FastAPI error: ImportError: attempting relative import with no known parent package

The Problem

I’m trying to split my FastAPI application’s code into different files, but I keep getting this error when I try to import them into main.py:

ImportError: attempted relative import with no known parent package

The import line at the top of main.py looks like this:

from . import schemas, models

My directory structure looks like this:

├── main.py
├── models.py
└── schemas.py

The directory’s name is app, and I’ve also tried the following import statement:

from app import schemas, models

This produces a different error:

ModuleNotFoundError: No module named 'app'

How do I successfully import models.py and schemas.py into main.py?

The Solution

When importing Python files in the same directory, we should not need to use from. The following import statement will work in main.py:

import schemas, models

If we later want to introduce additional organization to the project, such as placing schemas.py and models.py in a lib subdirectory, we will be able to import them as below:

import lib.schemas, lib.models

For more about importing local Python files in different directory structures, please see this answer.