You can declare a parameter in a *path operation function* or dependency to be of type `Response` and then you can set data for the response like headers or cookies.

You can also use it directly to create an instance of it and return it from your *path operations*.

You can import it directly from `fastapi`:

```python
from fastapi import Response
```

* **FastAPI**:
    * The same way that Starlette uses Uvicorn and cannot be faster than it, **FastAPI** uses Starlette, so it cannot be faster than it.

// stand-in for either complex type: complex64 or complex128.
type ComplexType complex64

// The append built-in function appends elements to the end of a slice. If
// it has sufficient capacity, the destination is resliced to accommodate the
// new elements. If it does not, a new underlying array will be allocated.
// Append returns the updated slice. It is therefore necessary to store the

   * this method should cause a call to {@link #notifyStarted()}, either during this method's run,
   * or after it has returned. If startup fails, the invocation should cause a call to {@link
   * #notifyFailed(Throwable)} instead.
   *
   * <p>This method should return promptly; prefer to do work on a different thread where it is
   * convenient. It is invoked exactly once on service startup, even when {@link #startAsync} is
   * called multiple times.

  private final Iterator<? extends ByteSource> it;
  private @Nullable InputStream in;

  /**
   * Creates a new instance.
   *
   * @param it an iterator of I/O suppliers that will provide each substream
   */
  public MultiInputStream(Iterator<? extends ByteSource> it) throws IOException {
    this.it = checkNotNull(it);
    advance();
  }

  @Override

     * exception, and wrongly believes that its exception is new (leading it to logging it when it
     * shouldn't)
     *
     * Our solution is for threads to CAS seenExceptionsField from null to a Set populated with _the
     * initial exception_, no matter which thread does the work. This ensures that
     * seenExceptionsField always contains not just the current thread's exception but also the

Then set Cookies in it, and then return it:

{* ../../docs_src/response_cookies/tutorial001.py hl[10:12] *}

/// tip

Keep in mind that if you return a response directly instead of using the `Response` parameter, FastAPI will return it directly.

So, you will have to make sure your data is of the correct type. E.g. it is compatible with JSON, if you are returning a `JSONResponse`.

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   * this method should cause a call to {@link #notifyStarted()}, either during this method's run,
   * or after it has returned. If startup fails, the invocation should cause a call to {@link
   * #notifyFailed(Throwable)} instead.
   *
   * <p>This method should return promptly; prefer to do work on a different thread where it is
   * convenient. It is invoked exactly once on service startup, even when {@link #startAsync} is
   * called multiple times.

Swagger UI will handle it behind the scenes for you, but it needs this "redirect" helper.

///

### Create a *path operation* to test it { #create-a-path-operation-to-test-it }

Now, to be able to test that everything works, create a *path operation*: