Python基礎-25 JSONPath用法

25 使用Python處理JSON資料

25.1 JSON簡介

25.1.1 什么是JSON

? ? JSON全稱為JavaScript Object Notation，一般翻譯為JS標記，是一種輕量級的資料交換格式，是基于ECMAScript的一個子集，采用完全獨立于編程語言的文本格式來存盤和表示資料，簡潔和清晰的層次結構使得JSON成為理想的資料交換語言，其主要特點有：易于閱讀、易于機器生成、有效提升網路速度等，

25.1.2 JSON的兩種結構

? ? JSON簡單來說，可以理解為JavaScript中的陣列和物件，通過這兩種結構，可以表示各種復雜的結構，

25.1.2.1 陣列

? ? 陣列在JavaScript是使用中括號[ ]來定義的，一般定義格式如下所示：

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

? ? 若要對陣列取值，則需要使用索引，元素的型別可以是數字、字串、陣列和物件等，

25.1.2.2 物件

? ? 物件在JavaScript是使用大括號{ }來定義的，一般定義格式如下所示：

let personInfo={
  name:"Surpass",
  age:28,
  location:"Shanghai"
}

? ? 物件一般是基于key和value，在JavaScript中，其取值方式也非常簡單variable.key即可，元素value的型別可以是數字、字串、陣列和物件等，

25.1.3 支持的資料格式

? ? JSON支持的主要資料格式如下所示：

• 陣列：使用中括號
• 物件：使用大括號
• 整型、浮點型、布爾型別和null
• 字串型別：必須使用雙引號，不能使用單引號

? ? 多個資料之間使用逗號做為分隔符，基與Python中的資料型別對應表如下所示：

25.2 Python對JSON的支持

25.2.1 Python 和 JSON 資料型別

? ? 在Python中主要使用json模塊來對JSON資料進行處理，在使用前，需要匯入json模塊，用法如下所示：

import json

? ? json模塊中主要包含以下四個操作函式，如下所示：

? ? 在json的處理過種中，Python中的原始型別與JSON型別會存在相互轉換，具體的轉換表如下所示：

• Python 轉換為 JSON

• JSON 轉換為 Python

25.2.2 json模塊常用方法

? ? 關于Python 內置的json模塊，可以查看之前我寫的文章：https://www.cnblogs.com/surpassme/p/13034972.html

25.3 使用JSONPath處理JSON資料

? ? 內置的json模塊，在處理簡單的JSON資料時，易用且非常非常方便，但在處理比較復雜且特別大的JSON資料，還是有一些費力，今天我們使用一個第三方的工具來處理JSON資料，叫JSONPath，

25.3.1 什么是JSONPath

? ? JSONPath是一種用于決議JSON資料的表達語言，經常用于決議和處理多層嵌套的JSON資料，其用法與決議XML資料的XPath運算式語言非常相似，

25.3.2 安裝

? ? 安裝方法如下所示：

# pip install -U jsonpath

25.3.3 JSONPath語法

? ? JSONPath語法與XPath非常相似，其對應參照表如下所示：

以上內容可查閱官方檔案：https://goessner.net/articles/JsonPath/

? ? 我們以下示例資料為例，來進行對比，如下所示：

{ "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
    }
  }
}

在XPath中，下標是1開始，而在JSONPath中是從0開始

JSONPath在線練習網址：http://jsonpath.com/

25.3.4 JSONPath用法

? ? 其基本用法形式如下所示：

jsonPath(obj, expr [, args])

? ? 基引數如下所示：

• obj (object|array):

? ? JSON資料物件

• expr (string):

? ? JSONPath運算式

• args (object|undefined):

? ? 改變輸出格式，比如是輸出是值還是路徑，

args.resultType可選的輸出格式為："VALUE"、"PATH"、"IPATH"

• 回傳型別為(array|false):

? ? 若回傳array，則代表成功匹配到資料，false則代表未匹配到資料，

25.3.5 在Python中的使用

from jsonpath import  jsonpath
import json

data = https://www.cnblogs.com/surpassme/p/{"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
            }
        }
}

