pythonfastapi

Why FastAPI cannot parse UUID by pattern while Regex101 can?

I have some FastAPI application:

from typing import Annotated

import uvicorn
from fastapi import FastAPI, Query
from pydantic import constr

app = FastAPI()


@app.get("search")
async def search(
    partner_ids: Annotated[
        constr(pattern="((^|[,])[0-9a-fA-F]{8}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{4}\b-[0-9a-fA-F]{12})+"),
        Query(),
    ] = "ca930bc7-f4cf-4b10-9c6f-7db13b6ab4f0",
):
    pass


if __name__ == "__main__":
    uvicorn.run("uuid_list:app", reload=True, port=8004)

The problem with it is validation of partner_ids does not work:

enter image description here

At the same time regex101 finds uuid:

enter image description here

What's wrong with FastAPI?

Upd. The regex is for comma separated list of uuids.

Solution

  • As @MatsLindh mentioned in the comment you can just use List[type]. In your case it will be:

    @app.get("search")
async def search(
    partner_ids: Annotated[List[UUID], Query(...)]
):
    pass

    It won't be a comma separated but at least it work out of a box.

    In your example it seems that you have in issue in regex. Try to set uuid pattern like this:

    UUIDPattern = constr(
    regex=r"^([0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12})(,[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12})*$"
)

@app.get("/search")
async def search(
    partner_ids: Annotated[UUIDListPattern], Query()],
):
    pass

    There is a third option using a schema:

    # Pydantic model for validating the input schema
class PartnerIDsSchema(BaseModel):
    partner_ids: str

    @validator('partner_ids')
    def check_uuids(cls, v):
        uuids = v.split(",")
        for uuid_str in uuids:
            try:
                UUID(uuid_str.strip())
            except ValueError:
                raise ValueError(f"Invalid UUID found: {uuid_str}")
        return v

@app.get("/search")
async def search(
    partner_ids: PartnerIDsSchema = Query(...)
):
    pass

    But you will need to convert then in actual uuids in the method itself because they will be passed as a single string.