How to do GET request query parameter database validation which depends on multiple other query params.

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Example Code

from fastapi import FastAPI
import datetime

app = FastAPI()

@app.get("/clinic/available/doctors/list/")
def get_supplier_available_experts_list_on_clinic(clinic_id: str, supplier_id: str, date: datetime.date):
    """Return the list of the experts for a given supplier to a given clinic on a specific date."""
    return {"experts": []}

Description

On my above code you can see the function get_supplier_available_experts_list_on_clinic() takes three URL parameters. One of them is clinic_id, one is supplier_id and other is a valid date. The function does some internal calculations to generated the list of available experts for a specific supplier to a specific clinic on a given date.

The problem is I want to validate the three parameters as follows:

• There must be a valid clinic on the Database for the inputted Clinic ID
• There must be a valid supplier on the Database for the inputted Supplier ID
• There must be a relation between the Clinic and the Supplier on the Database
• There must be a valid schedule for the Clinic and for the Supplier on the Database for the given Date

Currently, I can do these validations checkups on my internal scripts but I want to do it on the parameter level like using some Dependencies or other mechanisms. Is it currently possible with the FastAPI?

Operating System

macOS

Operating System Details

No response

FastAPI Version

0.77.1

Python Version

3.10.2

Additional Context

Current Database: PostgreSQL 14

[aboubacs]

Validators don’t seem like a valid place for your use case. If you don’t want to implement your parameter validation logic in your endpoint (I’m not exactly sure why in the first place ?), you could do it with the dependency system. For example, instead of depending on “clinic_id”, your endpoint can depend on “clinic”, which depends on the database and a clinic_id (and raises an error if the clinic doesn’t exist).

Some sample code would be:

def get_db():
    try:
        db = your_function_to_get_a_database_session()
        yield db
    finally:
        db.close()


def get_clinic(db = Depends(get_db), clinic_id: str):
    # Reads the clinic from clinic_id
    # Raises an exception if the clinic doesn't exist

@app.get("/clinic/available/doctors/list/")
def get_supplier_available_experts_list_on_clinic(clinic: Depends(get_clinic), .......)
    .......

[acidjunk]

You could probably use a pydantic validator: to do some heavy lifting. https://pydantic-docs.helpmanual.io/usage/validators/

But considering that 2 of them need a DB (and a valid record) -> it would probably be good to raise 404 error’s when the ID don’t exist. And 422 when the relation doesn’t exist?

So IMO: it also depends on how you want to design your API.