Implement a custom validator for a single Pydantic model field
WHAT IT TESTS: Your grasp of Pydantic v2 field validation hooks. ANSWER OUTLINE: Use @field_validator as a classmethod, raise ValueError on failure, return the value. RED FLAG: Validating outside the model or confusing v1 @validator with v2.
WHAT IT TESTS: Whether you understand Pydantic v2's extension points for field-level logic beyond standard type constraints. ANSWER OUTLINE: A strong answer leads with @field_validator as a classmethod, raises ValueError for passwords under 10 characters or missing a digit, returns the cleaned string, and optionally contrasts this with reusable Annotated validators using __get_pydantic_core_schema__.
Read the original → pydantic.dev
- #pydantic
- #fastapi
- #validation
- #python
- #field-validator
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