：

XPathJSONPath描述
/$根节点/元素
.@当前节点/元素
/. or []子元素
..n/a父元素
//..递归向下搜索子元素
**通配符，表示所有元素
@n/a访问属性，JSON结构的数据没有这种属性
[][]子元素操作符(可以在里面做简单的迭代操作，如数据索引，根据内容选值等)
|[,]支持迭代器中做多选
n/a[start :end :step]数组分割操作
[]?()筛选表达式
n/a()支持表达式计算
()n/a分组，JSONPath不支持

以上内容可查阅官方文档：JSONPath - XPath for JSON

    我们以下示例数据为例，来进行对比，如下所示：

  1. { "store": 
  2.   {
  3.     "book": [ 
  4.       { "category": "reference",
  5.         "author": "Nigel Rees",
  6.         "title": "Sayings of the Century",
  7.         "price": 8.95
  8.       },
  9.       { "category": "fiction",
  10.         "author": "Evelyn Waugh",
  11.         "title": "Sword of Honour",
  12.         "price": 12.99
  13.       },
  14.       { "category": "fiction",
  15.         "author": "Herman Melville",
  16.         "title": "Moby Dick",
  17.         "isbn": "0-553-21311-3",
  18.         "price": 8.99
  19.       },
  20.       { "category": "fiction",
  21.         "author": "J. R. R. Tolkien",
  22.         "title": "The Lord of the Rings",
  23.         "isbn": "0-395-19395-8",
  24.         "price": 22.99
  25.       }
  26.     ],
  27.     "bicycle": {
  28.       "color": "red",
  29.       "price": 19.95
  30.     }
  31.   }
  32. }
XPathJSONPath结果
/store/book/author$.store.book[*].author获取book节点中所有author
//author$..author获取所有author
/store/*$.store.*获取store的元素，包含book和bicycle
/store//price$.store..price获取store中的所有price
//book[3]$..book[2]获取第三本书所有信息
//book[last()]..����[(@.�����ℎ−1)]..book[-1:]获取最后一本书的信息
//book[position()❤️]..����[0,1]..book[:2]获取前面的两本书
//book[isbn]$..book[?(@.isbn)]根据isbn进行过滤
//book[price<10]$..book[?(@.price<10)]根据price进行筛选
//*$..*所有元素

在XPath中，下标是1开始，而在JSONPath中是从0开始

JSONPath在线练习网址：JSONPath Online Evaluator

25.3.4 JSONPath用法

    其基本用法形式如下所示：

jsonPath(obj, expr [, args])

    基参数如下所示：

  • obj (object|array):

    JSON数据对象

  • expr (string):

    JSONPath表达式

  • args (object|undefined):

    改变输出格式，比如是输出是值还是路径，

args.resultType可选的输出格式为："VALUE"、"PATH"、"IPATH"

  • 返回类型为(array|false):

