**Concurrency** and **parallelism** both relate to "different things happening more or less at the same time".

But the details between *concurrency* and *parallelism* are quite different.

To see the difference, imagine the following story about burgers:

### Concurrent Burgers

You go with your crush to get fast food, you stand in line while the cashier takes the orders from the people in front of you. 😍

- `UP-TO-DATE` - tasks that used incremental build and were not re-run.

To summarize:

1. First, we used the `build` task to populate our local cache with task inputs and outputs -- we can imagine this was done a week ago.
2. Then, we used the `clean` task to mimic switching branches -- overriding previous outputs.

```Python hl_lines="2"
{!../../../docs_src/python_types/tutorial001.py!}
```

### Edit it

It's a very simple program.

But now imagine that you were writing it from scratch.

At some point you would have started the definition of the function, you had the parameters ready...

But then you have to call "that method that converts the first letter to upper case".

# Security - First Steps

Let's imagine that you have your **backend** API in some domain.

And you have a **frontend** in another domain or in a different path of the same domain (or in a mobile application).

And you want to have a way for the frontend to authenticate with the backend, using a **username** and **password**.

We can use **OAuth2** to build that with **FastAPI**.

        Prefer to use the `Annotated` version if possible.

    ```Python hl_lines="13"
    {!> ../../../docs_src/query_params_str_validations/tutorial008.py!}
    ```

## Alias parameters

Imagine that you want the parameter to be `item-query`.

Like in:

```
http://127.0.0.1:8000/items/?item-query=foobaritems
```

But `item-query` is not a valid Python variable name.

Megalosaurus, forty feet long or so, waddling like an elephantine lizard up Holborn Hill. Smoke lowering down from chimney-pots, making a soft black drizzle, with flakes of soot in it as big as full-grown snowflakes—gone into mourning, one might imagine, for the death of the sun. Dogs, undistinguishable in mire. Horses, scarcely better; splashed to their very blinkers. Foot passengers, jostling one another’s umbrellas in a general infection of ill temper, and losing their foot-hold at street-corners,...

			// if this happens, then we know that this container was previously running and isn't anymore (assuming the CRI isn't failing to return running containers).
			// you can imagine this happening in cases where a container failed and the kubelet didn't ask about it in time to see the result.

  @Override
  public void tearDown() throws Exception {
    /*
     * Clear interrupt for future tests.
     *
     * (Ideally we would perform interrupts only in threads that we create, but
     * it's hard to imagine that anything will break in practice.)
     */
    clearInterrupt();
    aggregateFutureLogger.removeHandler(aggregateFutureLogHandler);
    super.tearDown();
  }

  /*

  @Override
  public void tearDown() throws Exception {
    /*
     * Clear interrupt for future tests.
     *
     * (Ideally we would perform interrupts only in threads that we create, but
     * it's hard to imagine that anything will break in practice.)
     */
    clearInterrupt();
    aggregateFutureLogger.removeHandler(aggregateFutureLogHandler);
    super.tearDown();
  }

  /*

func (l *Loader) AddInteriorSym(container Sym, interior Sym) {
	// Container symbols are expected to have content/data.
	// NB: this restriction may turn out to be too strict (it's possible
	// to imagine a zero-sized container with an interior symbol pointing
	// into it); it's ok to relax or remove it if we counter an
	// oddball host object that triggers this.
	if l.SymSize(container) == 0 && len(l.Data(container)) == 0 {