#  獲取book節點中所有author
getAllBookAuthor=jsonpath(data,"$.store.book[*].author")
print(f"getAllBookAuthor is :{json.dumps(getAllBookAuthor,indent=4)}")
#  獲取book節點中所有author
getAllAuthor=jsonpath(data,"$..author")
print(f"getAllAuthor is {json.dumps(getAllAuthor,indent=4)}")
#  獲取store的元素，包含book和bicycle
getAllStoreElement=jsonpath(data,"$.store.*")
print(f"getAllStoreElement is {json.dumps(getAllStoreElement,indent=4)}")
# 獲取store中的所有price
getAllStorePriceA=jsonpath(data,"$[store]..price")
getAllStorePriceB=jsonpath(data,"$.store..price")
print(f"getAllStorePrictA is {getAllStorePriceA}\ngetAllStorePriceB is {getAllStorePriceB}")
# 獲取第三本書所有資訊
getThirdBookInfo=jsonpath(data,"$..book[2]")
print(f"getThirdBookInfo is {json.dumps(getThirdBookInfo,indent=4)}")
# 獲取最后一本書的資訊
getLastBookInfo=jsonpath(data,"$..book[-1:]")
print(f"getLastBookInfo is {json.dumps(getLastBookInfo,indent=4)}")
# 獲取前面的兩本書
getFirstAndSecondBookInfo=jsonpath(data,"$..book[:2]")
print(f"getFirstAndSecondBookInfo is {json.dumps(getFirstAndSecondBookInfo,indent=4)}")
#  根據isbn進行過濾
getWithFilterISBN=jsonpath(data,"$..book[?(@.isbn)]")
print(f"getWithFilterISBN is {json.dumps(getWithFilterISBN,indent=4)}")
# 根據price進行篩選
getWithFilterPrice=jsonpath(data,"$..book[?(@.price<10)]")
print(f"getWithFilterPrice is {json.dumps(getWithFilterPrice,indent=4)}")
# 所有元素
getAllElement=jsonpath(data,"$..*")
print(f"getAllElement is {json.dumps(getAllElement,indent=4)}")
# 未能匹配到元素時
noMatchElement=jsonpath(data,"$..surpass")
print(f"noMatchElement is {noMatchElement}")
# 調整輸出格式
controlleOutput=jsonpath(data,expr="$..author",result_type="PATH")
print(f"controlleOutput is {json.dumps(controlleOutput,indent=4)}")

? ? 最終輸出結果如下揚塵：

getAllBookAuthor is :[
    "Nigel Rees",
    "Evelyn Waugh",
    "Herman Melville",
    "J. R. R. Tolkien"
]
getAllAuthor is [
    "Nigel Rees",
    "Evelyn Waugh",
    "Herman Melville",
    "J. R. R. Tolkien"
]
getAllStoreElement is [
    [
        {
            "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
        }
    ],
    {
        "color": "red",
        "price": 19.95
    }
]
getAllStorePrictA is [8.95, 12.99, 8.99, 22.99, 19.95]
getAllStorePriceB is [8.95, 12.99, 8.99, 22.99, 19.95]
getThirdBookInfo is [
    {
        "category": "fiction",
        "author": "Herman Melville",
        "title": "Moby Dick",
        "isbn": "0-553-21311-3",
        "price": 8.99
    }
]
getLastBookInfo is [
    {
        "category": "fiction",
        "author": "J. R. R. Tolkien",
        "title": "The Lord of the Rings",
        "isbn": "0-395-19395-8",
        "price": 22.99
    }
]
getFirstAndSecondBookInfo is [
    {
        "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
    }
]
getWithFilterISBN is [
    {
        "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
    }
]
getWithFilterPrice is [
    {
        "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
    }
]
getAllElement is [
    {
        "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
        }
    },
    [
        {
            "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
        }
    ],
    {
        "color": "red",
        "price": 19.95
    },
    {
        "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
    },
    "reference",
    "Nigel Rees",
    "Sayings of the Century",
    8.95,
    "fiction",
    "Evelyn Waugh",
    "Sword of Honour",
    12.99,
    "fiction",
    "Herman Melville",
    "Moby Dick",
    "0-553-21311-3",
    8.99,
    "fiction",
    "J. R. R. Tolkien",
    "The Lord of the Rings",
    "0-395-19395-8",
    22.99,
    "red",
    19.95
]
noMatchElement is False
controlleOutput is [
    "$['store']['book'][0]['author']",
    "$['store']['book'][1]['author']",
    "$['store']['book'][2]['author']",
    "$['store']['book'][3]['author']"
]

原文地址：https://www.jianshu.com/p/a69a9cf293bd

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作者： Surpassme

來源： http://www.jianshu.com/u/28161b7c9995/

http://www.cnblogs.com/surpassme/

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