```Python hl_lines="5-6"
{!../../docs_src/dependencies/tutorial007.py!}
```

/// tip

You can use `async` or regular functions.

**FastAPI** will do the right thing with each, the same as with normal dependencies.

///

## A dependency with `yield` and `try`

If you use a `try` block in a dependency with `yield`, you'll receive any exception that was thrown when using the dependency.

```console
$ echo "*" > .venv/.gitignore
```

</div>

/// details | What that command means

* `echo "*"`: will "print" the text `*` in the terminal (the next part changes that a bit)
* `>`: anything printed to the terminal by the command to the left of `>` should not be printed but instead written to the file that goes to the right of `>`
* `.gitignore`: the name of the file where the text should be written

    return unsafeCompare(comparator, a, b);
  }

  static int unsafeCompare(Comparator<?> comparator, Object a, @CheckForNull Object b) {
    // Pretend the comparator can compare anything. If it turns out it can't
    // compare a and b, we should get a CCE or NPE on the subsequent line. Only methods
    // that are spec'd to throw CCE and NPE should call this.
    @SuppressWarnings({"unchecked", "nullness"})

     * parts other than the last may begin with a digit (for example, "3com.com"). It's important to
     * disallow an initial digit in the last part; it's the only thing that stops an IPv4 numeric
     * address like 127.0.0.1 from looking like a valid domain name.
     */

    if (isFinalPart && DIGIT_MATCHER.matches(part.charAt(0))) {
      return false;
    }

       * parameters. If it were statically checked, the checker would still be OK with it, since
       * we're copying into a `contents` array whose type allows it to contain nulls. Still, it's
       * worth noting that we promise not to put nulls into the array in the first `size` elements.
       * We uphold that promise here because our callers promise that `elements` will not contain
       * nulls in its first `n` elements.
       */

			merged = append(merged, a[0])
			a = a[1:]
		default:
			merged = append(merged, b[0])
			b = b[1:]
		}
		if limit > 0 && len(merged) >= limit {
			break
		}
	}
	// Append anything left.
	if limit < 0 || len(merged) < limit {
		merged = append(merged, a...)
		merged = append(merged, b...)
	}
	m.o = merged
}

///

/// check | "**FastAPI** uses it to"

Handle all the core web parts. Adding features on top.

The class `FastAPI` itself inherits directly from the class `Starlette`.

So, anything that you can do with Starlette, you can do it directly with **FastAPI**, as it is basically Starlette on steroids.

///

### <a href="https://www.uvicorn.org/" class="external-link" target="_blank">Uvicorn</a>

 *   <li>The documentation style for testcases is to provide as javadoc a simple sentence or two
 *       describing the property that the testcase method purports to test. The javadocs do not say
 *       anything about how the property is tested. To find out, read the code.
 *   <li>These tests are "conformance tests", and do not attempt to test throughput, latency,

   * ImmutableList.copyOf} and use that list instead.
   */
  public List<Integer> asList() {
    /*
     * Typically we cache this kind of thing, but much repeated use of this view is a performance
     * anti-pattern anyway. If we cache, then everyone pays a price in memory footprint even if
     * they never use this method.
     */
    return new AsList(this);

  }

  /**
   * Evaluates whether the argument is an "IPv4 mapped" IPv6 address.
   *
   * <p>An "IPv4 mapped" address is anything in the range ::ffff:0:0/96 (sometimes written as
   * ::ffff:0.0.0.0/96), with the last 32 bits interpreted as an IPv4 address.
   *
   * <p>For more on IPv4 mapped addresses see section 2.5.5.2 of <a target="_parent"