python data_error ai_generated true

HTTP/1.1 422 Unprocessable Entity {"detail":[{"loc":["body","age"],"msg":"value is not a valid integer","type":"type_error.integer"}]}

ID: python/fastapi-422-unprocessable-entity

Also available as: JSON · Markdown · 中文
80%Fix Rate
88%Confidence
0Evidence
2024-12-02First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
0.100.x active — — —
0.110.x active — — —

Root Cause

Client sent a value whose type does not match the Pydantic field (e.g., string for int, null for non-optional).

generic

中文

客户端发送的值与 Pydantic 字段类型不匹配（例如给 int 传字符串，给非可选字段传 null）。

Workarounds

  1. 95% success 
    Use `age: int = Field(..., ge=0)` and document; client should send `{"age": 30}` not `{"age": "30"}` unless using `model_config = ConfigDict(coerce_numbers_to_str=False)` with custom validator.
  2. 90% success 
    Add a custom validator: `@field_validator('age', mode='before') def coerce(cls, v): return int(v)`

Dead Ends

Common approaches that don't work:

  1. 90% fail

    Validation runs before the handler; decorator status does not apply.

  2. 70% fail

    Hides the real cause; clients still send wrong types.