使用python从JSON文件中提取部分数据

我一直试图从JSON文件中只提取某些数据。我设法解码了JSON并将想要的数据写入python dict。当我打印出dict时，它会显示所有想要的数据，但当我尝试将dict写入新文件时，只会写入最后一个对象。 我不明白的一件事是，为什么当我打印dict时，会得到多个dicts对象，而不是我所期望的1个

我的代码：

import json
input_file=open('json.json', 'r')
output_file=open('test.json', 'w')
json_decode=json.load(input_file)
for item in json_decode:
    my_dict={}
    my_dict['title']=item.get('labels').get('en').get('value')
    my_dict['description']=item.get('descriptions').get('en').get('value')
    my_dict['id']=item.get('id')
    print my_dict
back_json=json.dumps(my_dict, output_file)
output_file.write(back_json)
output_file.close() 

我的json.json文件：

[
{"type":"item","labels":{"en":{"language":"en","value":"George Washington"}},"descriptions":{"en":{"language":"en","value":"American politician, 1st president of the United States (in office from 1789 to 1797)"}},"id":"Q23"},
{"type":"item","aliases":{"en":[{"language":"en","value":"Douglas Noël Adams"},{"language":"en","value":"Douglas Noel Adams"}]},"labels":{"en":{"language":"en","value":"Douglas Adams"}},"descriptions":{"en":{"language":"en","value":"English writer and humorist"}},"id":"Q42"},
{"type":"item","aliases":{"en":[{"language":"en","value":"George Bush"},{"language":"en","value":"George Walker Bush"}]},"labels":{"en":{"language":"en","value":"George W. Bush"}},"descriptions":{"en":{"language":"en","value":"American politician, 43rd president of the United States from 2001 to 2009"}},"id":"Q207"},
{"type":"item","aliases":{"en":[{"language":"en","value":"Velázquez"},{"language":"en","value":"Diego Rodríguez de Silva y Velázquez"}]},"labels":{"en":{"language":"en","value":"Diego Velázquez"}},"descriptions":{"en":{"language":"en","value":"Spanish painter who was the leading artist in the court of King Philip IV"}},"id":"Q297"},
{"type":"item","labels":{"en":{"language":"en","value":"Eduardo Frei Ruiz-Tagle"}},"descriptions":{"en":{"language":"en","value":"Chilean politician and former President"}},"id":"Q326"}
]

打印我的命令输出：

{'id': u'Q23', 'description': u'American politician, 1st president of the United States (in office from 1789 to 1797)', 'title': u'George Washington'}
{'id': u'Q42', 'description': u'English writer and humorist', 'title': u'Douglas Adams'}
{'id': u'Q207', 'description': u'American politician, 43rd president of the United States from 2001 to 2009', 'title': u'George W. Bush'}
{'id': u'Q297', 'description': u'Spanish painter who was the leading artist in the court of King Philip IV', 'title': u'Diego Vel\xe1zquez'}
{'id': u'Q326', 'description': u'Chilean politician and former President', 'title': u'Eduardo Frei Ruiz-Tagle'}

文件test.json中的输出：

{"id": "Q326", "description": "Chilean politician and former President", "title": "Eduardo Frei Ruiz-Tagle"}

我还想知道为什么dict会输出“title”：u'Diego Vel\xe1zquez' 但是如果我去打印我的dict.values（）[2]我的名字通常写为迭戈·贝拉斯克斯

非常感谢您这样做：

for item in json_decode:

您正在循环文件中的每一行

每次通过循环时，您都重写my_dict变量，这就是为什么您的输出中只有一行

加载文件后，只需打印

json\u decode

变量即可

---

您的代码为每个对象创建新的dictionary对象，其中包含：

my_dict={}

此外，它还会覆盖变量的先前内容。默多克词典中的旧词典已从内存中删除

尝试在for循环之前创建一个列表，并将结果存储在那里

result = []
for item in json_decode:
    my_dict={}
    my_dict['title']=item.get('labels').get('en').get('value')
    my_dict['description']=item.get('descriptions').get('en').get('value')
    my_dict['id']=item.get('id')
    print(my_dict)
    result.append(my_dict)

最后，将结果写入输出：

back_json=json.dumps(result)

---

打印dictionary对象的目的是通过显示数据的类型来帮助开发人员。在u'Diego Vel\xe1zquez'中，开头的u表示Unicode对象（字符串）。打印object using时，将根据操作系统中的当前语言设置对其进行解码。

u'Diego Vel\xe1zquez'是Unicode的Python表示形式，其中\xe1是字符á。关于第二个问题：如果打印dict，则会得到字符串（repr）的Python表示形式，而打印字符串则会得到“正常”代表性（str）。有关更多信息，请查看“repr”和“str”（）