    若返回array，则代表成功匹配到数据，false则代表未匹配到数据。

25.3.5 在Python中的使用
  1. from jsonpath import  jsonpath
  2. import json
  3.  
  4. data = {
  5.     "store":
  6.         {
  7.             "book": [
  8.                 {
  9.                     "category": "reference",
  10.                     "author": "Nigel Rees",
  11.                     "title": "Sayings of the Century",
  12.                     "price": 8.95
  13.                 },
  14.                 {
  15.                     "category": "fiction",
  16.                     "author": "Evelyn Waugh",
  17.                     "title": "Sword of Honour",
  18.                     "price": 12.99
  19.                 },
  20.                 {
  21.                     "category": "fiction",
  22.                     "author": "Herman Melville",
  23.                     "title": "Moby Dick",
  24.                     "isbn": "0-553-21311-3",
  25.                     "price": 8.99
  26.                 },
  27.                 {
  28.                     "category": "fiction",
  29.                     "author": "J. R. R. Tolkien",
  30.                     "title": "The Lord of the Rings",
  31.                     "isbn": "0-395-19395-8",
  32.                     "price": 22.99
  33.                 }
  34.             ],
  35.             "bicycle": {
  36.                 "color": "red",
  37.                 "price": 19.95
  38.             }
  39.         }
  40. }
  41.  
  42. #  获取book节点中所有author
  43. getAllBookAuthor=jsonpath(data,"$.store.book[*].author")
  44. print(f"getAllBookAuthor is :{json.dumps(getAllBookAuthor,indent=4)}")
  45. #  获取book节点中所有author
  46. getAllAuthor=jsonpath(data,"$..author")
  47. print(f"getAllAuthor is {json.dumps(getAllAuthor,indent=4)}")
  48. #  获取store的元素，包含book和bicycle
  49. getAllStoreElement=jsonpath(data,"$.store.*")
  50. print(f"getAllStoreElement is {json.dumps(getAllStoreElement,indent=4)}")
  51. # 获取store中的所有price
  52. getAllStorePriceA=jsonpath(data,"$[store]..price")
  53. getAllStorePriceB=jsonpath(data,"$.store..price")
  54. print(f"getAllStorePrictA is {getAllStorePriceA}\ngetAllStorePriceB is {getAllStorePriceB}")
  55. # 获取第三本书所有信息
  56. getThirdBookInfo=jsonpath(data,"$..book[2]")
  57. print(f"getThirdBookInfo is {json.dumps(getThirdBookInfo,indent=4)}")
  58. # 获取最后一本书的信息
  59. getLastBookInfo=jsonpath(data,"$..book[-1:]")
  60. print(f"getLastBookInfo is {json.dumps(getLastBookInfo,indent=4)}")
  61. # 获取前面的两本书
  62. getFirstAndSecondBookInfo=jsonpath(data,"$..book[:2]")
  63. print(f"getFirstAndSecondBookInfo is {json.dumps(getFirstAndSecondBookInfo,indent=4)}")
  64. #  根据isbn进行过滤
  65. getWithFilterISBN=jsonpath(data,"$..book[?(@.isbn)]")
  66. print(f"getWithFilterISBN is {json.dumps(getWithFilterISBN,indent=4)}")
  67. # 根据price进行筛选
  68. getWithFilterPrice=jsonpath(data,"$..book[?(@.price<10)]")
  69. print(f"getWithFilterPrice is {json.dumps(getWithFilterPrice,indent=4)}")
  70. # 所有元素
  71. getAllElement=jsonpath(data,"$..*")
  72. print(f"getAllElement is {json.dumps(getAllElement,indent=4)}")
  73. # 未能匹配到元素时
  74. noMatchElement=jsonpath(data,"$..surpass")
  75. print(f"noMatchElement is {noMatchElement}")
  76. # 调整输出格式
  77. controlleOutput=jsonpath(data,expr="$..author",result_type="PATH")
  78. print(f"controlleOutput is {json.dumps(controlleOutput,indent=4)}")

