Pydantic

May 16, 2024 | seedling, permanent

tags :

Python Apps #

URL Pydantic is the most widely used data validation library for Python.

github Data validation using Python type hints

Installing Pydantic is as simple as: pip install pydantic

from pydantic import BaseModel

class MyModel(BaseModel):
    a: int
    b: list[str]

m = MyModel(a=123, b=['a', 'b', 'c'])
print(m.model_dump())
#> 'a': 123, 'b': ['a', 'b', 'c']

Why use Pydantic? #

Powered by type hints #

— with Pydantic, schema validation and serialization are controlled by type annotations; less to learn, less code to write and integration with your IDE and static analysis tools.

Speed #

— Pydantic’s core validation logic is written in Rust, as a result Pydantic is among the fastest data validation libraries for Python.

JSON Schema #

— Pydantic models can emit JSON Schema allowing for easy integration with other tools.

Strict and Lax mode #

— Pydantic can run in either strict=True mode (where data is not converted) or strict=False mode where Pydantic tries to coerce data to the correct type where appropriate.

Dataclasses, TypedDicts and more #

— Pydantic supports validation of many standard library types including dataclass and TypedDict.

Customisation #

— Pydantic allows custom validators and serializers to alter how data is processed in many powerful ways.

Ecosystem #

— around 8,000 packages on PyPI use Pydantic, including massively popular libraries like

FastAPI,
huggingface/transformers (Hugging Face)
django-ninja
SQLModel, and
LangChain

Battle tested #

— Pydantic is downloaded >70m times/month and is used by all FAANG companies and 20 of the 25 largest companies on NASDAQ — if you’re trying to do something with Pydantic, someone else has probably already done it.