Pandas处理 JSON 数据

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Pandas 可以很方便的处理 JSON 数据,本文以 sites.json 为例,内容如下:

实例 [ { "id": "A001", "name": "菜鸟教程", "url": "www.runoob.com", "likes": 61 }, { "id": "A002", "name": "Google", "url": "www.google.com", "likes": 124 }, { "id": "A003", "name": "淘宝", "url": "www.taobao.com", "likes": 45 } ] 实例 import pandas as pd

df = pd.read_json('sites.json')

print(df.to_string()) to_string() 用于返回 DataFrame 类型的数据,我们也可以直接处理 JSON 字符串。

实例 import pandas as pd

data =[ { "id": "A001", "name": "菜鸟教程", "url": "www.runoob.com", "likes": 61 }, { "id": "A002", "name": "Google", "url": "www.google.com", "likes": 124 }, { "id": "A003", "name": "淘宝", "url": "www.taobao.com", "likes": 45 } ] df = pd.DataFrame(data)

print(df) 以上实例输出结果为:

 id    name             url  likes

0 A001 菜鸟教程 www.runoob.com 61 1 A002 Google www.google.com 124 2 A003 淘宝 www.taobao.com 45 JSON 对象与 Python 字典具有相同的格式,所以我们可以直接将 Python 字典转化为 DataFrame 数据:

实例 import pandas as pd

字典格式的 JSON

s = { "col1":{"row1":1,"row2":2,"row3":3}, "col2":{"row1":"x","row2":"y","row3":"z"} }

读取 JSON 转为 DataFrame

df = pd.DataFrame(s) print(df) 以上实例输出结果为:

  col1 col2

row1 1 x row2 2 y row3 3 z 从 URL 中读取 JSON 数据:

实例 import pandas as pd

URL = 'static.runoob.com/download/si…' df = pd.read_json(URL) print(df) 以上实例输出结果为:

 id    name             url  likes

0 A001 菜鸟教程 www.runoob.com 61 1 A002 Google www.google.com 124 2 A003 淘宝 www.taobao.com 45 内嵌的 JSON 数据 假设有一组内嵌的 JSON 数据文件 nested_list.json : nested_list.json 文件内容 { "school_name": "ABC primary school", "class": "Year 1", "students": [ { "id": "A001", "name": "Tom", "math": 60, "physics": 66, "chemistry": 61 }, { "id": "A002", "name": "James", "math": 89, "physics": 76, "chemistry": 51 }, { "id": "A003", "name": "Jenny", "math": 79, "physics": 90, "chemistry": 78 }] } 使用以下代码格式化完整内容:

实例 import pandas as pd

df = pd.read_json('nested_list.json')

print(df) 以上实例输出结果为:

      school_name   class                                           students

0 ABC primary school Year 1 {'id': 'A001', 'name': 'Tom', 'math': 60, 'phy... 1 ABC primary school Year 1 {'id': 'A002', 'name': 'James', 'math': 89, 'p... 2 ABC primary school Year 1 {'id': 'A003', 'name': 'Jenny', 'math': 79, 'p... 这时我们就需要使用到 json_normalize() 方法将内嵌的数据完整的解析出来:

实例 import pandas as pd import json

使用 Python JSON 模块载入数据

with open('nested_list.json','r') as f: data = json.loads(f.read())

展平数据

df_nested_list = pd.json_normalize(data, record_path =['students']) print(df_nested_list) 以上实例输出结果为:

 id   name  math  physics  chemistry

0 A001 Tom 60 66 61 1 A002 James 89 76 51 2 A003 Jenny 79 90 78 data = json.loads(f.read()) 使用 Python JSON 模块载入数据。

json_normalize() 使用了参数 record_path 并设置为 ['students'] 用于展开内嵌的 JSON 数据 students。

显示结果还没有包含 school_name 和 class 元素,如果需要展示出来可以使用 meta 参数来显示这些元数据:

实例 import pandas as pd import json

使用 Python JSON 模块载入数据

with open('nested_list.json','r') as f: data = json.loads(f.read())

展平数据

df_nested_list = pd.json_normalize( data, record_path =['students'], meta=['school_name', 'class'] ) print(df_nested_list) 以上实例输出结果为:

 id   name  math  physics  chemistry         school_name   class

0 A001 Tom 60 66 61 ABC primary school Year 1 1 A002 James 89 76 51 ABC primary school Year 1 2 A003 Jenny 79 90 78 ABC primary school Year 1 接下来,让我们尝试读取更复杂的 JSON 数据,该数据嵌套了列表和字典,数据文件 nested_mix.json 如下:

nested_mix.json 文件内容 { "school_name": "local primary school", "class": "Year 1", "info": { "president": "John Kasich", "address": "ABC road, London, UK", "contacts": { "email": "admin@e.com", "tel": "123456789" } }, "students": [ { "id": "A001", "name": "Tom", "math": 60, "physics": 66, "chemistry": 61 }, { "id": "A002", "name": "James", "math": 89, "physics": 76, "chemistry": 51 }, { "id": "A003", "name": "Jenny", "math": 79, "physics": 90, "chemistry": 78 }] } nested_mix.json 文件转换为 DataFrame:

实例 import pandas as pd import json

使用 Python JSON 模块载入数据

with open('nested_mix.json','r') as f: data = json.loads(f.read())

df = pd.json_normalize( data, record_path =['students'], meta=[ 'class', ['info', 'president'], ['info', 'contacts', 'tel'] ] )

print(df) 以上实例输出结果为:

 id   name  math  physics  chemistry   class info.president info.contacts.tel

0 A001 Tom 60 66 61 Year 1 John Kasich 123456789 1 A002 James 89 76 51 Year 1 John Kasich 123456789 2 A003 Jenny 79 90 78 Year 1 John Kasich 123456789 读取内嵌数据中的一组数据 以下是实例文件 nested_deep.json,我们只读取内嵌中的 math 字段:

nested_deep.json 文件内容 { "school_name": "local primary school", "class": "Year 1", "students": [ { "id": "A001", "name": "Tom", "grade": { "math": 60, "physics": 66, "chemistry": 61 }

},
{
    "id": "A002",
    "name": "James",
    "grade": {
        "math": 89,
        "physics": 76,
        "chemistry": 51
    }
   
},
{
    "id": "A003",
    "name": "Jenny",
    "grade": {
        "math": 79,
        "physics": 90,
        "chemistry": 78
    }
}]

} 这里我们需要使用到 glom 模块来处理数据套嵌,glom 模块允许我们使用 . 来访问内嵌对象的属性。

第一次使用我们需要安装 glom:

pip3 install glom 实例 import pandas as pd from glom import glom

df = pd.read_json('nested_deep.json')

data = df['students'].apply(lambda row: glom(row, 'grade.math')) print(data) 以上实例输出结果为:

0 60 1 89 2 79 Name: students, dtype: int64