function from_dict() failing for unknown reason in python

Question

I converted below JSON using https://json2csharp.com/code-converters/json-to-python to a dataclass:

{
"bypassCd": [
            "Duis sint ipsum in",
            "consequat"
          ] 
}

It generaged below dataclass – for some reason, it is showing error at .from_dict() method and I’m unable to figure it out. Please advise

from typing import List
from typing import Any
from dataclasses import dataclass
import json

@dataclass
class Root:
    bypassCd: List[str]

    @staticmethod
    def from_dict(obj: Any) -> 'Root':
        _bypassCd = [.from_dict(y) for y in obj.get("bypassCd")]
        return Root(_bypassCd)


# Example Usage
jsonstring = json.loads(''' 
{
        "bypassCd": [
            "Duis sint ipsum in",
            "consequat"
        ] }
''')

root = Root.from_dict(jsonstring)
print(root)

error:

 File "/local_home/afxx1285/pyprograms/test2.py", line 11
    _bypassCd = [.from_dict(y) for y in obj.get("bypassCd")]
                 ^
 SyntaxError: invalid syntax

Asked By: jimsweb

||

Source

Answer 1

You are getting a SyntaxError on this line:

_bypassCd = [.from_dict(y) for y in obj.get("bypassCd")]

… because you are trying to run the method/function from_dict, but you haven’t written which object holds this function. You could specify an object like this before the function call:

obj.from_dict(y)

I think what you want to do is recursively call the Root.from_dict function, so you should probably write:

Root.from_dict(y)

This still throws an error since your algorithm needs some changes, but this answers your initial question.

Answered By: Xiddoc

Answer 2

This is what I came up with, but it’s hard to say if it fits your needs. I can’t understand why it’s trying some recursion calling from_dict from inside from_dict.

from typing import Mapping, List
from dataclasses import dataclass
import json

@dataclass
class Root:
    bypassCd: List[str]

    @staticmethod
    def from_dict(obj: Mapping) -> 'Root':
        _bypassCd = obj.get("bypassCd", [])
        return Root(_bypassCd)


# Example Usage
my_dict = json.loads('''
{
    "bypassCd": [
        "Duis sint ipsum in",
        "consequat"
    ]
}
''')

root = Root.from_dict(my_dict)
print(root)

Answered By: liberforce

function from_dict() failing for unknown reason in python

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