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。我设法将JSON解码并将所需的数据放入python
dict中。当我打印出字典时，它会显示所有所需的数据，但是当我尝试将字典写入新文件时，只会写入最后一个对象。我不明白的一件事也是为什么当我打印字典时会得到多个字典对象而不是我期望的1。

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"}

我也想知道为什么字典会输出’title’：u’DiegoVel\xe1zquez’，但是如果我去打印my_dict.values（）[2]，我会把名字正常地写成DiegoVelázquez。

非常感谢

Answer 1

您的代码为每个对象创建新的字典对象，其中包括：

my_dict={}

此外，它会覆盖变量的先前内容。 m_dict中的 旧 字典将从内存中删除。 __

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, output_file)

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， u
开头表示Unicode对象（字符串）。打印使用对象时，将根据操作系统中当前的语言设置对其进行解码。