Python之JsonPath的使用

JsonPath的来源

正如XPath之于XML文档一样，JsonPath为Json文档提供了解析能力，通过使用JsonPath，你可以方便的查找节点、获取想要的数据，JsonPath是Json版的XPath。

JsonPath语法

JSONPATH	描述
$	根对象或元素
@	当前对象或元素
. or []	子元素操作符
..	递归匹配所有子元素
*	通配符，匹配所有对象或元素
[]	下标运算法，JSONPATH索引从0开始
[,]	连接运算符，将多个结果拼成数组返回，JSONPATH允许使用别名
[start:end:step]	数组切片运算符
?()	过滤器（脚本）表达式
()	脚本表达式

注意：JsonPath中字符串使用单引号表示，例如：$.store.book[?(@.category=='reference')]中的'reference'

python中jsonpath模块的运用

首先安装jsonpath：pip install jsonpath

import jsonpath

author = jsonpath.jsonpath(data, 'jsonpath表达式')

注意：jsonpath表达式返回的都是列表。

操作实例（操作对象为json，非json需先转化）：

{ "store": {
    "book": [
      { "category": "reference",
        "author": "Nigel Rees",
        "title": "Sayings of the Century",
        "price": 8.95
      },
      { "category": "fiction",
        "author": "Evelyn Waugh",
        "title": "Sword of Honour",
        "price": 12.99
      },
      { "category": "fiction",
        "author": "Herman Melville",
        "title": "Moby Dick",
        "isbn": "0-553-21311-3",
        "price": 8.99
      },
      { "category": "fiction",
        "author": "J. R. R. Tolkien",
        "title": "The Lord of the Rings",
        "isbn": "0-395-19395-8",
        "price": 22.99
      }
    ],
    "bicycle": {
      "color": "red",
      "price": 19.95
    }
  },
  "expensive": 10
}

点击此链接可在线验证jsonpath的正确性

获取某个字段的所有值：
例：获取json中store下book下的所有author值

$.store.book..author
or 
$.store.book[*].author

运行结果：

[  "Nigel Rees",  "Evelyn Waugh",  "Herman Melville",  "J. R. R. Tolkien"]

切片获取某个数组的部分值：
例：获取json中book数组的第二三本书

$..book[1:3]

运行结果：

[  {    "category": "fiction",    "author": "Evelyn Waugh",    "title": "Sword of Honour",    "price": 12.99  },  {    "category": "fiction",    "author": "Herman Melville",    "title": "Moby Dick",    "isbn": "0-553-21311-3",    "price": 8.99  }]

获取某个数组包含某字段的值：
例：获取json中book数组中包含isbn的所有值

$..book[?(@.isbn)]

运行结果：

[  {    "category": "fiction",    "author": "Herman Melville",    "title": "Moby Dick",    "isbn": "0-553-21311-3",    "price": 8.99  },  {    "category": "fiction",    "author": "J. R. R. Tolkien",    "title": "The Lord of the Rings",    "isbn": "0-395-19395-8",    "price": 22.99  }]

获取某个数组满足某个判断条件的值：
例：获取json中book数组中price小于等于10的值

$..book[?(@.price <= 10)]

运行结果：

[  {    "category": "reference",    "author": "Nigel Rees",    "title": "Sayings of the Century",    "price": 8.95  },  {    "category": "fiction",    "author": "Herman Melville",    "title": "Moby Dick",    "isbn": "0-553-21311-3",    "price": 8.99  }]

获取数组中A字段满足某一条件的同级B字段值
例：获取json中book数组中category为fiction书本的price

$..book[?(@.category == 'fiction')].price

运行结果：

[  12.99,  8.99,  22.99]