FASTAPI: what is the difference in setting optional fields?

February 3, 2022

i have 2 optional fields publish and ratings, here is my code

  class POST(BaseModel):
    title: str
    content: str
    published: bool = True
    rating: Optional[int] = None

They both result in optional field, so what is the difference between two?

if i try something like this, this also works

class POST(BaseModel):
    title: str
    content: str
    published: bool = True
    rating: int = None

>Solution :

I dont think there is any difference except for the fact that by using Optional Key word we explicitly telling that this parameter Is optional both in code and swagger.

Note that this is not the same concept as an optional argument, which is one that has a default. An optional argument with a default does not require the Optional qualifier on its type annotation just because it is optional. For example:

def foo(arg: int = 0) -> None:
    ...
On the other hand, if an explicit value of None is allowed, the use of Optional is appropriate, whether the argument is optional or not. For example:

def foo(arg: Optional[int] = None) -> None:
    ...