    最终输出结果如下扬尘：

  1. getAllBookAuthor is :[
  2.     "Nigel Rees",
  3.     "Evelyn Waugh",
  4.     "Herman Melville",
  5.     "J. R. R. Tolkien"
  6. ]
  7. getAllAuthor is [
  8.     "Nigel Rees",
  9.     "Evelyn Waugh",
  10.     "Herman Melville",
  11.     "J. R. R. Tolkien"
  12. ]
  13. getAllStoreElement is [
  14.     [
  15.         {
  16.             "category": "reference",
  17.             "author": "Nigel Rees",
  18.             "title": "Sayings of the Century",
  19.             "price": 8.95
  20.         },
  21.         {
  22.             "category": "fiction",
  23.             "author": "Evelyn Waugh",
  24.             "title": "Sword of Honour",
  25.             "price": 12.99
  26.         },
  27.         {
  28.             "category": "fiction",
  29.             "author": "Herman Melville",
  30.             "title": "Moby Dick",
  31.             "isbn": "0-553-21311-3",
  32.             "price": 8.99
  33.         },
  34.         {
  35.             "category": "fiction",
  36.             "author": "J. R. R. Tolkien",
  37.             "title": "The Lord of the Rings",
  38.             "isbn": "0-395-19395-8",
  39.             "price": 22.99
  40.         }
  41.     ],
  42.     {
  43.         "color": "red",
  44.         "price": 19.95
  45.     }
  46. ]
  47. getAllStorePrictA is [8.95, 12.99, 8.99, 22.99, 19.95]
  48. getAllStorePriceB is [8.95, 12.99, 8.99, 22.99, 19.95]
  49. getThirdBookInfo is [
  50.     {
  51.         "category": "fiction",
  52.         "author": "Herman Melville",
  53.         "title": "Moby Dick",
  54.         "isbn": "0-553-21311-3",
  55.         "price": 8.99
  56.     }
  57. ]
  58. getLastBookInfo is [
  59.     {
  60.         "category": "fiction",
  61.         "author": "J. R. R. Tolkien",
  62.         "title": "The Lord of the Rings",
  63.         "isbn": "0-395-19395-8",
  64.         "price": 22.99
  65.     }
  66. ]
  67. getFirstAndSecondBookInfo is [
  68.     {
  69.         "category": "reference",
  70.         "author": "Nigel Rees",
  71.         "title": "Sayings of the Century",
  72.         "price": 8.95
  73.     },
  74.     {
  75.         "category": "fiction",
  76.         "author": "Evelyn Waugh",
  77.         "title": "Sword of Honour",
  78.         "price": 12.99
  79.     }
  80. ]
  81. getWithFilterISBN is [
  82.     {
  83.         "category": "fiction",
  84.         "author": "Herman Melville",
  85.         "title": "Moby Dick",
  86.         "isbn": "0-553-21311-3",
  87.         "price": 8.99
  88.     },
  89.     {
  90.         "category": "fiction",
  91.         "author": "J. R. R. Tolkien",
  92.         "title": "The Lord of the Rings",
  93.         "isbn": "0-395-19395-8",
  94.         "price": 22.99
  95.     }
  96. ]
  97. getWithFilterPrice is [
  98.     {
  99.         "category": "reference",
  100.         "author": "Nigel Rees",
  101.         "title": "Sayings of the Century",
  102.         "price": 8.95
  103.     },
  104.     {
  105.         "category": "fiction",
  106.         "author": "Herman Melville",
  107.         "title": "Moby Dick",
  108.         "isbn": "0-553-21311-3",
  109.         "price": 8.99
  110.     }
  111. ]
  112. getAllElement is [
  113.     {
  114.         "book": [
  115.             {
  116.                 "category": "reference",
  117.                 "author": "Nigel Rees",
  118.                 "title": "Sayings of the Century",
  119.                 "price": 8.95
  120.             },
  121.             {
  122.                 "category": "fiction",
  123.                 "author": "Evelyn Waugh",
  124.                 "title": "Sword of Honour",
  125.                 "price": 12.99
  126.             },
  127.             {
  128.                 "category": "fiction",
  129.                 "author": "Herman Melville",
  130.                 "title": "Moby Dick",
  131.                 "isbn": "0-553-21311-3",
  132.                 "price": 8.99
  133.             },
  134.             {
  135.                 "category": "fiction",
  136.                 "author": "J. R. R. Tolkien",
  137.                 "title": "The Lord of the Rings",
  138.                 "isbn": "0-395-19395-8",
  139.                 "price": 22.99
  140.             }
  141.         ],
  142.         "bicycle": {
  143.             "color": "red",
  144.             "price": 19.95
  145.         }
  146.     },
  147.     [
  148.         {
  149.             "category": "reference",
  150.             "author": "Nigel Rees",
  151.             "title": "Sayings of the Century",
  152.             "price": 8.95
  153.         },
  154.         {
  155.             "category": "fiction",
  156.             "author": "Evelyn Waugh",
  157.             "title": "Sword of Honour",
  158.             "price": 12.99
  159.         },
  160.         {
  161.             "category": "fiction",
  162.             "author": "Herman Melville",
  163.             "title": "Moby Dick",
  164.             "isbn": "0-553-21311-3",
  165.             "price": 8.99
  166.         },
  167.         {
  168.             "category": "fiction",
  169.             "author": "J. R. R. Tolkien",
  170.             "title": "The Lord of the Rings",
  171.             "isbn": "0-395-19395-8",
  172.             "price": 22.99
  173.         }
  174.     ],
  175.     {
  176.         "color": "red",
  177.         "price": 19.95
  178.     },
  179.     {
  180.         "category": "reference",
  181.         "author": "Nigel Rees",
  182.         "title": "Sayings of the Century",
  183.         "price": 8.95
  184.     },
  185.     {
  186.         "category": "fiction",
  187.         "author": "Evelyn Waugh",
  188.         "title": "Sword of Honour",
  189.         "price": 12.99
  190.     },
  191.     {
  192.         "category": "fiction",
  193.         "author": "Herman Melville",
  194.         "title": "Moby Dick",
  195.         "isbn": "0-553-21311-3",
  196.         "price": 8.99
  197.     },
  198.     {
  199.         "category": "fiction",
  200.         "author": "J. R. R. Tolkien",
  201.         "title": "The Lord of the Rings",
  202.         "isbn": "0-395-19395-8",
  203.         "price": 22.99
  204.     },
  205.     "reference",
  206.     "Nigel Rees",
  207.     "Sayings of the Century",
  208.     8.95,
  209.     "fiction",
  210.     "Evelyn Waugh",
  211.     "Sword of Honour",
  212.     12.99,
  213.     "fiction",
  214.     "Herman Melville",
  215.     "Moby Dick",
  216.     "0-553-21311-3",
  217.     8.99,
  218.     "fiction",
  219.     "J. R. R. Tolkien",
  220.     "The Lord of the Rings",
  221.     "0-395-19395-8",
  222.     22.99,
  223.     "red",
  224.     19.95
  225. ]
  226. noMatchElement is False
  227. controlleOutput is [
  228.     "$['store']['book'][0]['author']",
  229.     "$['store']['book'][1]['author']",
  230.     "$['store']['book'][2]['author']",
  231.     "$['store']['book'][3]['author']"
  232. ]
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