How to convert Python dataclass to dictionary of string literal?

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Given a dataclass like below:

class MessageHeader(BaseModel):
    message_id: uuid.UUID

    def dict(self, **kwargs):
        return json.loads(self.json())

I would like to get a dictionary of string literal when I call dict on MessageHeader The desired outcome of dictionary is like below:

{'message_id': '383b0bfc-743e-4738-8361-27e6a0753b5a'}

I want to avoid using 3rd party library like pydantic & I do not want to use json.loads(self.json()) as there are extra round trips

Is there any better way to convert a dataclass to a dictionary with string literal like above?

python-dataclasses dictionary python json
2 Answers

You can use dataclasses.asdict:

from dataclasses import dataclass, asdict

class MessageHeader(BaseModel):
    message_id: uuid.UUID

    def dict(self):
        return {k: str(v) for k, v in asdict(self).items()}

If you're sure that your class only has string values, you can skip the dictionary comprehension entirely:

class MessageHeader(BaseModel):
    message_id: uuid.UUID

    dict = asdict
user_29887300

Use dataclasses.fields to create a shallow copy of fields and values.

from dataclasses import dataclass, fields
import uuid

@dataclass
class MessageHeader:
    message_id: uuid.UUID
    other_string: str

    def dict(self):
        return {field.name: str(getattr(self, field.name)) for field in fields(self)}

message_header = MessageHeader(uuid.uuid4(), "test_str")
print(message_header.dict())
user_37608040
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