You can probably skip this part.

///

There's an alternative way to define this logic to be executed during *startup* and during *shutdown*.

You can define event handlers (functions) that need to be executed before the application starts up, or when the application is shutting down.

This could be especially useful during testing, as it's very easy to override a dependency with your own custom settings.

### The config file { #the-config-file }

Coming from the previous example, your `config.py` file could look like:

{* ../../docs_src/settings/app02_an_py39/config.py hl[10] *}

    "price": 42.0,
    "tax": 3.2,
    "tags": ["rock", "metal", "bar"],
    "image": {
        "url": "http://example.com/baz.jpg",
        "name": "The Foo live"
    }
}
```

Again, doing just that declaration, with **FastAPI** you get:

* Editor support (completion, etc.), even for nested models
* Data conversion
* Data validation
* Automatic documentation

3. This `yield from` tells the function to iterate over that thing named `file_like`. And then, for each part iterated, yield that part as coming from this generator function (`iterfile`).

    So, it is a generator function that transfers the "generating" work to something else internally.

    By doing it this way, we can put it in a `with` block, and that way, ensure that the file-like object is closed after finishing.

/// tip

    /**
     * Constructs a JcifsEngine with the specified properties.
     *
     * @param props the properties for configuring the CIFS context
     * @throws CrawlingAccessException if an error occurs during initialization
     */
    public JcifsEngine(final Properties props) {
        try {
            cifsContext = new BaseContext(new PropertyConfiguration(props));
        } catch (final CIFSException e) {

    assertEscaping(xmlEscaper, "\uFFFD", '\uFFFF');

    assertEquals(
        "0xFFFE is forbidden and should be replaced during escaping",
        "[\uFFFD]",
        xmlEscaper.escape("[\ufffe]"));
    assertEquals(
        "0xFFFF is forbidden and should be replaced during escaping",
        "[\uFFFD]",
        xmlEscaper.escape("[\uffff]"));
  }

Up to now, you have been declaring the parts of the request that you need with their types.

Taking data from:

* The path as parameters.
* Headers.
* Cookies.
* etc.

And by doing so, **FastAPI** is validating that data, converting it and generating documentation for your API automatically.

But there are situations where you might need to access the `Request` object directly.

 * This class provides functionality to load, parse, and manage character mapping
 * rules that define how input characters should be transformed to output characters
 * during text analysis and search processing.
 *
 * Character mapping files contain mapping rules in the format:
 * input1,input2,... => output
 */
public class CharMappingFile extends DictionaryFile<CharMappingItem> {

In this case, `str` is the type parameter passed to `list`.

///

That means: "the variable `items` is a `list`, and each of the items in this list is a `str`".

By doing that, your editor can provide support even while processing items from the list:

<img src="/img/python-types/image05.png">

Without types, that's almost impossible to achieve.

    yield "s"
    raise ValueError("Broken after yield")


app = FastAPI()


@app.get("/catching")
def catching(d: Annotated[str, Depends(catching_dep)]) -> Any:
    raise CustomError("Simulated error during streaming")


@app.get("/broken")
def broken(d: Annotated[str, Depends(broken_dep)]) -> Any:
    return {"message": "all good?"}


client = TestClient(app)


def test_catching():