Converting a json file to a python class-CodePudding

Consider the json (named h.json), want to convert this into a python dataclass.

{
    "acc1":{
        "email":"[email protected]",
        "password":"acc1",
        "name":"ACC1",
        "salary":1
    },
    "acc2":{
        "email":"[email protected]",
        "password":"acc2",
        "name":"ACC2",
        "salary":2
    }

}

I could always use an alternative constructor for getting each account, for example.

import json
from dataclasses import dataclass

@dataclass
class Account(object):
    email:str
    password:str
    name:str
    salary:int
    
    @classmethod
    def from_json(cls, json_key):
        file = json.load(open("h.json"))
        return cls(**file[json_key])

but this is limited to what arguments (email, name, etc.) were defined in the dataclass. What if I were to modify the json to include another thing, say age, the script would end up returning a TypeError, specifically TypeError: __init__() got an unexpected keyword argument 'age'. Is there a way to dynamically adjust the class attributes based on the keys of the dict (json object), so that I don't have to add attributes each time I add a new key to the json.

(PS: I'm new to python, coding in general)

CodePudding user response：

For a flat (not nested dataclass) the code below does the job.
If you need to handle nested dataclasses you should use a framework like dacite.
Note 1 that loading the data from the json file should not be part of your class logic.

Note 2 If your json can contain anything - you can not map it to a dataclass and you should have to work with a dict

from dataclasses import dataclass
from typing import List

data = {
    "acc1":{
        "email":"[email protected]",
        "password":"acc1",
        "name":"ACC1",
        "salary":1
    },
    "acc2":{
        "email":"[email protected]",
        "password":"acc2",
        "name":"ACC2",
        "salary":2
    }

}



@dataclass
class Account:
    email:str
    password:str
    name:str
    salary:int

accounts: List[Account] = [Account(**x) for x in data.values()]
print(accounts)

output

[Account(email='[email protected]', password='acc1', name='ACC1', salary=1), Account(email='[email protected]', password='acc2', name='ACC2', salary=2)]

CodePudding user response：

This way you lose some dataclass features.

Such as determining whether it is optional or not
Such as auto-completion feature

However, you are more familiar with your project and decide accordingly

There must be many methods, but this is one of them:

@dataclass
class Account(object):
    email: str
    password: str
    name: str
    salary: int

    @classmethod
    def from_json(cls, json_key):
        file = json.load(open("1.txt"))
        keys = cls.__dataclass_fields__.keys()
        json_data = file[json_key]
        normal_json_data = {key: json_data[key] for key in json_data if key in keys}
        anormal_json_data = {key: json_data[key] for key in json_data if key not in keys}
        tmp = cls(**normal_json_data)
        for anormal_key in anormal_json_data:
            setattr(tmp,anormal_key,anormal_json_data[anormal_key])
        return tmp

test = Account.from_json("acc1")
print(test.age)