CODEWITHSUNDEEP
pythonjsonpydanticdump
nottelling
nottelling

Reputation: 11

Pretty printing with pydantic json dump

I have a pydantic model with a 2D array that I’d like to pretty print when I dump it to a file with an indentation set at 4. For reference:

import json
from annotated_types import Len
from typing_extensions import Annotated 

from pydantic import BaseModel, Field, ConfigDict

TwoDim = Annotated[
   Sequence[float],
   Len(min_length=2, max_length=2),
]

class Tester(BaseModel):
    test_val: Sequence[TwoDim] = Field()

I have tried implementing a custom encoder and using the model’s ConfigDict:

# in the model definition 
    model_config = ConfigDict(
        json_encoders={
            TwoDim: NoIndentEncoder().encode
        }
    )

class NoIndentEncoder(json.JSONEncoder):
    def encode(self, obj):
        if isinstance(obj, list):
            return f”[{‘, ‘.join([json.dumps(elem) for elem in obj])}]”
        return super().encode(obj)

This almost gives me the right output (read as a json file):

{
    “test_val”: [
        “[0.0, 1.2]”,
        “[3.0, 1.4]”,

        …
    ]
}

But I don’t want each internal array to print with quotes.

Upvotes: 0

Views: 397

Answers (1)

emno
emno

Reputation: 191

This may work for you:

import json
from pydantic.json import pydantic_encoder

json.dump(your_pydantic_model.model_dump(), file_obj, default=pydantic.encoder, indent=4)

Upvotes: 1

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