python runtime_error ai_generated true

PydanticUserError: `@validator` cannot be applied to instance methods. Use `@field_validator` instead.

ID: python/fastapi-pydantic-v2-validator-removed

Also available as: JSON · Markdown · 中文
80%Fix Rate
88%Confidence
0Evidence
2024-04-18First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
3.x active — — —

Root Cause

Code written for Pydantic v1 uses the removed `validator` decorator under Pydantic v2.

generic

中文

为 Pydantic v1 编写的代码在 Pydantic v2 下使用了已移除的 `validator` 装饰器。

Workarounds

  1. 92% success 
    Migrate to field_validator:
from pydantic import field_validator
@field_validator('name')
@classmethod
def check(cls, v): ...
  2. 85% success 
    Use bump-pydantic to automate migration.

Dead Ends

Common approaches that don't work:

  1. 60% fail

    FastAPI 0.100+ expects v2; downgrading causes other incompatibilities.

  2. 70% fail

    Loses validation logic and may accept bad data.