爬虫之数据提取jsonpath模块的使用场景和使用方法

爬虫之数据提取jsonpath模块的使用场景和使用方法

1. jsonpath模块的使用场景

如果有一个多层嵌套的复杂字典，想要根据key和下标来批量提取value，这是比较困难的。jsonpath模块就能解决这个痛点，接下来我们就来学习jsonpath模块

jsonpath可以按照key对python字典进行批量数据提取    【多层嵌套的复杂字典直接提取数据】

示例代码：

data = {'key1':  {'key2': {'key3': {'key4': {'key5': {'key6': 'python'}}}}}}
print(data)
print(data['key1']['key2']['key3']['key4']['key5']['key6'])

运行结果：

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2. jsonpath模块的使用方法

2.1 jsonpath模块的安装

jsonpath是第三方模块，需要额外安装

pip install jsonpath

2.2 jsonpath模块提取数据的方法         【jsonpath的结果为列表，获取数据需要索引】

from jsonpath import jsonpath
ret = jsonpath(a, 'jsonpath语法规则字符串')    #  此处的a就是对应的词典

2.3 jsonpath语法规则

示例代码：

from jsonpath import jsonpath


data = {'key1':  {'key2': {'key3': {'key4': {'key5': {'key6': 'python'}}}}}}
print(data)
#  jsonpath的结果为列表，获取数据需要索引
print(data['key1']['key2']['key3']['key4']['key5']['key6'])
print(jsonpath(data, '$.key1.key2.key3.key4.key5.key6'))
print(jsonpath(data, '$.key1.key2.key3.key4.key5.key6')[0])
print(jsonpath(data, '$..key6')[0])

运行效果：

2.4 jsonpath使用示例

from jsonpath import jsonpath


book_dict = {
  "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
    }
  }
}

print(jsonpath(book_dict, '$..author'))
print(jsonpath(book_dict, '$..prince'))
print(jsonpath(book_dict, '$..price'))
print(jsonpath(book_dict, '$..book..price'))
print(jsonpath(book_dict, '$..book'))
print(jsonpath(book_dict, '$..bicycle.color'))
print(jsonpath(book_dict, '$..color'))

【print(jsonpath(book_dict, '$..author'))   有一个输出一个，有多个则全部输出，若没有则报错】

运行效果：

3. jsonpath练习

我们以拉勾网城市JSON文件 http://www.lagou.com/lbs/getAllCitySearchLabels.json 为例，获取所有城市的名字的列表，并写入文件。

参考代码：

import requests
import json
import jsonpath

#  获取拉勾网城市json字符串
url = 'http://www.lagou.com/lbs/getAllCitySearchLabels.json'
headers = {
    "User-Agent": "Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)"
}
response = requests.get(url, headers=headers)
html_str = response.content.decode()
print(html_str)
#  把json格式字符串转换成python对象
jsonobj = json.loads(html_str)
print(jsonobj)
#  从根节点开始，获取所有key为name的值
citylist = jsonpath.jsonpath(jsonobj, '$..name')
print(citylist)

获取的json数据进行解析：

运行效果：