This is the code for an inventory manager, I started the API, checked if it was up, than ran a test file. I have been geting internal server errors, it’s saying db is not associated with a value but it is.

from fastapi import FastAPI, HTTPException, Depends
from systemfiles import db, models, schemas

app = FastAPI()

# Dependency injection for database session
def get_db():
    db = db.SessionLocal()
    try:
        yield db
    finally:
        db.close()

@app.get("/products/", response_model=list[schemas.product])
async def get_products(db: db.SessionLocal = Depends(get_db)):
    products = db.query(models.Product).all()
    return products

@app.post("/products/", response_model=schemas.product, status_code=201)
async def create_product(product: schemas.ProductCreate, db: db.SessionLocal = Depends(get_db)):
    db_product = models.Product(**product.model_dump())
    db.add(db_product)
    db.commit()
    db.refresh(db_product)
    return db_product

@app.get("/products/{product_id}", response_model=schemas.product)
async def get_product(product_id: int, db: db.SessionLocal = Depends(get_db)):
    product = db.query(models.Product).filter(models.Product.id == product_id).first()
    if not product:
        raise HTTPException(status_code=404, detail="Product not found")
    return product

everything seems ok but i have been getting this traceback in the uvicorn terminal :

ERROR:    Exception in ASGI application
Traceback (most recent call last):
  File "C:UsersRayaans LaptopAppDataLocalProgramsPythonPython312Libsite-packagesuvicornprotocolshttph11_impl.py", line 408, in run_asgi  
    result = await app(  # type: ignore[func-returns-value]
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:UsersRayaans LaptopAppDataLocalProgramsPythonPython312Libsite-packagesuvicornmiddlewareproxy_headers.py", line 84, in __call__  
    return await self.app(scope, receive, send)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:UsersRayaans LaptopAppDataLocalProgramsPythonPython312Libsite-packagesfastapiapplications.py", line 1106, in __call__
    await super().__call__(scope, receive, send)
  File "C:UsersRayaans LaptopAppDataLocalProgramsPythonPython312Libsite-packagesstarletteapplications.py", line 122, in __call__
    await self.middleware_stack(scope, receive, send)
  File "C:UsersRayaans LaptopAppDataLocalProgramsPythonPython312Libsite-packagesstarlettemiddlewareerrors.py", line 184, in __call__      
    raise exc
  File "C:UsersRayaans LaptopAppDataLocalProgramsPythonPython312Libsite-packagesstarlettemiddlewareerrors.py", line 162, in __call__      
    await self.app(scope, receive, _send)
  File "C:UsersRayaans LaptopAppDataLocalProgramsPythonPython312Libsite-packagesstarlettemiddlewareexceptions.py", line 79, in __call__   
    raise exc
  File "C:UsersRayaans LaptopAppDataLocalProgramsPythonPython312Libsite-packagesstarlettemiddlewareexceptions.py", line 68, in __call__   
    await self.app(scope, receive, sender)
  File "C:UsersRayaans LaptopAppDataLocalProgramsPythonPython312Libsite-packagesfastapimiddlewareasyncexitstack.py", line 20, in __call__ 
    raise e
  File "C:UsersRayaans LaptopAppDataLocalProgramsPythonPython312Libsite-packagesfastapimiddlewareasyncexitstack.py", line 17, in __call__ 
    await self.app(scope, receive, send)
  File "C:UsersRayaans LaptopAppDataLocalProgramsPythonPython312Libsite-packagesstarletterouting.py", line 718, in __call__
    await route.handle(scope, receive, send)
  File "C:UsersRayaans LaptopAppDataLocalProgramsPythonPython312Libsite-packagesstarletterouting.py", line 276, in handle
    await self.app(scope, receive, send)
  File "C:UsersRayaans LaptopAppDataLocalProgramsPythonPython312Libsite-packagesstarletterouting.py", line 66, in app
    response = await func(request)
               ^^^^^^^^^^^^^^^^^^^
  File "C:UsersRayaans LaptopAppDataLocalProgramsPythonPython312Libsite-packagesfastapirouting.py", line 264, in app
    solved_result = await solve_dependencies(
                    ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:UsersRayaans LaptopAppDataLocalProgramsPythonPython312Libsite-packagesfastapidependenciesutils.py", line 595, in solve_dependencies
    solved = await solve_generator(
             ^^^^^^^^^^^^^^^^^^^^^^
  File "C:UsersRayaans LaptopAppDataLocalProgramsPythonPython312Libsite-packagesfastapidependenciesutils.py", line 520, in solve_generator
    return await stack.enter_async_context(cm)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:UsersRayaans LaptopAppDataLocalProgramsPythonPython312Libcontextlib.py", line 647, in enter_async_context
    result = await _enter(cm)
             ^^^^^^^^^^^^^^^^
  File "C:UsersRayaans LaptopAppDataLocalProgramsPythonPython312Libcontextlib.py", line 204, in __aenter__
    return await anext(self.gen)
           ^^^^^^^^^^^^^^^^^^^^^
  File "C:UsersRayaans LaptopAppDataLocalProgramsPythonPython312Libsite-packagesfastapiconcurrency.py", line 36, in contextmanager_in_threadpool
    raise e
UnboundLocalError: cannot access local variable 'db' where it is not associated with a value

heres the code inside systemfiles/db.py:

from sqlalchemy import create_engine, Column, Integer, String, Float
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

# Create the database engine
engine = create_engine("sqlite:///inventory.db")

# Create a SessionLocal class for creating database sessions
SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)

# Create a base class for declarative models
Base = declarative_base()

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