如何将JSON转换为CSV？

Question

我有一个JSON文件要转换成CSV文件。我怎么能用Python做到这一点？

我试过：

import json
import csv

f = open('data.json')
data = json.load(f)
f.close()

f = open('data.csv')
csv_file = csv.writer(f)
for item in data:
    csv_file.writerow(item)

f.close()

然而，它没有起作用。我正在使用Django，收到的错误是：

file' object has no attribute 'writerow'

然后我尝试了以下方法：

import json
import csv

f = open('data.json')
data = json.load(f)
f.close()

f = open('data.csv')
csv_file = csv.writer(f)
for item in data:
    f.writerow(item)  # ← changed

f.close()

然后我得到错误：

sequence expected

示例json文件：

[{
        "pk": 22,
        "model": "auth.permission",
        "fields": {
            "codename": "add_logentry",
            "name": "Can add log entry",
            "content_type": 8
        }
    }, {
        "pk": 23,
        "model": "auth.permission",
        "fields": {
            "codename": "change_logentry",
            "name": "Can change log entry",
            "content_type": 8
        }
    }, {
        "pk": 24,
        "model": "auth.permission",
        "fields": {
            "codename": "delete_logentry",
            "name": "Can delete log entry",
            "content_type": 8
        }
    }, {
        "pk": 4,
        "model": "auth.permission",
        "fields": {
            "codename": "add_group",
            "name": "Can add group",
            "content_type": 2
        }
    }, {
        "pk": 10,
        "model": "auth.permission",
        "fields": {
            "codename": "add_message",
            "name": "Can add message",
            "content_type": 4
        }
    }
]

Answer 1

首先，JSON有嵌套对象，因此通常不能直接转换为CSV。你需要把它改成这样：

{
    "pk": 22,
    "model": "auth.permission",
    "codename": "add_logentry",
    "content_type": 8,
    "name": "Can add log entry"
},
......]

下面是我从中生成CSV的代码：

import csv
import json

x = """[
    {
        "pk": 22,
        "model": "auth.permission",
        "fields": {
            "codename": "add_logentry",
            "name": "Can add log entry",
            "content_type": 8
        }
    },
    {
        "pk": 23,
        "model": "auth.permission",
        "fields": {
            "codename": "change_logentry",
            "name": "Can change log entry",
            "content_type": 8
        }
    },
    {
        "pk": 24,
        "model": "auth.permission",
        "fields": {
            "codename": "delete_logentry",
            "name": "Can delete log entry",
            "content_type": 8
        }
    }
]"""

x = json.loads(x)

f = csv.writer(open("test.csv", "wb+"))

# Write CSV Header, If you dont need that, remove this line
f.writerow(["pk", "model", "codename", "name", "content_type"])

for x in x:
    f.writerow([x["pk"],
                x["model"],
                x["fields"]["codename"],
                x["fields"]["name"],
                x["fields"]["content_type"]])

输出为：

pk,model,codename,name,content_type
22,auth.permission,add_logentry,Can add log entry,8
23,auth.permission,change_logentry,Can change log entry,8
24,auth.permission,delete_logentry,Can delete log entry,8

Answer 2

我假设您的JSON文件将解码成一个字典列表。首先，我们需要一个函数来压平JSON对象：

def flattenjson( b, delim ):
    val = {}
    for i in b.keys():
        if isinstance( b[i], dict ):
            get = flattenjson( b[i], delim )
            for j in get.keys():
                val[ i + delim + j ] = get[j]
        else:
            val[i] = b[i]

    return val

在JSON对象上运行此代码段的结果：

flattenjson( {
    "pk": 22, 
    "model": "auth.permission", 
    "fields": {
      "codename": "add_message", 
      "name": "Can add message", 
      "content_type": 8
    }
  }, "__" )

是

{
    "pk": 22, 
    "model": "auth.permission', 
    "fields__codename": "add_message", 
    "fields__name": "Can add message", 
    "fields__content_type": 8
}

将此函数应用于JSON对象的输入数组中的每个dict之后：

input = map( lambda x: flattenjson( x, "__" ), input )

找到相关的列名：

columns = [ x for row in input for x in row.keys() ]
columns = list( set( columns ) )

通过csv模块运行这个并不难：

with open( fname, 'wb' ) as out_file:
    csv_w = csv.writer( out_file )
    csv_w.writerow( columns )

    for i_r in input:
        csv_w.writerow( map( lambda x: i_r.get( x, "" ), columns ) )

我希望这有帮助！

Answer 3

使用pandaslibrary，这就像使用两个命令一样简单！

pandas.read_json()

将JSON字符串转换为pandas对象（序列或数据帧）。然后，假设结果存储为df：

df.to_csv()

它可以返回字符串或直接写入csv文件。

基于之前答案的冗长，我们都应该感谢熊猫的捷径。