如何使类 JSON 可序列化 [英] How to make a class JSON serializable
问题描述
如何使 Python 类可序列化?
一个简单的类:
类文件项:def __init__(self, fname):self.fname = fname
我应该怎么做才能获得以下输出:
<预><代码>>>>导入json>>>my_file = FileItem('/foo/bar')>>>json.dumps(my_file)类型错误:FileItem"类型的对象不是 JSON 可序列化的没有错误
您对预期的输出有什么想法吗?例如,这样做可以吗?
<预><代码>>>>f = FileItem("/foo/bar")>>>魔法(女)'{"fname": "/foo/bar"}'在这种情况下,您只能调用 json.dumps(f.__dict__)
.
如果你想要更多的自定义输出,那么你必须子类化 JSONEncoder
并实现您自己的自定义序列化.
一个简单的例子,见下文.
<预><代码>>>>从 json 导入 JSONEncoder>>>类 MyEncoder(JSONEncoder):定义默认(自我,o):返回 o.__dict__>>>MyEncoder().encode(f)'{"fname": "/foo/bar"}'然后你将这个类传递到 json.dumps()
方法为 cls
kwarg:
json.dumps(cls=MyEncoder)
如果您还想解码,则必须向 JSONDecoder
类.例如:
How to make a Python class serializable?
A simple class:
class FileItem:
def __init__(self, fname):
self.fname = fname
What should I do to be able to get output of:
>>> import json
>>> my_file = FileItem('/foo/bar')
>>> json.dumps(my_file)
TypeError: Object of type 'FileItem' is not JSON serializable
Without the error
Do you have an idea about the expected output? For example, will this do?
>>> f = FileItem("/foo/bar")
>>> magic(f)
'{"fname": "/foo/bar"}'
In that case you can merely call json.dumps(f.__dict__)
.
If you want more customized output then you will have to subclass JSONEncoder
and implement your own custom serialization.
For a trivial example, see below.
>>> from json import JSONEncoder
>>> class MyEncoder(JSONEncoder):
def default(self, o):
return o.__dict__
>>> MyEncoder().encode(f)
'{"fname": "/foo/bar"}'
Then you pass this class into the json.dumps()
method as cls
kwarg:
json.dumps(cls=MyEncoder)
If you also want to decode then you'll have to supply a custom object_hook
to the JSONDecoder
class. For example:
>>> def from_json(json_object):
if 'fname' in json_object:
return FileItem(json_object['fname'])
>>> f = JSONDecoder(object_hook = from_json).decode('{"fname": "/foo/bar"}')
>>> f
<__main__.FileItem object at 0x9337fac>
>>>
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