This will be especially useful when you use it in a **large code base** where you use **the same dependencies** over and over again in **many *path operations***.

## To `async` or not to `async`

As dependencies will also be called by **FastAPI** (the same as your *path operation functions*), the same rules apply while defining your functions.

    assertThat(network).isNotEqualTo(g2);
  }

  // Node sets are the same, but edge sets differ.
  @Test
  public void equivalent_edgeSetsDiffer() {
    network.addEdge(N1, N2, E12);

    MutableNetwork<Integer, String> g2 = createNetwork(edgeType);
    g2.addEdge(N1, N2, E13);

    assertThat(network).isNotEqualTo(g2);
  }

  // Node/edge sets are the same, but node/edge connections differ due to edge type.
  @Test

    assertThat(network).isNotEqualTo(g2);
  }

  // Node sets are the same, but edge sets differ.
  @Test
  public void equivalent_edgeSetsDiffer() {
    network.addEdge(N1, N2, E12);

    MutableNetwork<Integer, String> g2 = createNetwork(edgeType);
    g2.addEdge(N1, N2, E13);

    assertThat(network).isNotEqualTo(g2);
  }

  // Node/edge sets are the same, but node/edge connections differ due to edge type.
  @Test

    protected List<String> getJvmArguments(Path rootDirectory) {
        if (rootDirectory != null) {
            // TODO: do this
            return null;
        }
        return null;
    }

    // TODO: same is in DefaultMavenParser!!! (duplication)
    @Override
    protected MavenOptions parseArgs(String source, List<String> args) throws ParserException {
        try {

/// info

The parameter `summary` is available in OpenAPI 3.1.0 and above, supported by FastAPI 0.99.0 and above.

///

## Overriding the defaults

Using the information above, you can use the same utility function to generate the OpenAPI schema and override each part that you need.

/// tip

Prefer to use the `Annotated` version if possible.

///

```Python hl_lines="17"
{!> ../../docs_src/dependencies/tutorial006.py!}
```

////

These dependencies will be executed/solved the same way as normal dependencies. But their value (if they return any) won't be passed to your *path operation function*.

/// tip

Some editors check for unused function parameters, and show them as errors.

## Conditional OpenAPI from settings and env vars

You can easily use the same Pydantic settings to configure your generated OpenAPI and the docs UIs.

For example:

{* ../../docs_src/conditional_openapi/tutorial001.py hl[6,11] *}

Here we declare the setting `openapi_url` with the same default of `"/openapi.json"`.

And then we use it when creating the `FastAPI` app.

query_or_cookie_extractor(["query_or_cookie_extractor"])

read_query["/items/"]

query_extractor --> query_or_cookie_extractor --> read_query
```

## Using the same dependency multiple times

If one of your dependencies is declared multiple times for the same *path operation*, for example, multiple dependencies have a common sub-dependency, **FastAPI** will know to call that sub-dependency only once per request.

# Path Parameters and Numeric Validations

In the same way that you can declare more validations and metadata for query parameters with `Query`, you can declare the same type of validations and metadata for path parameters with `Path`.

## Import Path

First, import `Path` from `fastapi`, and import `Annotated`:

//// tab | Python 3.10+

```Python hl_lines="1  3"
{!> ../../docs_src/path_params_numeric_validations/tutorial001_an_py310.py!}
```

The process that happens when your API app calls the *external API* is named a "callback". Because the software that the external developer wrote sends a request to your API and then your API *calls back*, sending a request to an *external API* (that was probably created by the same developer).