How to use a Pydantic model with Form data in FastAPI?
I found a solution that can help us to use Pydantic with FastAPI forms :)
My code:
class AnyForm(BaseModel):
any_param: str
any_other_param: int = 1
@classmethod
def as_form(
cls,
any_param: str = Form(...),
any_other_param: int = Form(1)
) -> AnyForm:
return cls(any_param=any_param, any_other_param=any_other_param)
@router.post('')
async def any_view(form_data: AnyForm = Depends(AnyForm.as_form)):
...
It's shown in the Swagger as a usual form.
It can be more generic as a decorator:
import inspect
from typing import Type
from fastapi import Form
from pydantic import BaseModel
from pydantic.fields import ModelField
def as_form(cls: Type[BaseModel]):
new_parameters = []
for field_name, model_field in cls.__fields__.items():
model_field: ModelField # type: ignore
new_parameters.append(
inspect.Parameter(
model_field.alias,
inspect.Parameter.POSITIONAL_ONLY,
default=Form(...) if not model_field.required else Form(model_field.default),
annotation=model_field.outer_type_,
)
)
async def as_form_func(**data):
return cls(**data)
sig = inspect.signature(as_form_func)
sig = sig.replace(parameters=new_parameters)
as_form_func.__signature__ = sig # type: ignore
setattr(cls, 'as_form', as_form_func)
return cls
And the usage looks like
class Test1(BaseModel):
a: str
b: int
@as_form
class Test(BaseModel):
param: str
test: List[Test1]
test1: Test1
b: int = 1
a: str = '2342'
@router.post('/me', response_model=Test)
async def me(request: Request, form: Test = Depends(Test.as_form)):
return form
you can use data-form like below:
@app.post("/form", response_model=SimpleModel)
def form_post(no: int = Form(...),nm: str = Form(...)):
return SimpleModel(no=no,nm=nm)
If you're only looking at abstracting the form data into a class you can do it with a plain class
from fastapi import Form, Depends
class AnyForm:
def __init__(self, any_param: str = Form(...), any_other_param: int = Form(1)):
self.any_param = any_param
self.any_other_param = any_other_param
def __str__(self):
return "AnyForm " + str(self.__dict__)
@app.post('/me')
async def me(form: AnyForm = Depends()):
print(form)
return form
And it can also be turned into a Pydantic Model
from uuid import UUID, uuid4
from fastapi import Form, Depends
from pydantic import BaseModel
class AnyForm(BaseModel):
id: UUID
any_param: str
any_other_param: int
def __init__(self, any_param: str = Form(...), any_other_param: int = Form(1)):
id = uuid4()
super().__init__(id, any_param, any_other_param)
@app.post('/me')
async def me(form: AnyForm = Depends()):
print(form)
return form