JSONPath库：使用类似Xpath的语法解析JSON数据

简介

JSONPath是一种信息抽取类库，是从JSON文档中抽取指定信息的工具，提供多种语言实现版本，包括：Javascript, Python， PHP 和 Java。JsonPath 对于 JSON 来说，相当于 XPath 对于 XML。

官方文档：http://goessner.net/articles/JsonPath
安装方法：pip install jsonpath

JsonPath与Xpath语法对比

Json结构清晰，可读性高，复杂度低，非常容易匹配，下表中对应了XPath的用法。

XPath	JSONPath	描述
/	$	根节点
.	@	现行节点v
/	.or[]	取子节点
…	n/a	取父节点，Jsonpath未支持
//	…	就是不管位置，选择所有符合条件的条件
*	*	匹配所有元素节点
@	n/a	根据属性访问，Json不支持，因为Json是个Key-value递归结构，不需要。
[]	[]	迭代器标示（可以在里边做简单的迭代操作，如数组下标，根据内容选值等）
	[,]	支持迭代器中做多选。
[]	?()	支持过滤操作.
n/a	()	支持表达式计算
()	n/a	分组，JsonPath不支持

JSONPath表达式支持点号标记法和括号标记法。$.store.book[0].title等价于$['store']['book'][0]['title']

使用方法

JSONPath的API非常简单，最常用的就是jsonpath函数。

jsonpath函数的原型如下：jsonpath(obj, expr, result_type='VALUE', debug=0, use_eval=True)

参数如下：

obj：类型为字典，即JSON数据。必备参数。
expr：类型为字符串，即JSONPath表达式。必备参数。
result_type：类型为字符串，即返回值类型。可选参数。
- 默认值为'VALUE'，返回匹配的值。
- IPATH''，以列表形式返回匹配值的JSONPath路径索引。
- 其他值，返回匹配值的JSONPath表达式字符串。

返回值：类型为列表或False，无匹配值时返回值为False。

案例：JSONPath返回值类型

import jsonpath
from pprint import pprintjsonobj ={ "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}}
}# 返回值
all_prices = jsonpath.jsonpath(jsonobj,'$..price')
pprint(all_prices)
# 返回JSONPATH路径索引列表
all_prices = jsonpath.jsonpath(jsonobj,'$..price',result_type='IPATH')
pprint(all_prices)
# 返回JSONPATH表达式字符串
all_prices = jsonpath.jsonpath(jsonobj,'$..price',result_type='')
pprint(all_prices)

结果为：

[8.95, 12.99, 8.99, 22.99, 19.95]
[['store', 'book', '0', 'price'],['store', 'book', '1', 'price'],['store', 'book', '2', 'price'],['store', 'book', '3', 'price'],['store', 'bicycle', 'price']]
["$['store']['book'][0]['price']","$['store']['book'][1]['price']","$['store']['book'][2]['price']","$['store']['book'][3]['price']","$['store']['bicycle']['price']"]

案例：JSONPath综合应用

示例数据如下：

{ "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}}
}

XPath	JSONPath	含义
`/store/book/author`	`$.store.book[*].author`	商店中所有图书的作者
`//author`	`$..author`	所有作者
`/store/*`	`$.store.*`	商店中的所有商品
`/store//price`	`$.store..price`	商店中所有商品的价格
`//book[3]`	`$..book[2]`	第三本书的信息
`//book[last()]`	`$..book[(@.length-1)]` `$..book[-1:]`	最后一本书的信息
`//book[position()<3]`	`$..book[0,1]` `$..book[:2]`	前两本书的信息
`//book[isbn]`	`$..book[?(@.isbn)]`	筛选所有带isbn属性的图书
`//book[price<10]`	`$..book[?(@.price<10)]`	筛选价格低于10元的图书
`//*`	`$..*`	整个JSON

import jsonpath
from pprint import pprintjsonobj ={ "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}}
}
# 返回所有图书的价格
book_prices = jsonpath.jsonpath(jsonobj,'$.store.book[*].price')
pprint(book_prices)
# 返回所有商品的价格
all_prices = jsonpath.jsonpath(jsonobj,'$..price')
pprint(all_prices)
# 返回商店中所有商品的价格
store_prices = jsonpath.jsonpath(jsonobj,'$.store..price')
pprint(store_prices)
# 返回第三本书的信息
book3 = jsonpath.jsonpath(jsonobj,'$..book[2]')
pprint(book3)
# 返回第三本书的属性列表
book_attr = jsonpath.jsonpath(jsonobj,'$..book[2][*]')
pprint(book_attr)
# 返回第三本书的标题和作者
book_attr = jsonpath.jsonpath(jsonobj,'$..book[2][title,author]')
pprint(book_attr)
# 返回前两本书的信息
books12 = jsonpath.jsonpath(jsonobj,'$..book[:2]')
pprint(books12)
# 返回包含isbn属性的图书信息
isbns = jsonpath.jsonpath(jsonobj,'$..book[?(@.isbn)]')
pprint(isbns)
# 返回价格低于10元的图书
price10 = jsonpath.jsonpath(jsonobj,'$..book[?(@.price<10)]')
pprint(price10)