Pydantic
Python's de facto data validation library. Type-hint-driven models, fast Rust-based core (v2), and the foundation of FastAPI, LangChain, and most Python AI tooling.
Pydantic uses Python type hints to define data models with full runtime validation. v2 rewrote the core in Rust, making it one of the fastest validation libraries in any language. It is the validation layer under FastAPI, the structured-output spec for OpenAI's Python SDK, the schema layer for LangChain tools, and the backbone of Pydantic AI. If you do anything with structured data in Python, you reach for Pydantic.
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Python's de facto data validation library. Type-hint-driven models, fast Rust-based core (v2), and the foundation of FastAPI, LangChain, and most Python AI tooling.
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