# fastapi.exceptions.ResponseValidationError: 1 validation error for Response\nvalue is not a valid dict (type=type_error.dict)

- **ID:** `python/fastapi-response-model-validation-error`
- **Domain:** python
- **Category:** data_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

响应模型与返回的数据类型不匹配。

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 3.x | active | — | — |

## Workarounds

1. **** (90% success)
   ```
   from pydantic import BaseModel\nclass Item(BaseModel):\n    name: str\n    price: float\n@app.get('/items/{id}', response_model=Item)\nasync def get_item(id: int):\n    return {'name': 'Foo', 'price': 10.5}
   ```
2. **** (85% success)
   ```
   app.get('/items', response_model=Item, response_model_exclude_unset=True)
   ```

## Dead Ends

- **** — 可能丢失数据或引发其他错误。 (60% fail)
- **** — 失去 API 文档和验证优势。 (70% fail)