python data_error ai_generated true

pydantic_core._pydantic_core.ValidationError: 1 validation error for User Extra inputs are not permitted [type=extra_forbidden, input_value='admin', input_type=str]

ID: python/pydantic-v2-extra-input-forbidden

Also available as: JSON · Markdown · 中文
80%Fix Rate
88%Confidence
0Evidence
2024-03-12First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
2.x active — — —

Root Cause

In Pydantic v2, the default model_config no longer allows extra fields. Any key in the input dict that is not declared as a field triggers extra_forbidden.

generic

中文

在 Pydantic v2 中，默认 model_config 不再允许额外字段。输入字典中任何未声明的键都会触发 extra_forbidden 错误。

Workarounds

  1. 95% success 
    Declare the field explicitly on the model:

class User(BaseModel):
    name: str
    role: str = 'user'
  2. 90% success 
    If you intentionally want to accept unknown keys:

class User(BaseModel):
    model_config = ConfigDict(extra='ignore')
    name: str
  3. 85% success 
    For dynamic keys, use a dict field:

class User(BaseModel):
    name: str
    metadata: dict[str, Any] = {}

Dead Ends

Common approaches that don't work:

  1. 70% fail

    The extra data is silently discarded, so downstream code that relies on it raises KeyError or AttributeError later.

  2. 55% fail

    Fields become untyped Any attributes; validation is skipped and IDE/type-checker support is lost, causing subtle runtime bugs.

  3. 80% fail

    Loses v2 performance, Rust core, and breaks other dependencies that require v2.