Optional Body(...) parameter?

[charliegriefer]

Hey folks...

I have an API request (a POST) that currently takes one path var and two body vars as follows:

@api.post("/account/{account_id}/report", status_code=201)
def create_report(account_id: int, user_params: UserParams, report_type: str = Body(...)):

(UserParams is a pydantic BaseModel defined earlier in the script)

I now need to add another body param. Just a string. But it's optional.

I didn't see anything in the FastAPI docs that demonstrated an optional Body param, other than setting a BaseModel value to None.

I looked at the source code and saw that Body takes a Schema, but haven't been able to figure out how to make it optional or default it to None.

I tried:

def create_report(account_id: int, user_params: UserParams, report_type: str = Body(...), sf_rec_id: int = Body(..., default=None)):

But got the following exception:

TypeError: Body() got multiple values for argument 'default'

Any help would be greatly appreciated.

Thanks!

[charliegriefer]

sigh

Nevermind. Looks like this does it:

def create_report(account_id: int, user_params: UserParams, report_type: str = Body(...), sf_rec_id: str = Body(default=None)):

Out of curiosity, would anybody mind elaborating on the ... that gets passed in? It looks like I don't need to use it if I'm sending in a default value. I tried the other way because I saw importance: int = Body(..., gt=0), in the FastAPI docs, so assumed that the ... was necessary and any other args would follow. Clearly, that was incorrect :)

Thanks!

[tiangolo]

Thanks for reporting back and closing the issue.

The ... means "this is required", in contrast to None, not required, or a literal value "Foo", that means that "Foo" is the default.

[jibinmathew69]

You changed the datatype in the answer compared to the Question, but what if the optional data is supposed to be int/float and default value is None.

[igorbga]

@jibinmathew69 I don't understand your question.
If your default value is actually "None", then your type is not int/float, is Optional[int/float]. "..." would mean that the value is required meanwhile None would mean that actually your default value is None.

Of course this means you can not distinguise when a "myvalue: null" was sent and when directly "myvalue" was not set. I think this problem is quite extended when processing JSON input.

Pydantic models "solve" it by having control over unset values (https://fastapi.tiangolo.com/tutorial/body-updates/#partial-updates-with-patch), but I guess for "primitive" types you don't have such options.

Was that your question?

[bostrick]

I'm having similar issues... I'd like to define a body as either an arbitrary dict or just no body... I've tried variants such as...

ActionCommandParamsT = Annotated[dict[str, Any] |None, Body()]
ActionCommandParamsT = Annotated[dict[str, Any], Body()] | None
ActionCommandParamsT = Annotated[dict[str, Any], Body(default=None)]

but none seem to do the magic (the first two causing route confusion between Body() and Query() params, the latter just plain wrong.)

Anyone know some magic I"m missing? Thanks!