PythonFastAPI dùng Pydantic model để tự động validate request body, query params, path params.
Trả về 422 Unprocessable Entity nếu invalid.
python
from pydantic import BaseModel, EmailStr, Field, field_validator
class UserCreate(BaseModel):
name: str = Field(min_length=2, max_length=50)
email: EmailStr
age: int = Field(ge=0, le=150)
@field_validator('name')
@classmethod
def name_alpha(cls, v: str) -> str:
if not v.replace(' ', '').isalpha():
raise ValueError('Only letters allowed')
return v.strip().title()
model_config = {"from_attributes": True} # Pydantic v2
@app.post("/users", status_code=201)
async def create_user(user: UserCreate): # Auto-validated!
...FastAPI uses Pydantic to auto-validate request body, query params, path params.
Returns 422 if invalid.
python
from pydantic import BaseModel, Field
class Item(BaseModel):
name: str = Field(min_length=1)
price: float = Field(gt=0)
quantity: int = Field(ge=0)
@app.post("/items")
async def create(item: Item): # Auto-validated
...