python - 使用python从JSON文件中提取部分数据

Question

我一直在尝试仅从 JSON 文件中提取某些数据。我设法解码了 JSON 并将想要的数据放入 python 字典中。当我打印出字典时，它显示了所有需要的数据，但是当我尝试将字典写入新文件时，只写入了最后一个对象。我无法理解的一件事也是为什么当我打印字典时我得到多个字典对象而不是我期望的 1 个对象。

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 my_dict 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'}

在文件test.json中输出:

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

另外我想知道为什么 dict 输出 'title': u'Diego Vel\xe1zquez'但是如果我去打印 my_dict.values()[2] 我得到的名字通常写成 Diego Velázquez。

非常感谢

Answer 1

您的代码为每个对象创建新的字典对象:

my_dict={}

此外，它会覆盖变量之前的内容。 m_dict 中的旧 字典已从内存中删除。

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)

打印字典对象旨在通过显示数据类型来帮助开发人员。在 u'Diego Vel\xe1zquez' 中，开头的 u 表示一个 Unicode 对象(字符串)。当打印对象 using 时，它会根据您操作系统中的当前语言设置进行解码。