Many packages that simplify it a lot have to make many compromises with the data model, database, and available features. And some of these packages that simplify things too much actually have security flaws underneath.

---

**FastAPI** doesn't make any compromise with any database, data model or tool.

It gives you all the flexibility to choose the ones that fit your project the best.

$ python main.py

I solemnly swear 🐺
```

</div>

## Alternatives { #alternatives }

This is a simple guide to get you started and teach you how everything works **underneath**.

There are many **alternatives** to managing virtual environments, package dependencies (requirements), projects.

```Python
with open("./somefile.txt") as f:
    contents = f.read()
    print(contents)
```

Underneath, the `open("./somefile.txt")` creates an object that is called a "Context Manager".

When the `with` block finishes, it makes sure to close the file, even if there were exceptions.

Import `SQLModel` and create a database model:

{* ../../docs_src/sql_databases/tutorial001_an_py310.py ln[1:11] hl[7:11] *}

The `Hero` class is very similar to a Pydantic model (in fact, underneath, it actually *is a Pydantic model*).

There are a few differences:

### <a href="https://www.django-rest-framework.org/" class="external-link" target="_blank">Django REST Framework</a> { #django-rest-framework }

Django REST framework was created to be a flexible toolkit for building Web APIs using Django underneath, to improve its API capabilities.

It is used by many companies including Mozilla, Red Hat and Eventbrite.

If you are using a Python version below 3.10, here's a tip from my very **subjective** point of view:

* 🚨 Avoid using `Optional[SomeType]`
* Instead ✨ **use `Union[SomeType, None]`** ✨.

Both are equivalent and underneath they are the same, but I would recommend `Union` instead of `Optional` because the word "**optional**" would seem to imply that the value is optional, and it actually means "it can be `None`", even if it's not optional and is still required.

    So, it's important to put this **near the end** of the `Dockerfile`, to optimize the container image build times.

6. Set the **command** to use `fastapi run`, which uses Uvicorn underneath.

    `CMD` takes a list of strings, each of these strings is what you would type in the command line separated by spaces.

## Very Technical Details { #very-technical-details }

/// warning

You can probably skip this.

These are very technical details of how **FastAPI** works underneath.

If you have quite some technical knowledge (coroutines, threads, blocking, etc.) and are curious about how FastAPI handles `async def` vs normal `def`, go ahead.

///

  //    places you'll have monitor.enter()/monitor.leave() and other
  //    places you'll have guard.enter()/guard.leave() even though
  //    it's the same lock being acquired underneath. Always using
  //    monitor.enterXXX()/monitor.leave() will make it really clear
  //    which lock is held at any point in the code.
  //
  // 3. I think "enterWhen(notEmpty)" reads better than "notEmpty.enter()".