# pydantic.error_wrappers.ValidationError: 1 validation error for Item
response -> name
  str type expected (type=type_error.str)

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

## Root Cause

FastAPI 路径操作返回的数据类型与响应模型不匹配

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 3.9 | active | — | — |
| 3.10 | active | — | — |

## Workarounds

1. **确保返回数据与模型一致** (95% success)
   ```
   class Item(BaseModel):
    name: str
@app.get('/item', response_model=Item)
def get():
    return Item(name='test')
   ```
2. **使用 response_model_exclude_unset** (90% success)
   ```
   @app.get('/item', response_model=Item, response_model_exclude_unset=True)
def get():
    return {'name': 'test'}
   ```

## Dead Ends

- **禁用响应模型验证** — 失去了类型安全性 (70% fail)
- **返回原始字典而不使用模型** — 文档生成可能出错 (60% fail)