# `Response` class

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*.

Read more about it in the [FastAPI docs about returning a custom Response](https://fastapi.tiangolo.com/advanced/response-directly/#returning-a-custom-response)

    /*
     * Adapted from Hacker's Delight, Figure 11-1.
     *
     * Using DoubleUtils.bigToDouble, getting a double approximation of x is extremely fast, and
     * then we can get a double approximation of the square root. Then, we iteratively improve this
     * guess with an application of Newton's method, which sets guess := (guess + (x / guess)) / 2.
     * This iteration has the following two properties:
     *

	// Return false for methods other than GET and HEAD.
	if r.Method != http.MethodPut {
		return false
	}
	// If the object doesn't have a modtime (IsZero), or the modtime
	// is obviously garbage (Unix time == 0), then ignore modtimes
	// and don't process the If-Modified-Since header.
	if objInfo.ModTime.IsZero() || objInfo.ModTime.Equal(time.Unix(0, 0)) {
		return false
	}

The first step is to install FastAPI.

Make sure you create a [virtual environment](../virtual-environments.md), activate it, and then **install FastAPI**:

<div class="termy">

```console
$ pip install "fastapi[standard]"

---> 100%
```

</div>

/// note

    assertFullyRead(reader);

    // reset, skip, mark, then read the rest
    reader.reset();
    assertEquals(5, reader.skip(5));
    reader.mark(Integer.MAX_VALUE);
    assertThat(readFully(reader)).isEqualTo(string.substring(5));
    assertFullyRead(reader);

    // reset to the mark and then read the rest
    reader.reset();
    assertThat(readFully(reader)).isEqualTo(string.substring(5));

But documentation is still missing. Then APISpec was created.

It is a plug-in for many frameworks (and there's a plug-in for Starlette too).

The way it works is that you write the definition of the schema using YAML format inside the docstring of each function handling a route.

And it generates OpenAPI schemas.

That's how it works in Flask, Starlette, Responder, etc.

=========================

This module integrates mockwebserver3.MockWebServer with JUnit 4.

To use, first add this library as a test dependency:

```
testImplementation("com.squareup.okhttp3:mockwebserver3-junit4:5.3.0")
```

Then in tests annotated `@org.junit.Test`, you may declare a field with the `@Rule` annotation:

```
@Rule public final MockWebServerRule serverRule = new MockWebServerRule();
```

  N=$(echo "${cmd}" |sed 's,%patch\([0-9]\+\).*,\1,')
  file=$(grep "Patch$N:" "${SPEC}" |sed 's,.*: ,,')
  parg=$(echo "${cmd}" |sed 's,.*\(-p[0-9]\).*,\1,')
  if [[ ! "${file}" =~ doxygen && "${cmd}" != \#* ]]; then
    echo "patch ${parg} -s < ${file}"
    patch ${parg} -s < "${file}"
  fi

{* ../../docs_src/stream_json_lines/tutorial001_py310.py ln[27:30] hl[28] *}

### No Return Type { #no-return-type }

You can also omit the return type. FastAPI will then use the [`jsonable_encoder`](./encoder.md) to convert the data to something that can be serialized to JSON and then send it as JSON Lines.

{* ../../docs_src/stream_json_lines/tutorial001_py310.py ln[33:36] hl[34] *}

## Server-Sent Events (SSE) { #server-sent-events-sse }

	if s1.Mode()&os.ModeSymlink != 0 {
		return false
	}

	s2, err := os.Lstat(filepath.Dir(strings.TrimSuffix(path, "/")))
	if err != nil {
		return false
	}

	// If the directory has a different device as parent, then it is a mountpoint.
	ss1, ok1 := s1.Sys().(*syscall.Stat_t)
	ss2, ok2 := s2.Sys().(*syscall.Stat_t)
	return ok1 && ok2 &&
		// path/.. on a different device as path
		(ss1.Dev != ss2.Dev ||